Biological Exuberance

APES

Bonobos live in communities composed of large mixed-sex and mixed-age groups containing up to 60 or more individuals. These often divide into smaller, temporary subgroups that have a more fluid membership. On reaching adolescence (and becoming sexually mature), female Bonobos typically leave their home group and emigrate to a new one, while males usually remain in their home group for life. Females often form strongly bonded subgroups and are generally dominant to males. The mating system is promiscuous: males and females mate with multiple partners, and males do not generally participate extensively in raising their offspring.

Behavioral Expression: Bonobos have one of the most varied and extensive repertoires of homosexual practices found in any animal. Females engage in an extraordinary form of mutual genital stimulation that, in many aspects, is unique to this species. Sometimes known as GG-RUBBING (for genito-genital rubbing), this behavior is usually performed in a face-to-face embracing position (heterosexual copulation is also sometimes done in this position, but not as often as in lesbian interactions). One female stands on all fours and literally “carries” or lifts her partner off the ground; the female on the bottom wraps her legs around the other’s waist and clings to her as they rapidly rub their genitals against one another, directly stimulating each other’s clitoris. Some scientists believe that the particular shape and location of the Bonobo’s genitals have evolved specifically for lesbian rather than heterosexual interactions. During GG-rubbing, each female rhythmically swings her pelvis from side to side—precisely timed so that each partner is thrusting in opposite directions—at a rate of about two thrusts per second. This is comparable to the thrusting rate seen in males during heterosexual interactions, but males thrust vertically rather than sideways. In addition, although both homosexual and heterosexual copulations are quite brief, same-sex interactions generally last slightly longer—an average of about 15 seconds (maximum of 1 minute) compared to about 12 seconds (maximum of 45 seconds) for heterosexual matings. Sometimes females GG-rub with the same partner several times in a row.

As shown by their facial expressions, vocalizations, and genital engorgement, females experience intense pleasure—and probably orgasm—during homosexual interactions. Partners gaze intensely into each other’s eyes and maintain eye contact throughout the interaction. Sometimes, females grimace or “grin” by baring their teeth wide and also utter screams or squeals that are thought to be associated with sexual climax. The Bonobo’s clitoris is prominent and well-developed; during sexual arousal it undergoes a full erection of both the shaft and glans (in humans, only the glans of the clitoris becomes enlarged), swelling to nearly twice its regular size. Remarkably, clitoral penetration has occasionally been observed between females during homosexual interactions (in captivity). When penetration occurs, the females often switch to vertical thrusting (as in heterosexual mating) rather than the usual sideways hip movements.

Genital stimulation between females is sometimes performed in different positions: the two partners may both hang from a branch facing each other; one female may mount the other from behind; one female might lie on her back while the other stands facing away from her, rubbing her genitals on her recumbent partner’s vulva; or both females may lie on their backs or stand rump-to-rump while GG-rubbing. In the face-to-face position, females may alternate between who is on bottom and who is on top; prior to interacting, they often “negotiate” positions by lying down with legs spread to see whether the other partner wants to be on top. GG-rubbing occurs among females of all ages, from adolescent to very old, but if an older and a younger female are interacting, often the younger female will be on top. Sexual activity may also be more common when the females are of different ranks. Homosexual interactions are often initiated with a characteristic series of “courtship” signals: approaching the partner and peering closely, standing on the hind legs and raising the arms over the head while making eye contact, and/or touching the shoulder or knee while staring. Among captive Bonobos, partners may also use a highly developed “lexicon” of manual gestures to help negotiate the position(s) to be used in sexual interactions (see pp. 66–69 for more detailed discussion).

Females may have multiple sexual partners. In one troop containing ten females, each female interacted sexually with five other females on average, and some had as many as nine different partners. Group sexual activity also occasionally takes place, with three to five females simultaneously rubbing their genitals together. Some females are considered especially “attractive”—usually because of the shape, size, and coloration of their genital swellings—and individuals may have preferred partners that they tend to interact with more often. In fact, females typically form strongly bonded, enduring relationships with one another that are fostered by sexual interactions and include such activities as mutual grooming, play, food-sharing, and alliance-formation (often for challenging males). Females generally prefer each other’s company, and their same-sex bonds form the core of social organization. In addition, when new females (usually adolescents) join a troop, they often pair up with an older female with whom they have most of their sexual and affectionate interactions. These bonds need not be exclusive—either party may have sex with other females or males—but such mentorlike pairings can last for a year or more until the newcomer is fully integrated into the troop. In this species, a sort of homosexual “incest taboo” is in effect for these pair-bonds: most females are unrelated to the Bonobos in their new troop, but those who are related are not chosen as special partners. Some homosexual activity does, however, occur between mothers and their daughters.

Male Bonobos also have a wide variety of homosexual interactions. Sometimes, two males mutually stimulate each other’s genitals using a face-to-face position similar to GG-rubbing: one male lies on his back and spreads his legs while the other thrusts on him, rubbing their erections together (in this and all other male homosexual activity, anal penetration is not involved). If there is an age difference between partners, often the younger male will be on the bottom. Occasionally, two males hang from a branch facing each other and engage in what is known as PENIS FENCING, swinging their hips from side to side as they rub their erect penises on each other or cross them as if they were fencing with swords. Another activity is RUMP RUBBING, in which two males stand on all fours in opposite directions, pressing their buttocks against each other and mutually rubbing their anal and scrotal regions. Both males often have erections. Males also mount each other from behind and either mountee or mounter may make thrusting movements. Sometimes the males switch positions, and the mounter may scream or grin in sexual arousal as in lesbian or heterosexual interactions. Bonobo males have also been seen standing on their hind legs, one embracing the other from behind. Other sexual activities include oral sex, or fellatio, in which one male sucks another’s penis at the initiation of either partner (usually seen only in younger males). Manual stimulation of the genitals by a partner also occurs: typically an adolescent male spreads his legs and presents his erect penis to an adult male, who takes the shaft in his hand and caresses it with up-and-down movements. Younger males (and occasionally females) also sometimes give each other openmouthed kisses, often with extensive mutual tongue stimulation. Although males do not appear to form pairlike bonds with sexual partners (as do some females), occasionally two or three males are intimately associated as companions, constantly accompanying each other and foraging together.

Frequency: Homosexual activity is nearly as common as heterosexual activity in Bonobos, accounting for 40–50 percent of all sexual interactions; two-thirds to three-quarters of this same-sex activity is between females (mostly GG-rubbing). Daily life among Bonobos is characterized by numerous relatively brief episodes of sexual activity scattered throughout the day, and homosexual interactions are frequent. Each female participates in GG-rubbing on average once every two hours or so, and some newcomers to a troop do so even more often, on an hourly basis.

Orientation: Virtually all Bonobos are bisexual, interacting sexually with both males and females. In fact, motherhood and homosexual activity are fully integrated among Bonobos, as a female often GG-rubs with another female while her infant is clinging to her belly. Usually same-sex and opposite-sex activities are interspersed or alternated, although both may occur simultaneously during group sexual interactions. Nevertheless, it appears that—among some females at least—homosexual activity is preferred. Although females vary along a continuum, with one-third to nearly 90 percent of their interactions being with partners of the same sex, overall there is often a predominance of homosexual activity. An average of two-thirds of all sexual interactions among females are with other females, and individuals generally have more female than male sexual partners. In addition, females have sometimes been observed consistently ignoring males who are soliciting them for sex, preferring instead to GG-rub with each other.

Variety, flexibility, and frequency of sexual interactions are not limited to contact between Bonobos of the same sex—heterosexual activity is replete with nonreproductive behaviors. Rump rubbing, fellatio, and manual stimulation of the genitals by either sex (including fondling of the scrotum) are all aspects of male-female sexual interactions. In addition, females occasionally mount males from behind (REVERSE mounts), and heterosexual copulation often does not involve penetration and/or ejaculation, but simply mutual rubbing of genitals. Both male and female Bonobos also masturbate (males sometimes using inanimate objects to stimulate themselves). Group sexual activity occurs as well, often with one individual thrusting against a pair who are copulating, and individuals may participate in several bouts of heterosexual activity in rapid succession. Sometimes, because of the frequency and persistence of sexual invitations—often associated with begging for food—individuals (especially males) may even become annoyed and try to avoid further heterosexual interaction. In addition, females occasionally cooperate with one another in harassing and attacking males, in some cases causing severe injuries by holding a male down and biting his ears, fingers, toes, or genitals.

Bonobos mate during all phases of a female’s sexual cycle, and about a third of copulations occur during periods when fertilization is unlikely or impossible. Mating also takes place during pregnancy, sometimes as late as one month before delivery. Both adult males and females interact sexually with adolescents and juveniles (three-to-nine-year-olds). In fact, young females go through a five-to-six-year period sometimes referred to as ADOLESCENT STERILITY (although no pathology is involved) during which they actively participate in heterosexual mating (often with adults) but never get pregnant. Sexual behavior between adults and infants of both sexes is also common—about a third of the time it is initiated by the infant and may involve genital rubbing and full copulatory postures (including penetration of an adult female by a male infant). Another form of nonreproductive sexuality involves contact with other species: younger male Bonobos have occasionally been observed engaging in playful sexual interactions with redtail monkeys (Cercopithecus ascanius) in the wild.

*asterisked references discuss homosexualityltransgender

*Blount, B. G. (1990) “Issues in Bonobo (Pan paniscus) Sexual Behavior.” American Anthropologist 92: 702–14.

*Enomoto, T. (1990) “Social Play and Sexual Behavior of the Bonobo (Pan paniscus) With Special Reference to Flexibility.” Primates 31:469–80.

*Furuichi, T. (1989) “Social Interactions and the Life History of Female Pan paniscus in Wamba, Zaire.” International Journal of Primatology 10:173–97.

*Hashimoto, C. (1997) “Context and Development of Sexual Behavior of Wild Bonobos (Pan paniscus) at Wamba, Zaire.” International Journal of Primatology 18:1–21.

*Hashimoto, C., T. Furuichi, and O. Takenaka (1996) “Matrilineal Kin Relationships and Social Behavior of Wild Bonobos (Pan paniscus): Sequencing the D-loop Region of Mitochondrial DNA.” Primates 37:305–18.

*Hohmann, G. and B. Fruth (1997) “The Function of Genito-Genital Contacts among Female Bonobos (Pan paniscus).” In M. Taborsky and B. Taborsky, eds., Contributions to the XXV International Ethological Conference, p. 112. Advances in Ethology no. 32. Berlin: Blackwell Wissenschafts-Verlag.

*Idani, G. (1991) “Social Relationships Between Immigrant and Resident Bonobo (Pan paniscus) Females at Wamba.” Folia Primatologica 57:83–95.

*Kano, T. (1992) The Last Ape: Pygmy Chimpanzee Behavior and Ecology. Stanford: Stanford University Press. Translated from the Japanese by Evelyn Ono Vineberg.

*———(1990) “The Bonobos’ Peaceable Kingdom.” Natural History 99(11):62–71.

*———(1989) “The Sexual Behavior of Pygmy Chimpanzees.” In P. G. Heltne and L. A. Marquardt, eds., Understanding Chimpanzees, pp.176–83. Cambridge, Mass.: Harvard University Press.

*———(1980) “Social Behavior of Wild Pygmy Chimpanzees (Pan paniscus) of Wamba: A Preliminary Report.” Journal of Human Evolution 9:243–60.

*Kitamura, K. (1989) “Genito-Genital Contacts in the Pygmy Chimpanzee (Pan paniscus).” African Study Monographs 10:49–67.

*Kuroda, S. (1984) “Interactions Over Food Among Pygmy Chimpanzees.” In R. L. Susman, ed., The Pygmy Chimpanzee: Evolutionary Biology and Behavior, pp. 301–24. New York: Plenum Press.

*———(1980) “Social Behavior of Pygmy Chimpanzees.” Primates 21:181–97.

*Parish, A. R. (1996) “Female Relationships in Bonobos (Pan paniscus): Evidence for Bonding, Cooperation, and Female Dominance in a Male-Philopatric Species.” Human Nature 7:61–96.

*———(1994) “Sex and Food Control in the ‘Uncommon Chimpanzee’: How Bonobo Females Overcome a Phylogenetic Legacy of Male Dominance.” Ethology and Sociobiology 15:157–79.

*Roth, R. R. (1995) “A Study of Gestural Communication During Sexual Behavior in Bonobos (Pan paniscus Schwartz)”. Master’s thesis, University of Calgary.

Sabater Pi, J., M. Bermejo, G. Illera, and J. J. Vea (1993) “Behavior of Bonobos (Pan paniscus) Following Their Capture of Monkeys in Zaire.” International Journal of Primatology 14:797–804.

*Savage, S. and R. Bakeman (1978) “Sexual Morphology and Behavior in Pan paniscus.” In D. J. Chivers and J. Herbert, eds., Recent Advances in Primatology, vol. 1 , pp. 613–16. New York: Academic Press.

*Savage-Rumbaugh, E. S., and R. Lewin (1994) Kanzi: The Ape at the Brink of the Human Mind. New York: John Wiley & Sons.

*Savage-Rumbaugh, E. S., and B. J. Wilkerson (1978) “Socio-sexual Behavior in Pan paniscus and Pan troglodytes. A Comparative Study.” Journal of Human Evolution 7:327—44.

*Savage-Rumbaugh, E. S., B. J. Wilkerson and R. Bakeman (1977) “Spontaneous Gestural Communication among Conspecifics in the Pygmy Chimpanzee (Pan paniscus).” In G. Bourne, ed., Progress in Ape Research, pp. 97–116. New York: Academic Press.

*Takahata, Y, H. Ihobe, and G. Idani (1996) “Comparing Copulations of Chimpanzees and Bonobos: Do Females Exhibit Proceptivity or Receptivity?.” In W. C. McGrew, L. F. Marchant, and T. Nishida, eds., Great Ape Societies, pp. 146–55. Cambridge: Cambridge University Press.

Takeshita, H., and V. Walraven (1996) “A Comparative Study of the Variety and Complexity of Object Manipulation in Captive Chimpanzees (Pan troglodytes) and Bonobos (Pan paniscus).” Primates 37: 423-41.

*Thompson-Handler, N., R. K. Malenky, and N. Badrian (1984) “Sexual Behavior of Pan paniscus Under Natural Conditions in the Lomako Forest, Equateur, Zaire.” In R.L. Susman, ed., The Pygmy Chimpanzee: Evolutionary Biology and Behavior, pp. 347–68. New York: Plenum Press.

*de Waal, F. B. M. (1997) Bonobo: The Forgotten Ape. Berkeley: University of California Press.

*———(1995) “Sex as an Alternative to Aggression in the Bonobo.” In P. A. Abramson and S. D. Pinkerton, eds., Sexual Nature, Sexual Culture, pp. 37–56. Chicago: University of Chicago Press.

*———(1989a) Peacemaking Among Primates. Cambridge, Mass.: Harvard University Press.

*———(1989b) “Behavioral Contrasts Between Bonobo and Chimpanzee.” In P. G. Heltne and L. A. Marquardt, eds., Understanding Chimpanzees, pp. 154-73. Cambridge, Mass.: Harvard University Press.

*———(1988) “The Communicative Repertoire of Captive Bonobos (Pan paniscus), Compared to That of Chimpanzees.” Behavior 106:184–251.

*———(1987) “Tension Regulation and Nonreproductive Functions of Sex in Captive Bonobos (Pan paniscus).” National Geographic Research 3:318–35.

Walraven, V., L. Van Elsacker, and R. F. Verheyen (1993) “Spontaneous Object Manipulation in Captive Bonobos.” In L. Van Elsacker, ed., Bonobo Tidings: Jubilee Volume on the Occasion of the 150th Anniversary of the Royal Zoological Society of Antwerp, pp. 25–34. Leuven: Ceuterick Leuven.

*White, F., and N. Thompson-Handler (1989) “Social and Ecological Correlates of Homosexual Behavior in Wild Pygmy Chimpanzees, Pan paniscus.” American Journal of Primatology 18:170.

Common Chimpanzees live in groups or communities of 40–60 individuals, usually with twice as many adult females as males. Within each group, smaller subgroups often form, and some individuals form longer-lasting bonds with each other as part of a complex network of social and communicative interactions. The mating system is promiscuous or polygamous: males and females each mate with multiple partners, and males do not generally participate in raising their own offspring.

Behavioral Expression: Female Common Chimpanzees participate in a variety of same-sex activities. One form of mutual genital stimulation is sometimes known as BUMPRUMP: two females, standing on all fours and facing in opposite directions, rub their rumps together (usually in an up-and-down motion), stimulating their genital and anal regions. Sometimes one female lies on top of the other in a face-to-face position—or the two sit facing one another—rubbing their genitals together. Mounting also occurs in the front-to-back position typical of heterosexual mating. Unlike male-female mountings, though, the angle and position of the mounting female’s body and arms may be slightly different from that of a male, her pelvic thrusts may be slower or more perfunctory, and she may rub against the other female’s genitals with her belly rather than her own genital region. Occasionally female Chimps also engage in cunnilingus: one individual presents her buttocks by crouching in front of the other, who stimulates her external genitalia with her lips and tongue.

Among males, several different kinds of same-sex interactions occur. Manual contact or stimulation of a partner’s genitals, for example, can involve fondling, rubbing, or gripping of the penis and/or touching of the scrotum, sometimes while the partner makes pelvic thrusts that “bounce” his genitals on his partner’s hand. Chimps occasionally also engage in fellatio, mutual penis-rubbing while sitting face-to-face, mounting in a front-to-back position (sometimes with pelvic thrusts or body shaking), and even insertion of a finger into the partner’s anus and oralanal “grooming” in a 69 position. A number of these activities—notably genital touching, mounting, and anal contact—occur as ritualized sexual gestures in the context of greeting, enlisting of support, reconciliation, and/or reassurance. They are often combined with affectionate gestures between males such as embracing, kissing (including openmouthed contact), grooming, and genital kissing or nuzzling. Males who participate in such activities may be bonded together in a mutually supportive “friendship” or COALITION. Occasionally male Chimpanzees also interact sexually with male Savanna Baboons in the wild. One adolescent Chimp, for example, was observed holding and fondling the penis of an adult male Baboon.

Transgendered or intersexual Common Chimpanzees occasionally occur as well. One individual who was physically and anatomically a male was chromosomally a mosaic, combining both the male (XY) and the female (XX) chromosome types.

Frequency: The prevalence of same-sex activities between male Common Chimpanzees is highly variable. Mounting between males constitutes anywhere from 1–2 percent to one-third or one-half of the behaviors involved in reassurance, enlistment of support, and other activities during or following conflicts. Kissing and embracing between males constitute from 12–30 percent of such interactions (depending on the population). Overall, 29–33 percent of all mounting activity occurs between males. Less detailed information is available for females, but a similar range of frequencies is probably involved. Other homosexual activities such as bumprump and oral or manual stimulation of genitals have so far been observed largely in captivity, where they may be fairly common.

Orientation: Most adult male Chimpanzees that participate in same-sex mounting, genital handling, or other activities also mate with females. Younger (adolescent or juvenile) males, who occasionally engage in such activities as fellatio or mutual genital rubbing, may be less heterosexually involved. In some populations, virtually all adult males participate in same-sex mounting, although such behavior may constitute anywhere from one-fifth to three-quarters of an individual’s mounting activity. Females that participate in same-sex activities are also usually functionally bisexual, copulating with males as well. However, a few individuals appear to be more exclusively homosexual: one female, for example, refused to mate with males and was only involved sexually with other females for many years. She even developed a close relationship with another female and her offspring. Socially, she occupied an intermediate position between the male and female subgroups: she often associated with males and “ganged up” with them against other individuals, but she also maintained primary bonds with females and sometimes even defended them against the sexual advances of males. Later, however, she also mated with males.

Common Chimpanzees engage in a variety of nonprocreative heterosexual practices that parallel their same-sex behaviors. Heterosexual oral sex involves both cunnilingus (males licking the vagina or mouthing the labia) and fellatio (females sucking or nuzzling the penis). Manual stimulation of the genitals also occurs: males sometimes insert a finger into the vagina (the female may then move his hand in order to stimulate herself), while females occasionally fondle their partner’s penis. In addition, bumprump takes place between males and females (sometimes including thrusting and scrotum handling), and both sexes masturbate—stimulating their own genitals manually or with various implements. Some males even perform AUTO-FELLATIO, i.e., they suck their own penis. Male Chimpanzees occasionally mount females without achieving penetration or ejaculate after withdrawing; they may also mate with females who are not in heat. Another form of nonprocreative sex is copulation during pregnancy: some females participate in heterosexual activity for 75–80 percent of the time that they are pregnant. In addition, male Chimps have been observed copulating with female Savanna Baboons in the wild.

When females are in heat, they typically mate numerous times and with multiple partners—as often as six or more times a day (sometimes with two to seven males in quick succession), for a total of several hundred times for each baby conceived. In some cases, though, heterosexual relations are less than amicable: males occasionally try to force females to consort and mate with them by threatening and even violently attacking them, and females often display “blunt refusal” or “abhorrence” reactions toward the advances of older males. Copulations are often interrupted or harassed by other Chimps trying to disrupt the sexual activities. In addition, infanticide and even cannibalism occasionally occur. For example, infants conceived outside the community may be killed by the resident males, and most females mate with males belonging to their own social group. However, in some populations a considerable number of females seek partners outside their group, engaging in “furtive” matings with them. In one community, for example, more than half of all offspring were sired by males living in other groups.

Although incestuous matings between adults are not common, mothers engage in sexual activity with their infant sons fairly often. Young females typically experience a one-to-three-year period of ADOLESCENT STERILITY after their first menstruation, during which time they mate heterosexually without conceiving. Some adult females practice a unique form of birth control: they simulate the contraceptive effect of nursing by stimulating their own nipples, in some cases preventing pregnancy for up to ten years. Females may also experience a postreproductive or “menopausal” period later in their lives, lasting up to two years (about 4–5 percent of the maximum life span). During this time they often continue to mate, accounting for up to 20 percent of all female sexual activity in a group.

*asterisked references discuss homosexuality/transgender

*Adang, O. M. J., J. A. B. Wensing, and J. A. R. A. M. van Hooff (1987) “The Arnhem Zoo Colony of Chimpanzees Pan troglodytes: Development and Management Techniques.” International Zoo Yearbook 26:236–48.

*Bingham, H. C. (1928) “Sex Development in Apes.” Comparative Psychology Monographs 5:1–165.

Bygott, J. D. (1979) “Agonistic Behavior, Dominance, and Social Structure in Wild Chimpanzees of the Gombe National Park.” In D. A. Hamburg and E. R. McCown, eds., The Great Apes, pp. 405-28. Menlo Park, Calif.: Benjamin Cummings.

*———(1974) “Agonistic Behavior and Dominance in Wild Chimpanzees.” Ph.D. thesis, Cambridge University.

Dahl, J. F., K. J. Lauterbach, and C. A. Duffey (1996) “Birth Control in Female Chimpanzees: Self-Directed Behaviors and Infant-Mother Interactions.” American Journal of Physical Anthropology supp. 22:93.

*Egozcue, J. (1972) “Chromosomal Abnormalities in Primates.” In E. 1. Goldsmith and J. Moor-Jankowski, eds., Medical Primatology 1972, part I, pp. 336–41. Basel: S. Karger.

Gagneux, P. , D. S. Woodruff, and C. Boesch (1997) “Furtive Mating in Female Chimpanzees.” Nature 387:358–59.

*Goodall, J. (1986) The Chimpanzees of Gombe: Patterns of Behavior. Cambridge, Mass.: Belknap Press.

(1977) “Infant Killing and Cannibalism in Free Living Chimpanzees.” Folia Primatologica 28:259–82.

*———(1965) “Chimpanzees of the Gombe Stream Reserve.” In 1. deVore, ed., Primate Behavior: Field Studies of Monkeys and Apes, pp. 425–73. New York: Holt, Rinehart & Winston.

*Köhler, W. (1925) The Mentality of Apes. London: Routledge & Kegan Paul.

*Kollar, E. J., W. C. Beckwith, and R. B. Edgerton (1968) “Sexual Behavior of the ARL Colony Chimpanzees.” Journal of Nervous and Mental Disease 147:444–59.

*Kollar, E. J., R. B. Edgerton, and W. C. Beckwith (1968) “An Evaluation of the Behavior of the ARL Colony Chimpanzees.” Archives of General Psychiatry 19:580-94.

*Kortlandt, A. (1962) “Chimpanzees in the Wild.” Scientific American 206(5):128-38.

*Lawick-Goodall, J. van (1968) “The Behavior of Free-Living Chimpanzees in the Gombe Stream Reserve.” Animal Behavior Monographs 1:161–311.

*Nishida, T. (1997) “Sexual Behavior of Adult Male Chimpanzees of the Mahale Mountains National Park, Tanzania.” Primates 38:379–98.

———(1990) The Chimpanzees of the Mahale Mountains: Sexual and Life History Strategies. Tokyo: University of Tokyo Press.

———(1979) “The Social Structure of Chimpanzees of the Mahale Mountains.” In D. A. Hamburg and E. R. McCown, eds., The Great Apes, pp. 73–121. Menlo Park, Calif.: Benjamin Cummings.

*———(1970) “Social Behavior and Relationship Among Wild Chimpanzees of the Mahali Mountains.” Primates 11:47–87.

*Nishida, T., and K. Hosaka (1996) “Coalition Strategies Among Adult Male Chimpanzees of the Mahale Mountains, Tanzania.” In W. C. McGrew, L. F. Marchant, and T. Nishida, eds., Great Ape Societies, pp. 114–34. Cambridge: Cambridge University Press.

*Reynolds, V., and F. Reynolds (1965) “Chimpanzees of the Budongo Forest.” In 1. deVore, ed., Primate Behavior: Field Studies of Monkeys and Apes, pp. 368–424. New York: Holt, Rinehart & Winston.

Takahata, Y., N. Koyama, and S. Suzuki (1995) “Do the Old Aged Females Experience a Long Postreproductive Life Span?: The Cases of Japanese Macaques and Chimpanzees.” Primates 36:169–80.

Tutin, C. E. G., and P. R. McGinnis (1981) “Chimpanzee Reproduction in the Wild.” In C.E. Graham, ed., Reproductive Biology of the Great Apes, pp. 239–64. New York: Academic Press.

*Tutin, C. E. G., and W. C. McGrew (1973a) “Chimpanzee Copulatory Behavior.” Folia Primatologica 19:237–56.

———(1973b) “Sexual Behavior of Group-Living Adolescent Chimpanzees.” American Journal of Physical Anthropology 38:195–200.

*de Waal, F. B. M. (1982) Chimpanzee Politics: Power and Sex Among Apes. New York: Harper & Row.

*de Waal, F. B. M., and J. A. R. A. M. van Hooff (1981) “Side-directed Communication and Agonistic Interactions in Chimpanzees.” Behavior 77:164–98.

Wrangham, R. W. (1997) “Subtle, Secret Female Chimpanzees.” Science 277:774–75.

*Yerkes, R. M. (1939) “Social Dominance and Sexual Status in the Chimpanzee.” Quarterly Review of Biology 14:115-36.

Gorillas live in small groups of eight to fifteen individuals, usually consisting of three to six adult females, one mature male, one to two juvenile males, and five to seven immature offspring. All-male groups also regularly occur. The mating system is polygynous, i.e., the mature male mates with all of the females in the group. The females are usually not related to each other, since they generally leave their family group once reaching adulthood—in many other group-living primates, males leave a core group of (usually related) females.

Behavioral Expression: Within her group, a female Gorilla sometimes forms an intense pairlike friendship with another female, spending as much time with her as with the breeding male of the group. Her interactions with this “favorite” female consist of constant touching while they spend time together, sitting with each other or lying one against the other, and frequent mutual grooming. Female Gorillas also frequently have sex with other females in their group. In a typical lesbian interaction, one female approaches another directly, often making copulatory vocalizations, after which they may sit quietly together for a while. Often they will begin to fondle each other’s genitals or bring their face into intimate contact with the other’s vulva, smelling or touching with their mouths. This is usually followed by embracing in a face-to-face position (usually lying down) with rubbing of the genitals against each other, sometimes accompanied by growling, grunting, screaming, or pulsing whimpers. The animals may also pause during periods of pelvic thrusting to caress each other, shift their positions, or masturbate themselves.

Lesbian sexual activity is notable for its differences from heterosexual copulation, probably related to an emphasis on achieving mutual pleasure. First of all, the more intimate face-to-face position is rarely used between males and females, who instead mate with the male mounting from behind (and often with the male thrusting and vocalizing significantly less than his partner). Sexual interactions between females are also generally more affectionate, involving much more embracing and grooming, and they usually last longer. One study revealed that sexual interactions between females last on average five times longer than heterosexual ones, and that lesbian activity involves considerably more thrusting and genital stimulation.

Female Gorillas also exhibit clear preferences for particular female sexual partners within their group. Although lesbian activity generally occurs among all members of a group, each female usually has a favorite partner with whom she interacts more often. Homosexuality is also integrated into the general reproductive cycle of the group: breeding females (including mothers) have sex with other females as much as do nonbreeding females, and lesbian sex is common even during pregnancy, sometimes as late as a week or two before birth.

Although male Gorillas (especially younger animals) sometimes mount each other in cosexual groups, homosexuality occurs most commonly in all-male groups, where probably more than 90 percent of all same-sex activity between males takes place. Such groups result when females leave their home group to join another, or when males occasionally leave their own group upon reaching maturity and band together. All-male groups persist for many years and have a complex network of homosexual pairings. Each male has preferred partners whom he courts and has sex with; some interact with only one other male in the group, while others have multiple partners (up to five have been recorded for one individual). Durations of individual pairings can be anywhere from a few months to a year or more. Participants are sometimes related to each other: in one all-male group, about 40 percent of all homosexual activity occurred between half brothers. There is often intense competition among the males for “preferred” partners—often the younger males—and older, higher-ranking males frequently “guard” their favorite males and fight to protect them from the advances of other males. Nevertheless, rates of aggression are significantly lower in all-male groups than in cosexual groups, and some male groups exhibit a high degree of cohesiveness attributable to the sexual bonding and mediating activities of their members.

When one male Gorilla is courting another, he approaches while making intense panting sounds; sometimes contact is initiated with one (or both) males reaching out to touch the other, or one may make a more subtle soliciting approach. Sexual activity involves one male mounting another and thrusting, in either the face-to-face or front-to-back position; both males often emit grumbling, growling, or panting sounds. Orgasm is signaled when the animal emits a deep sigh on dismounting, and often there is direct evidence of ejaculation (e.g., semen spilled on his partner). Most males both mount and are mounted, except for the oldest silverback males, who only mount. Like lesbian interactions, male homosexual encounters tend to last, on average, longer than heterosexual ones and to use the face-to-face position more often than in male-female interactions (though less often than between females). Male Gorillas also touch and fondle each other’s genitals in addition to mounting one another.

Frequency: In cosexual groups, 9 percent of all sexual activity is lesbian and 58 percent of all social/affectionate interactions of females are with other females (mostly with their “favorite” partner); about 2 percent of mounting episodes occur between adult males in such groups. Among younger animals (e.g., adolescents and juveniles) in cosexual groups, 7–36 percent of mounts are between males and 9–14 percent between females. Male homosexual courtship and copulation occur daily in some all-male groups and are thought to exceed the amount of heterosexual activity that takes place in cosexual groups. Some males may engage in homosexual copulation more than 75 times a year in such groups, and homosexual courtship, at its peak, can take place as often as 7 times an hour. Up to 10 percent of groups in some populations are all-male, and Gorillas spend an average of six years in such groups, with some males staying ten or more years (and even occasionally remaining until their death).

Orientation: Many female Gorillas are bisexual, having sexual and affectionate relationships with both males and females, but there are clear differences in the extent to which various individuals participate in homosexual versus heterosexual activity. In general, it appears that a continuum exists from those females who prefer lesbian activity (they account for a large proportion of the same-sex interactions), to those who have a fairly equal amount of interaction with both males and females, to those who interact primarily with males. Many male Gorillas are probably sequentially bisexual, spending portions of their lives having only homosexual encounters (in all-male groups), followed by periods of only heterosexual interactions, and so on. Other males, especially younger ones, may be simultaneously bisexual. Depending on the circumstances (such as the particular group composition), some males may also have primarily or exclusively homosexual interactions throughout their lives, while others may have only heterosexual ones, but it appears that all males at least have the capacity for bisexuality.

As noted above, sex (both heterosexual and homosexual) during pregnancy is common among Gorillas. Both males and females also engage in masturbation, and younger animals frequently participate in nonpenetrative sexual activity. Mountings of the latter type are usually incestuous, involving siblings, half siblings, or (more rarely) parents and their offspring (or their siblings’ offspring). In captivity, oral sex and manual stimulation of genitals have also been observed in heterosexual interactions. Male Gorillas generally appear to have less interest in sex than females and are sometimes rather reluctant or perfunctory participants in mating. Heterosexual interactions are nearly always initiated by females (whose advances are often initially ignored by the males), males often thrust and vocalize much less than females during copulation (often for no more than 20 seconds), and females generally determine when a particular sexual interaction is finished. However, females may be sexually inactive for up to three or four years while nursing their young. Infanticide is quite common among wild Gorillas: more than 40 percent of all infant deaths in one population were due to infanticide, usually by an adult male trying to gain breeding access to a female (although females have been known to kill infants as well). Probably all adult males commit infanticide at least once during their lifetime, while most females are likely to lose at least one infant during their lifetime to killing by another of their own species.

*asterisked references discuss homosexuality/transgender

*Coffin, R. (1978) “Sexual Behavior in a Group of Captive Young Gorillas.” Boletin de Estudios Medicos y Bi-ológicos 30:65-69.

*Fischer, R. B. and R.D. Nadler (1978) “Affiliative, Playful, and Homosexual Interactions of Adult Female Lowland Gorillas.” Primates 19:657-64.

*Fossey, D. (1990) “New Observations of Gorillas in the Wild.” In Grzimek’s Encyclopedia of Mammals, vol. 2, pp. 449-62. New York: McGraw-Hill.

(1984) “Infanticide in Mountain Gorillas (Gorilla gorilla beringei) with Comparative Notes on Chimpanzees.” In G. Hausfater and S. B. Hrdy, eds., Infanticide: Comparative and Evolutionary Perspectives, pp. 217–35. New York: Aldine.

*———(1983) Gorillas in the Mist. Boston: Houghton Mifflin.

*Harcourt, A. H. (1988) “Bachelor Groups of Gorillas in Captivity: The Situation in the Wild.” Dodo 25:54-61.

*———(1979a) “Social Relations Among Adult Female Mountain Gorillas.” Animal Behavior 27:251-64.

————(1979b) “Social Relationships Between Adult Male and Female Mountain Gorillas in the Wild.” Animal Behavior 27:325-42.

*Harcourt, A. H., D. Fossey, K. J. Stewart, and D. P. Watts (1980) “Reproduction in Wild Gorillas and Some Comparisons with Chimpanzees.” Journal of Reproduction and Fertility suppl. 28:59–70.

Harcourt, A. H., and K. J. Stewart (1978) “Sexual Behavior of Wild Mountain Gorillas.” In D. J. Chivers and J. Herbert, eds., Recent Advances in Primatology, vol. 1, pp. 611-12. New York: Academic Press.

*Harcourt, A. H., K. J. Stewart, and D. Fossey (1981) “Gorilla Reproduction in the Wild.” In C. E. Graham, ed., Reproductive Biology of the Great Apes, pp. 265-79. New York: Academic Press.

*Hess, J. P. (1973) “Some Observations on the Sexual Behavior of Captive Lowland Gorillas, Gorilla g. gorilla (Savage and Wyman).” In R. P. Michael and J. H. Crook, eds., Comparative Ecology and Behavior of Primates, pp. 507-81. London: Academic Press.

*Nadler, R. D. (1986) “Sex-Related Behavior of Immature Wild Mountain Gorillas.” Developmental Psychobiology 19:125-37.

*Porton, I., and M. White (1996) “Managing an All-Male Group of Gorillas: Eight Years of Experience at the St. Louis Zoological Park.” In AAZPA Regional Conference Proceedings, pp. 720-28. Wheeling, W.V.: American Association of Zoological Parks and Aquariums.

*Robbins, M. M. (1996) “Male-Male Interactions in Heterosexual and All-Male Wild Mountain Gorilla Groups.” Ethology 102:942-65.

*———(1995) “A Demographic Analysis of Male Life History and Social Structure of Mountain Gorillas.” Behavior 132:21-47.

*Schaller, G. (1963) The Mountain Gorilla. Chicago: University of Chicago Press.

*Stewart, K. J. (1977) “Birth of a Wild Mountain Gorilla (Gorilla gorilla beringei).” Primates 18:965-76.

Watts, D. P. (1990) “Mountain Gorilla Life Histories, Reproductive Competition, and Sociosexual Behavior and Some Implications for Captive Husbandry.” Zoo Biology 9:185-200.

———(1989) “Infanticide in Mountain Gorillas: New Cases and a Reconsideration of the Evidence.” Ethology 81:1-18.

*Yamagiwa, J. (1987a) “Intra- and Inter-Group Interactions of an All-Male Group of Virunga Mountain Gorillas (Gorilla gorilla beringei).” Primates 28:1-30.

*———(1987b) “Male Life History and the Social Structure of Wild Mountain Gorillas (Gorilla gorilla beringei).” In S. Kawano, J. H. Connell, and T. Hidaka, eds., Evolution and Coadaptation in Biotic Communities, pp. 31-51. Tokyo: University of Tokyo Press.

Adult Orang-utans are largely solitary—males and females live separate from each other and interact only when the female is ready to mate. Younger Orangs, however, are more sociable and may actively seek each other’s company and interact in groups. The mating system is polygynous: males copulate with multiple females and no long-lasting heterosexual pairing occurs, although males and females may “consort” together for shorter periods during mating. Males do not participate in parenting.

Behavioral Expression: Orang-utans engage in a variety of homosexual activities, including a range of different sexual techniques and various affectionate and pairing behaviors. Mounting among male Orangs, especially younger adults (10-15 years old) and adolescents (7-10 years old) often develops into full anal intercourse, with erection of the penis, pelvic thrusting, penetration, and ejaculation. In a more unusual type of homosexual penetration, a male sometimes tries to insert his penis into the small hollow formed when his partner’s penis retracts. Another prominent homosexual activity is fellatio (oral-genital contact): one male will lick and suck another’s erect penis. In some cases, males take turns fellating each other. Males occasionally also fondle and touch the erect penis of another male, often examining the organ closely by parting the hairs in the genital region. Lesbian activity in Orangs usually involves one female fondling the genitals of another female, often inserting her fingers (thumb or other digits) into the vagina of the other. Sometimes she also masturbates herself with her foot while she is penetrating the other female. Mounting rarely, if ever, occurs among female Orangs, unlike in many other animals in which females engage in homosexual behavior. Female homosexual encounters may last for up to 12 minutes, comparable to the 10-15 minute duration of most heterosexual copulations. Although Orang-utans are usually willing participants in homosexual encounters, sometimes one animal is more reluctant and the partner will then attempt to restrain him or her, for example by using the feet to hold him or her down. However, this contrasts sharply with heterosexual encounters, in which females often scream and struggle violently while males attempt to forcibly mate with them (see the discussion on heterosexualities below).

Sexual behavior often occurs within a “bonding” or special friendship-like pairing between younger animals of the same sex. Two males or two females may become quite attached, following one another over several days, playing together (including play-wrestling), sharing food, and generally spending a great deal of time together and coordinating their activities. One partner may even throw a “temper tantrum” when the other ventures too far away or fails to wait for its companion. Female Orangs have also been known to compete with males for sexual access to a favorite female partner with whom they later develop a bonded relationship. Same-sex companions demonstrate a number of affectionate behaviors toward each other—females, for example, may embrace, cling to one other, walk in tandem, or groom each other, and males may “kiss” each other. While in some cases this mouth-to-mouth contact may be for the exchange of food or drink, in other cases it appears to be more of an affectionate or greeting gesture. Such companionships also develop between animals of the opposite sex, and indeed they resemble in many ways the “consortships” that sometimes characterize heterosexual mating relations. Companionships, however, need not involve any sexual contact, whether between animals of the same or opposite sex.

Homosexual interactions sometimes also occur between male Orangs and Crab-eating Macaques. These monkeys often associate with Orangs, feeding in the same areas and interacting nonaggressively. Orangs and Crab-eating Macaques may groom each other, and male Orang-utans will occasionally suck the penis of an adult male Crab-eating Macaque.

Transgendered Orang-utans occasionally occur as well: individuals have been found who are physically male yet have a female (XX) chromosome pattern.

Frequency: Approximately 9 percent of all Orang-utan sexual encounters in some populations involve males mounting each other; the proportion of same-sex activity is probably even higher, since male oral-genital contacts and female homosexual encounters are not included in this figure. Females who engage in lesbian activity may do so frequently and repeatedly over several days, similar to the repeated sexual interactions in a heterosexual consortship.

Orientation: Male homosexual behavior is characteristic of younger Orang-utans. Not all younger males engage in same-sex activity, but those who do are probably bisexual, since most such individuals are also involved in heterosexual pursuits. Mature adult males probably have a bisexual potential: although they rarely engage in homosexual activity in the wild, in captivity they often do (even in the presence of females). Female Orangs are probably also bisexual—for example, one female who was sexually active with another female later mated heterosexually and raised young. However, while engaged in homosexual behavior, she was exclusively lesbian, since she completely ignored males and focused her attentions entirely on other females.

A wide variety of nonprocreative heterosexual activities are found in Orang-utans. Both males and females often stimulate their partner’s genitals with their mouth or hands, and females may also rub their genitals against the male. The female has a prominent clitoris that is stimulated during intercourse, and she often takes the initiative in heterosexual activity, actually mounting the male, manually guiding his penis into her, and performing pelvic thrusts while he lies on his back. A variety of positions are used for heterosexual copulation, including face-to-face (the most common), front-to-back, and sideways. In almost 30 percent of mounts, vaginal penetration and/or ejaculation do not occur. Anal stimulation can be a component of heterosexual interactions as well: both males and females lick, suck, blow on, insert fingers into, and rub their genitals on their partner’s anus; males have also been known to engage in anal intercourse (penetration) with females. Females may consort and copulate with multiple male partners, and copulation can occur throughout pregnancy up to the time of birth. Masturbation is also common among Orangs—females rub their fingers or foot on their clitoris or insert a finger or toe into their vagina, while males rub their penises with their fist or foot. Both males and females also use inanimate objects or “tools” to masturbate. Males sometimes become sexually aroused and spontaneously ejaculate during long-calling (a courtship and territorial vocalization used by mature males). Mothers frequently engage in incestuous contact with their infants, manually or orally stimulating the penis or clitoris (or being stimulated by the infant), and may even mount the infants.

Heterosexual relations are sometimes characterized by aggression and violence rather than pleasure and consensuality. Younger males often chase, harass, and rape females. During such interactions, which may account for the majority of copulations in some populations, the male may grab, slap, bite, and forcibly restrain the female, who struggles violently while screaming or whimpering. Occasionally (about 7-8 percent of the time) she does manage to break free. An unusual form of reproductive suppression also occurs among male Orangs. Although they become sexually mature at seven to ten years old, males generally fail to develop the full range of secondary sexual characteristics (such as the large cheek pads or “flanges,” a throat pouch, and a general weight increase) for another seven years, and sometimes this is delayed for as long as two decades. It is thought that this development is suppressed by the presence of a mature male, perhaps through social intimidation or stress, although the exact mechanism is not known. Nonbreeding males have been found to have higher estrogen levels than breeding males, so perhaps a physiological effect is also involved. Interestingly, nonflanged younger males have been observed copulating repeatedly with females without resulting in any pregnancies; perhaps this is related to their arrested sexual development, although it is also possible that they were simply mating during the nonovulatory phase of the female’s cycle. In addition, adolescent females experience ADOLESCENT STERILITY, lasting a year or longer, during which they can copulate without becoming pregnant. In fact, adolescent females have higher copulation rates than adult females, accounting for more than 60 percent of heterosexual mating. Adult females breed relatively infrequently, perhaps once every four to eight years. Because females in some populations tend to have synchronized reproductive cycles, there may be periods of up to two years when no adult females are available for mating.

*asterisked references discuss homosexuality/transgender

*Dutrillaux, B., M.-O. Rethoré, and J. Lejeune (1975) “Comparaison du caryotype de l‘orang-outang (Pongo pygmaeus) à celui de l’homme, du chimpanzé, et du gorille [Comparison of the Karyotype of the Orang-utan to Those of Man, Chimpanzee, and Gorilla].” Annales de Génétique 18:153-61.

Galdikas, B. M. F. (1995) “Social and Reproductive Behavior of Wild Adolescent Female Orangutans.” In R. D. Nadler, B. M. F. Galdikas, L. K. Sheeran, and N. Rosen, eds., The Neglected Ape, pp. 183-90. New York: Plenum Press.

———(1985) “Orangutan Sociality at Tanjung Puting.” American Journal of Primatology 9:101-19.

———(1981) “Orangutan Reproduction in the Wild.” In C. E. Graham, ed., Reproductive Biology of the Great Apes, pp. 281-300. New York: Academic Press.

Harrisson, B. (1961) “A Study of Orang-utan Behavior in the Semi-Wild State.” International Zoo Yearbook 3:57-68.

Kaplan, G., and L. Rogers (1994) Orang-Utans in Borneo. Armidale, Australia: University of New England Press.

Kingsley, S. R. (1988) “Physiological Development of Male Orang-utans and Gorillas.” In J.H. Schwartz, ed., Orang-utan Biology, pp. 123-31. New York: Oxford University Press.

———(1982) “Causes of Nonbreeding and the Development of the Secondary Sexual Characteristics in the Male Orang Utan: A Hormonal Study.” In L. E. M. de Boer, ed., The Orang Utan: Its Biology and Conservation, pp. 215-29. The Hague: Dr W. Junk Publishers.

*MacKinnon, J. (1974) “The Behavior and Ecology of Wild Orang-utans (Pongo pygmaeus).” Animal Behavior 22:3-74.

*Maple, T. L. (1980) Orang-utan Behavior. New York: Van Nostrand Reinhold.

Mitani, J. C. (1985) “Mating Behavior of Male Orangutans in the Kutai Game Reserve, Indonesia.” Animal Behavior 33:392-402.

*Morris, D. (1964) “The Response of Animals to a Restricted Environment.” Symposia of the Zoological Society of London 13:99-118.

Nadler, R. D. (1988) “Sexual and Reproductive Behavior.” In J. H. Schwartz, ed., Orang-utan Biology, pp. 105-16. New York: Oxford University Press.

———(1982) “Reproductive Behavior and Endocrinology of Orang Utans.” In L. E. M. de Boer, ed., The Orang Utan: Its Biology and Conservation, pp. 231-48. The Hague: Dr W. Junk Publishers.

*Poole, T. B. (1987) “Social Behavior of a Group of Orangutans (Pongo pygmaeus) on an Artificial Island in Singapore Zoological Gardens.” Zoo Biology 6:315-30.

*Rijksen, H. D. (1978) A Fieldstudy on Sumatran Orang Utans (Pongo pygmaeus abelii Lesson 1827): Ecology, Behavior, and Conservation. Wageningen, Netherlands: H. Veenman & Zonen b.v.

Rodman, P. S. (1988) “Diversity and Consistency in Ecology and Behavior.” In J. H. Schwartz, ed., Orang-utan Biology, pp. 31-51. New York: Oxford University Press.

Schürmann, C. (1982) “Mating Behavior of Wild Orang Utans.” In L. E. M. de Boer, ed., The Orang Utan: Its Biology and Conservation, pp. 269-84. The Hague: Dr W. Junk Publishers.

Schürmann, C., and J. A. R. A. M. van Hooff (1986) “Reproductive Strategies of the Orang-Utan: New Data and a Reconsideration of Existing Sociosexual Models.” International Journal of Primatology 7:265-87.

*Turleau, C., J. de Grouchy, F. Chavin-Colin, J. Mortelmans, and W. Van den Bergh (1975) “Inversion péri-centrique du 3, homozygote et hétérozygote, et translation centromérique du 12 dans une famille d’orangs-outangs. Implications évolutives [Pericentric Inversion of Chromosome 3, Homozygous and Heterozygous, and Transposition of Centromere of Chromosome 12 in a Family of Orang-utans. Implications for Evolution].” Annales de Génétique 18:227-33.

Utani, S., and T. M. Setia (1995) “Behavioral Changes in Wild Male and Female Sumatran Orangutans (Pongo pygmaeus abelii) During and Following a Resident Male Take-over.” In R. D. Nadler, B.M.F. Galdikas, L.K. Sheeran, and N. Rosen, eds., The Neglected Ape, pp. 183-90. New York: Plenum Press.

Gibbons generally live in family groups consisting of a paired male and female and their offspring. Siamang heterosexual pairs may be more closely bonded than those of White-handed Gibbons. Both males and females perform complex vocal duets as part of bonding and territorial displays, although separate family groups have relatively little interaction with one another.

Behavioral Expression: Within their nuclear family groups, male Gibbons sometimes engage in homosexual activities with each other. This incestuous activity often takes place between an adolescent or younger male and his father (or stepfather, if his parents have divorced and re-paired); in Siamangs it may also occur between brothers. A typical homosexual encounter between father and son in White-handed Gibbons occurs in the trees in the morning or early afternoon, while the family is resting or feeding. The mother is generally nonchalant about such encounters, ignoring the sexual activity even if she is close at hand. The two males often groom each other or engage in playful wrestling or chasing as part of their interaction. During such activities, either male may approach the other to initiate sex, which consists primarily of the two males rubbing their erect penises together, often leading to orgasm. This is done face-to-face (unlike heterosexual copulation, which is typically performed front-to-back). The father lifts up his knees and spreads his legs wide while sitting on a branch or hanging by his arms—this is an invitation to his son to have sex. The adolescent male embraces his father around the waist with his legs, then lowers his body until he is, in effect, sitting in his father’s lap, with his legs resting on top of the older male’s thighs. This allows their genitals to come into direct contact, and the younger male usually begins rapidly thrusting against his father; sometimes the older male will make pelvic thrusts as well. If his son ejaculates on him, the father may scoop up the semen and eat it. Genital contact can last for up to a minute, although the average is about 20 seconds; in comparison, heterosexual copulations in this species average only about 15 seconds.

A similar form of genital rubbing occurs between father and son in Siamangs. While both males are hanging by their arms, the younger grasps his father around the waist with his legs and both thrust against each other (in this species, heterosexual mating is occasionally also performed face-to-face). Unlike in White-handed Gibbons, this activity is sometimes accompanied by threats between the two males, and it appears that the younger male may on occasion want to terminate the activity before his father does. Sometimes two brothers—juveniles or adolescents, four to nine years old—thrust against each other face-to-face as well. Brothers are also generally affectionate with each other, touching and grooming one another, putting their arms over each other’s shoulders, and wrestling together. Fellatio also sometimes occurs in Siamangs: usually an older brother will lick and gently nibble on the penis and groin of his younger brother (who may be only one to three years old) while the latter dangles by his arms above him or sits with his legs spread. The older male may also masturbate the younger by pulling on his erect penis; if ejaculation occurs, the semen may be eaten. Occasionally, a son will lick and groom his father’s genital area, or the father might insert one of his fingers into his son’s anus.

Frequency: In those Gibbon families where homosexual activity takes place, it occurs quite frequently, and at rates that may equal or exceed heterosexual activity. In one White-handed Gibbon family, the father and son sometimes had sexual encounters as often as 8 times a day—although they averaged about twice a day—and homosexual activity took place on more than a third of the days that the family was observed. In fact, during one 18-day period, 44 homosexual interactions were recorded. In comparison, 23 heterosexual copulations were observed in another family over 18 (different) days, at a rate of 1-3 per day; other studies have found rates of 2 heterosexual matings per day (equivalent to heterosexual activity on about a third of the observation days). In a Siamang family observed in a zoo, about 30 percent of all sexual interactions were between males. It is not yet known, however, in what proportion of families homosexual activity occurs (in either of these species).

Orientation: Male Gibbon sexual life is probably sequentially bisexual, characterized by alternating periods of heterosexual and homosexual activity, with occasional long-term exclusive homosexuality. Younger males may experience entirely homosexual interactions with their fathers, or sexual activity with both parents (see below) while they are growing up, and then go on to mate heterosexually as adults. Once paired with a female, they may engage in incestuous encounters with their offspring of both sexes or have extended periods of exclusive homosexuality. In one White-handed Gibbon family, no heterosexual interactions were observed between the father and his female mate during the entire two years that homosexual activity was taking place between him and his son.

Like many other species where homosexual activity occurs between related individuals, heterosexual incest is also prominent among Gibbons. Siamang mothers and fathers both interact sexually with their offspring of the opposite sex, as do siblings. Adult males sometimes perform copulation-like thrusting with their daughters, as well as oral and manual stimulation of their genitals. In one case, a Siamang father was observed fondling his adolescent daughter’s vulva with his fingers while her younger brother licked her clitoris. Mothers may invite their juvenile sons—as young as four to five years—to lick and groom their genitals (usually with no hostile reaction from the father). When offspring grow up, mother-son pairs (and occasionally, brother-sister pairs) may sometimes develop in both White-handed Gibbons and Siamangs, often when a father dies and is replaced by his son. Nonreproductive sexual behaviors such as oral sex are also commonly performed in non-incestuous contexts, e.g., between a pair-bonded male and female. Cunnilingus (including direct clitoral licking), manual fondling of the vulva, and vaginal penetration with the fingers have all been observed in mated pairs. Females probably also experience orgasm during heterosexual encounters: in one episode in which a male and female were thrusting against each other, a shudder coursed through the female’s body, and she remained still for almost half a minute after a period of intense stimulation. Female White-handed Gibbons sometimes masturbate by rubbing their genitals against a surface, and they may experience orgasm this way; male Siamangs also masturbate, though not necessarily to orgasm.

In White-handed Gibbons, about 6-7 percent of heterosexual copulations occur when the female cannot conceive, e.g., during pregnancy or lactation. Some of these matings may be with males other than her mate. Although most Gibbon pairs are monogamous, it is estimated that 10-12 percent of White-handed Gibbon copulations are promiscuous. Nonmonogamous sexual activity also occurs in Siamangs and may be initiated by the female. Similarly, although many Gibbons (of both species) pair for life, divorce also occurs. In one study that followed 11 Gibbon heterosexual pairs over six years, 5 of them split up—usually when one partner left his or her mate to be with another individual. As a result, many White-handed Gibbon families—perhaps up to a third—involve step-parenting. Interestingly, even though there is a wide variety of possible sexual and pairing activities in these species, heterosexual activity is a relatively rare occurrence in wild Gibbons. For example, sexual behavior between male and female White-handed Gibbons generally occurs only once every two years or so, and for periods of only four or five months at a time when it does (females generally breed only every two to three years). In Siamangs, females go through regular periods of asexuality in which they delay breeding and turn over the care of their young to males. Females of this species look after their young only until they are 12-16 months old; at that time, males assume full responsibility for the offspring, but females do not reproduce again for another year. It is thought that this period of nonreproduction enables them to assume leadership roles in their group.

*asterisked references discuss homosexuality/transgender

Brockelman, W. Y., U. Reichard, U. Treesucon, and J. J. Raemaekers (1998) “Dispersal, Pair Formation, and Social Structure in Gibbons (Hylobates lar).” Behavioral Ecology and Sociobiology 42:329-39.

Chivers, D. J. (1974) The Siamang in Malaya: A Field Study of a Primate in Tropical Rain Forest. Contributions to Primatology, vol. 4. Basel: S. Karger.

———. (1972) “The Siamang and the Gibbon in the Malay Peninsula.” In D. M. Rumbaugh, ed., Gibbon and Siamang, vol.1, pp. 103-35. Basel: S. Karger.

Chivers, D. J., and J. J. Raemaekers (1980) “Long-term Changes in Behavior.” In D. J. Chivers, ed., Malayan Forest Primates: Ten Years’ Study in Tropical Rain Forest, pp. 209-60. New York: Plenum.

*Edwards, A.-M. A. R., and J. D. Todd (1991) “Homosexual Behavior in Wild White-handed Gibbons (Hylobates lar).” Primates 32:231-36.

Ellefson, J. O. (1974) “A Natural History of White-handed Gibbons in the Malayan Peninsula.” In D. M. Rumbaugh, ed., Gibbon and Siamang, vol. 3, pp. 1-136. Basel: S. Karger.

*Fox, G. J. (1977) “Social Dynamics in Siamang.” Ph.D. thesis, University of Wisconsin-Milwaukee.

———(1972) “Some Comparisons Between Siamang and Gibbon Behavior.” Folia Primatologica 18:122- 39.

Koyama, N. (1971) “Observations on Mating Behavior of Wild Siamang Gibbons at Fraser’s Hill, Malaysia.” Primates 12:183-89.

Leighton, D. R. (1987) “Gibbons: Territoriality and Monogamy.” In B. B. Smuts, D. L. Cheney, R. M. Seyfarth, R. W. Wrangham, and T. T. Struhsaker, eds., Primate Societies, pp. 135-45. Chicago: University of Chicago Press.

Mootnick, A. R., and E. Baker (1994) “Masturbation in Captive Hylobates (Gibbons).” Zoo Biology 13:345- 53.

Palombit, R. (1996) “Pair Bonds in Monogamous Apes: A Comparison of the Siamang Hylobates syndacty-lus and the White-handed Gibbon Hylobates lar.” Behavior 133:321-56.

———(1994a) “Dynamic Pair Bonds in Hylobatids: Implications Regarding Monogamous Social Systems.” Behavior 128:65-101.

———(1994b) “Extra-pair Copulations in a Monogamous Ape.” Animal Behavior 47:721-23.

Raemaekers, J. J., and P. M. Raemaekers (1984) “Vocal Interaction Between Two Male Gibbons, Hylobates lar.” Natural History Bulletin of the Siam Society 32:95-106.

Reichard, U. (1995a) “Extra-pair Copulation in Monogamous Wild White-handed Gibbons (Hylobates lar).” Zeitschrift für Säugetierkunde 60:186-88.

———(1995b) “Extra-pair Copulation in a Monogamous Gibbon (Hylobates lar).” Ethology 100:99-112.

LANGURS AND LEAF MONKEYS

Hanuman Langurs live in cosexual troops (some contain only one male) and also in all-male groups. The latter typically include up to 30 or more individuals; about 20 percent of the population in some areas lives in male-only groups. Nilgiri Langurs live in both cosexual troops (usually eight to nine monkeys each, with one or two adult males) and same-sex groupings (usually two or three males, occasionally more, constituting about a quarter to a third of the adult males). Troop life and stability generally revolve around the females; males are distinctly peripheral to the overall social system, playing only a minor role in defending the troop and minimally helping raise the young.

Behavioral Expression: Homosexual mounting is a prominent feature of female interactions in Hanuman Langurs. One female climbs on the back of another and begins pelvic thrusting. Unlike in other species that engage in homosexual mounting, the female does not rub her genitals on the rump of the other female, but rather thrusts against her buttocks. The mounter may experience indirect stimulation of the area surrounding her clitoris, while the mountee may have direct clitoral stimulation from the female on top of her. In many ways such mounts resemble heterosexual matings, for example in their duration (5 to 10 seconds), number of pelvic thrusts (two to eleven), the grunting and grimacing of the mounter, and the JUMPING DISPLAY, which often precedes or follows. In other respects, however, homosexual mountings are strikingly different. For example, most heterosexual matings are solicited by the female, who lowers her head and shakes it while presenting her hindquarters to the male. While a similar solicitation occurs in about 13 percent of mounts between females, the majority (79 percent) are initiated by the mounting female. In both homosexual and heterosexual mounts, the partners groom following a mount; however, between females the mounter usually grooms the mountee, while in heterosexual mounts, the mountee (female) typically grooms the mounter (male). Finally, only about 30 percent of homosexual mounts are interrupted by other individuals; in contrast, more than 80 percent of heterosexual copulations are harassed by other animals trying to disrupt (and prevent) the mating. Up to seven animals of all ages and sexes may converge on an opposite-sex mating pair and directly attack the animals, slapping them, trying to push the male off or chase the female out from under him, and even kicking the male’s testicles.

All females participate freely in homosexual mounting, including lactating, pregnant, menstruating, ovulating, and nonovulating females. This behavior is especially common among mothers, who have developed a special “baby-sitting” system: they transfer their young to other individuals in the troop (usually other females but sometimes males) for a short time (a similar pattern is found in Nilgiri Langurs). This allows them to engage in homosexual (and other) activities. Most mounting between females occurs among adults, though some involves adults with juveniles (up to four years old), usually with the younger female mounting the older one. Although most homosexual participants are unrelated, some mountings are incestuous, mostly between half sisters (about 27 percent of all lesbian mounts) and, more rarely, between mother and daughter (about 1 percent of mounts); heterosexual matings are virtually never incestuous.

Male Hanuman Langurs mount each other as well, especially in the all-male bands. Unlike homosexual mounting between females, this activity is typically initiated by the mountee, who invites another male to mount him by performing a head-shaking display (sometimes combined with small jumps and “snoring” vocalizations). Mounting often involves one male rubbing and thrusting his erect penis against the other’s body and may be accompanied by a number of affectionate activities that are typically associated with sexual arousal. These include embracing (in which one male buries his head in the chest or shoulder of another), mouth-to-mouth contact or “kissing,” reciprocal grooming (often accompanied by erections), and touching or grooming of the genitals with the hand or lips. Males also “cuddle,” one sitting closely behind the other, resting his head on the back of the male seated between his legs while touching his loins. Hanuman males sometimes form DOUS—companionships in which two males live and travel together, visiting troops in other areas or sometimes settling into all-male bands. Some duos are short-lived (a month or less), others more long-lasting.

Male Nilgiri Langurs also interact erotically with each other in a number of ways, usually incorporating three types of activities: grooming, embracing, and mounting. These are not entirely separate behaviors, and they often combine with each other. Grooming is an intensely pleasurable, relaxing, and arousing experience: one or both males usually get an erection during grooming, and this may lead to ejaculation (a male may even eat his own semen afterward). In embracing, one monkey runs up to another and gives him a long, clinging hug; this is often combined with grooming and has a noticeable soothing effect. Male Nilgiri Langurs also mount each other, using the same position as for heterosexual intercourse. One male may directly approach another male and present his hindquarters to the other, or else he may go through a more stylized presentation known as REAR-END FLIRTATION, in which he slowly walks by the other male and turns his hindquarters toward him as he passes by. During same-sex mounting, one male climbs on top of the other’s rump, grabbing the mounted monkey by the ankles with his feet while making pelvic thrusts (often simultaneously mouthing his back); the mountee sometimes looks or reaches back to grasp the other male. Following mounting, the monkeys often groom or embrace-groom. In cosexual troops with more than one male, two males who engage in homosexual mounting may cooperate in launching attacks against males in neighboring groups.

Intersexual Hanuman Langurs also occur: for example, anatomically male animals with female chromosomes (XX) have been documented. This is thought to be the result of a “sex change” in the chromosomal structure of the animal.

Frequency: Female homosexual mounting is a common and regular occurrence in Hanuman Langurs, comprising 37 percent of all mounting activity in some regions; each female participates in a homosexual mount roughly once every five days, usually in the morning or late afternoon. There is also considerable geographic variation in the frequency of mounting between females. Male homosexual mounting in both Hanuman and Nilgiri Langurs is less common, though it can occur frequently in Hanuman all-male bands (especially during periods of excitement). In one study, more than 40 homosexual interactions between male Hanumans were observed during three months. Among Nilgiri Langur males, nearly half of all grooming sessions are between males and over 10 percent of embracing is between males.

Orientation: All female Hanuman Langurs participate in homosexual activity, to varying degrees; most females are probably bisexual, also mating heterosexually to a greater or lesser extent. Male Hanuman Langurs are probably sequentially bisexual, since each male spends some part of his life in an all-male band, where homosexual activities typically occur—and at any given time, as much as 75-90 percent of the male population may be living in such bands. Some males are exclusively homosexual for long periods, since they may stay in these bands for more than five years—in some cases, decade-long residencies have been documented. In fact, some males never mate heterosexually, since they spend their entire adult lives in all-male bands. The highest-ranking male in a Nilgiri Langur troop engages in both homosexual and heterosexual mounting. The other males in the group, however, participate only in homosexual mounting during their stay in the troop, which can last for four or more years.

A large proportion of male Hanuman Langurs are nonbreeding: about a quarter of all males never reproduce during their lifetime, and (as noted above) the majority of the male population lives in all-male bands. Individual females occasionally go through nonbreeding periods in which menstruation may cease for months at a time. Furthermore, both males and females experience a postreproductive or “menopausal” period later in their lives: about 14 percent of the female population consists of nonbreeding older females who nevertheless are still sexually active. This period can last up to nine years, fully one-quarter of the average female’s life span. Males frequently rejoin all-male bands after they have bred, where they live out the remainder of their lives (six or more years). Langurs also participate in a variety of nonprocreative sexual behaviors during their breeding prime: in Hanumans, about 8 percent of copulations occur outside of the female’s fertilizable period, while sexual activity during pregnancy is common (especially during the second and third months of the six-to-seven-month gestation period). Females also occasionally mount males, while adult-juvenile heterosexual interactions also occur. Male Nilgiri Langurs often masturbate, and in some populations of this species, heterosexual mating is remarkably infrequent. In fact, the sexes often lead largely separate lives: adult males and females hardly ever interact with one another, and most social interactions take place within small subgroups consisting of monkeys of the same sex and age.

The breeding system of Hanuman Langurs is in many ways characterized by hostility and violence between the sexes and toward infants. As mentioned above, group members often harass and disrupt heterosexual matings, with the result that less than half of all copulations are completed (harassment also occurs in more than three-quarters of Nilgiri Langur copulations). Moreover, a systematic pattern of infanticide is prominent in Hanuman Langurs: males attempting to gain sexual access to females often brutally kill their infants. In some populations, infanticide accounts for as many as 30-60 percent of all infant deaths. The stress of male takeover attempts also sometimes results in abortion of fetuses, and in a few cases females even appear to induce the abortions themselves rather than have their babies subsequently killed by a male. For example, pregnant females may press and slide their bellies on the ground or allow other females to climb on or jump forcefully against them. During the raising of infants, abuse and neglect by females is also not uncommon, occurring in 12 percent of mother-infant interactions and 17 percent of “baby-sitter” interactions. Mistreatment includes abandonment; dangling, dropping, or dragging of the baby; shoving it against the ground; biting; and even kicking and throwing infants out of trees. Remarkably, infants are rarely seriously hurt as a result of such behaviors, although a few deaths (including choking) have been documented. In addition, young females from one group sometimes “kidnap” a baby from a neighboring group, keeping the infant for up to 33 hours before its mother is able to retrieve it. Occasionally the stolen baby dies as a result of the mishandling or neglect it experiences during a kidnapping.

*asterisked references discuss homosexuality/transgender

Agoramoorthy, G., and S. M. Mohnot (1988) “Infanticide and Juvenilicide in Hanuman Langurs (Presbytis entellus) Around Jodhpur, India.” Human Evolution 3:279-96.

Agoramoorthy, G., S. M. Mohnot, V. Sommer, and A. Srivastava (1988) “Abortions in Free-ranging Hanuman Langurs (Presbytis entellus)—a Male Induced Strategy?” Human Evolution 3:297-308.

Borries, C. (1997) “Infanticide in Seasonally Breeding Multimale Groups of Hanuman Langurs (Presbytis entellus) in Ramnagar (South Nepal).” Behavioral Ecology and Sociobiology 41:139-50.

*Dolhinow, P. (1978) “A Behavioral Repertoire for the Indian Langur (Presbytis entellus).” Primates 19:449- 72.

*Egozcue, J. (1972) “XX Male Presbytis entellus? A Retrospective Study.” Folia Primatologica 17:292-96.

*Hohmann, G. (1989) “Group Fission in Nilgiri Langurs (Presbytis johnii).” International Journal of Primatology 10:441-54.

Hohmann, G., and L. Vogl (1991) “Loud Calls of Male Nilgiri Langurs (Presbytis johnii): Age-, Individual-, and Population-Specific Differences.” International Journal of Primatology 12:503-24.

Hrdy, S. B. (1978) “Allomaternal Care and Abuse of Infants Among Hanuman Langurs.” In D. J. Chivers and J. Herbert, eds., Recent Advances in Primatology, vol. 1, pp. 169-72. London: Academic Press.

*———(1977) The Langurs of Abu: Male and Female Strategies of Reproduction. Cambridge, Mass.: Harvard University Press.

Johnson, J. M. (1984) “The Function of All-Male Trouping Structure in the Nilgiri Langur, Presbytis johnii.” In M. L. Roonwal, S. M. Mohnot, and N. S. Rathore, eds., Current Primate Researches, p. 397. Jodhpur, India: Jodhpur University.

*Mohnot, S. M. (1984) “Some Observations on All-Male Bands of the Hanuman Langur, Presbytis entellus.” In M. L. Roonwal, S. M. Mohnot, and N. S. Rathore, eds., Current Primate Researches, pp. 343-59. Jodhpur, India: Jodhpur University.

———(1980) “Intergroup Infant Kidnapping in Hanuman Langur.” Folia Primatologica 34:259-77.

*Poirier, F. E. (1970a) “The Nilgiri Langur (Presbytis johnii) of South India.” In L. A. Rosenblum, ed., Primate Behavior: Developments in Field and Laboratory Research, vol .1, pp. 251-383. New York: Academic Press.

*———(1970b) “The Communication Matrix of the Nilgiri Langur (Presbytis johnii) of South India.” Folia Primatologica 13:92–136.

———(1969) “Behavioral Flexibility and Intertroop Variation Among Nilgiri Langurs (Presbytis johnii) of South India.” Folia Primatologica 11:119–33.

Rajpurohit, L. S., V. Sommer, and S. M. Mohnot (1995) “Wanderers Between Harems and Bachelor Bands: Male Hanuman Langurs (Presbytis entellus) at Jodhpur in Rajasthan.” Behavior 132:255–99.

Sommer, V. (1989a) “Sexual Harassment in Langur Monkeys (Presbytis entellus): Competition for Nurture, Eggs, and Sperm?” Ethology 80:205–17.

———(1989b) “Infant Mistreatment in Langur Monkeys—Sociobiology Tackled from the Wrong End?” In A. E. Rasa, C. Vogel, and E. Voland, eds., The Sociobiology of Sexual and Reproductive Strategies, pp. 110-27. London and New York: Chapman and Hall.

*———(1988) “Female-Female Mounting in Langurs (Presbytis entellus).” International Journal of Primatology 8:478.

Sommer, V., and L. S. Rajpurohit (1989) “Male Reproductive Success in Harem Troops of Hanuman Langurs (Presbytis entellus).” International Journal of Primatology 10:293–317.

Sommer, V., A. Srivastava, and C. Borries (1992) “Cycles, Sexuality, and Conception in Free-Ranging Langurs (Presbytis entellus.)” American Journal of Primatology 28:1–27.

*Srivastava, A., C. Borries, and V. Sommer (1991) “Homosexual Mounting in Free-Ranging Female Hanuman Langurs (Presbytis entellus.)” Archives of Sexual Behavior 20:487–516.

Tanaka, J. (1965) “Social Structure of Nilgiri Langurs.” Primates 6:107–22.

Vogel, C. (1984) “Patterns of Infant-Transfer within Two Troops of Common Langurs (Presbytis entellus) Near Jodhpur: Testing Hypotheses Concerning the Benefits and Risks.” In M. L. Roonwal, S. M. Mohnot, and N. S. Rathore, eds., Current Primate Researches, pp. 361–79. Jodhpur, India: Jodhpur University.

*Weber, I. (1973) “Tactile Communication Among Free-ranging Langurs.” American Journal of Physical Anthropology 38:481–86.

*Weber, I., and C. Vogel (1970) “Sozialverhalten in ein- und zweigeschlechtigen Langurengruppen [Social Behavior in Unisexual and Heterosexual Langur Groups].” Homo 21:73–80.

*Weinrich, J. D. (1980) “Homosexual Behavior in Animals: A New Review of Observations From the Wild, and Their Relationship to Human Sexuality.” In R. Forleo and W. Pasini, eds., Medical Sexology: The Third International Congress, pp. 288–95. Littleton, Mass.: PSG Publishing.

Both Proboscis and Golden Monkeys usually live in polygamous groups consisting of one male and several adult females (five on the average), along with several adolescent or juvenile females. Younger male Proboscis Monkeys sometimes join all-male troops before reaching adolescence—such groups contain males of all ages, including adults—while some male Golden Monkeys are solitary or peripheral. Cosexual groups of Proboscis Monkeys are female-centered, since female Proboscis Monkeys direct most of their behaviors—both friendly and aggressive—toward other females rather than males, and such female relationships hold the group together. In many cases females also take the initiative in directing the movement of the group, for example when leaving a sleeping tree or crossing a river. Although little else is known about the social organization of Golden Monkeys, it appears that they may also gather into huge troops—up to 600 animals—which are among the largest groupings found in any tree-living primate.

Behavioral Expression: Both male and female Proboscis Monkeys participate in homosexual mounting. An adult female may mount another from behind, in a position similar to heterosexual mounting, and thrust against her. Such behavior sometimes occurs when two social groups meet each other. Unlike heterosexual copulation, lesbian mounting is usually not preceded by solicitation behavior on the part of the female being mounted (solicitation involves a special “pout” face with pursed lips, shaking of the head from side to side, and presentation of the hindquarters to the mounting animal). Male homosexual mounting—also in the front-to-back position, and with pelvic thrusting—occurs in younger animals (adolescents or juveniles) and is often a part of play-wrestling matches. It may also be interspersed with masturbation, in which the mounting male stimulates his penis with his hand. In some cases, the male being mounted may not be an entirely willing participant and will try to get away as the other male restrains him by biting gently on the neck; similar escape behavior is sometimes shown by females during heterosexual mounting. In Golden Monkeys, homosexual behavior has only been seen among females and again consists of one female mounting another.

Frequency: Same-sex mounting probably occurs only occasionally in Proboscis and Golden Monkeys. However, in Proboscis Monkeys at least, heterosexual mounting is also infrequent: in one study, only 12 mountings were observed over an entire year, and 2 of these (17 percent) were same-sex.

Orientation: Female Proboscis Monkeys that engage in same-sex mounting are probably bisexual, since they may alternate same-sex and opposite-sex activity during the same session. Golden Monkey females probably have a bisexual potential, since same-sex mounting has so far only been observed in captive situations when males are not present, and all such females engaging in same-sex mounting also mated heterosexually and raised young.

As noted above, female Proboscis Monkeys often refuse heterosexual copulation by breaking away from the male during mounting. A male may exhibit indifference to a female’s solicitations as well, either ignoring her completely or snarling at her to indicate his unwillingness. Male Golden Monkeys also frequently ignore females’ sexual invitations: nearly 50 percent of all female invitations fail to result in mounting by the male. Furthermore, many mounts by males do not result in ejaculation: for some Golden males, 18-97 percent of their copulations are nonejaculatory. Females, however, display an intense interest in sexual activity, frequently soliciting the male and copulating repeatedly—one female solicited a male 34 times, and was mounted 23 times, in one day. REVERSE mountings, in which the female mounts the male, are common in Golden Monkeys as well, accounting for anywhere from 3-40 percent of all heterosexual mounts. In such cases, the male usually adopts the prostrate solicitation posture typical of females inviting copulation. Heterosexual copulations in Proboscis Monkeys are sometimes also harassed or interrupted by younger animals, who try to disrupt the mating pair by climbing on the male, pulling at his nose, or making noises and distracting movements. Female Proboscis Monkeys often have sex when they are pregnant, in some cases soliciting copulations from males as late as two weeks before birth. In fact, heterosexual mating may occur more frequently during pregnancy than at any other time of the year. Golden Monkeys engage in sexual mounting outside of the mating season, and females often solicit sexual behavior while they are menstruating. As noted above, masturbation in Proboscis Monkeys may occur in same-sex contexts; similar behavior has been observed in heterosexual contexts among Golden Monkeys. In such cases, both males and females may eat the semen after ejaculation. A number of adult, sexually mature Proboscis males are nonbreeders, since they live in all-male groups: in one population, such individuals comprised 28 percent of all adult males. Solitary male Golden Monkeys are probably also nonbreeders.

*asterisked references discuss homosexuality/transgender

Clarke, A. S. (1991) “Sociosexual Behavior of Captive Sichuan Golden Monkeys (Rhinopithecus roxellana).” Zoo Biology 10:369-74.

Gorzitze, A. B. (1996) “Birth-related Behaviors in Wild Proboscis Monkeys (Nasalis larvatus).” Primates 37:75-78.

Kawabe, M., and T. Mano (1972) “Ecology and Behavior of the Wild Proboscis Monkey, Nasalis larvatus (Wurmb) in Sabah, Malaysia.” Primates 13:213-27.

Poirier, F. E., and H. Hongxhin (1983) “Macaca mulatta and Rhinopithecus in China: Preliminary Research Results.” Current Anthropology 24:387-88.

Qi, J.-F. (1988) “Observation Studies on Reproduction of Golden Monkeys in Captivity: I. Copulatory Behavior.” Acta Theriologica Sinica 8:172-75.

*Ren, R., K. Yan, Y. Su, H. Qi, B. Liang, W. Bao, and F. B. M. de Waal (1995) “The Reproductive Behavior of Golden Monkeys in Captivity.” Primates 36:135-43.

———(1991) “The Reconciliation Behavior of Golden Monkeys (Rhinopithecus roxellanae roxellanae) in Small Breeding Groups.” Primates 32:321-27.

Schaller, G. B. (1985) “China’s Golden Treasure.” International Wildlife 15:29-31.

*Yeager, C. P. (1990a) “Notes on the Sexual Behavior of the Proboscis Monkey.” American Journal of Primatology 21:223-27.

———(1990b) “Proboscis Monkey (Nasalis larvatus) Social Organization: Group Structure.” American Journal of Primatology 20:95-106.

MACAQUES

Japanese Macaques live in cosexual troops of 20–100 individuals, subdivided into smaller matrilineal groups composed of numerous related females and several unrelated males. Males usually leave their birth group on reaching maturity and may even periodically transfer to different groups, live in all-male groups, or become solitary or peripheral. Females, in contrast, generally remain in their home group for life. As a result, the group is centered around the kinship and bonding between females (and some groups have only one regular adult male member).

Behavioral Expression: Female Japanese Macaques form intense, exclusive pair-bonds with each other based on mutual sexual attraction. These pairings are known as CONSORTSHIPS and are characterized by a number of distinctive affectionate, sexual, and social activities. Female partners in a consortship typically sit together, huddling or in close physical contact, and often spend long periods grooming one another between their sexual interactions. They also synchronize their movements, including traveling in tandem and persistently following one another, and may make cooing sounds toward one another. Consorts become agitated when another animal approaches or intrudes, responding with threats, shudders, vocalizing, or withdrawal. They sometimes actively separate themselves from their relatives (temporarily forgoing the time they would usually spend grooming their young or other kin), even occasionally withdrawing from the main troop as a whole. Partners in homosexual consortships often forge strong supportive “alliances” with each other, defending their partner and intervening on her behalf when she is threatened by another individual. Most such interventions do not disrupt the traditional hierarchy or rank system of the troop. However, some interventions are termed REVOLUTIONARY because partners challenge higher-ranking individuals, while others are ARBITRATING interventions, involving mediation between individuals with more ambiguous rankings. Females also actively compete with individuals of both sexes for access to other females as sexual partners, sometimes even incurring severe injuries when they challenge intruding males. Consortships typically last from a few days to several weeks during the mating season, although partners often develop a strong friendship as a result of a consortship and remain bonded throughout the year (in contrast to heterosexual consortships, which generally do not extend beyond the mating season). Females are often serially monogamous, forming several exclusive consortships sequentially during the mating season, although they generally have fewer partners than individuals engaging in heterosexual or male homosexual activities. Homosexual pairings occur among females of all ages, from adolescents to the very old, and sometimes an adult female will pair with a pubescent female. Interestingly, an incest taboo is in effect for homosexual but not heterosexual consortships: females never choose close relatives (mothers, sisters, daughters, granddaughters, first cousins) as partners, whereas brother-sister and mother-son consorts do occasionally occur. Aunts and nieces, however, do not generally recognize each other as kin in this species, and so they sometimes consort together.

As signaled by the reddening of their faces and sexual skin (which also swells), females in consortships are usually “in heat,” and sexual activity is a regular and prominent feature of these homosexual pairings. Females engage in a variety of behaviors that involve genital stimulation, usually in the form of one female mounting another. Fully seven different positions are used for homosexual copulation (as well as for heterosexual mating, although with different frequencies). Most commonly, one female sits or lies on the back of the other, making pelvic thrusts and rubbing her clitoris against her partner’s rump. The mountee’s clitoris maybe stimulated by her partner’s thrusting or with her own tail. Two females also sometimes embrace each other in a face-to-face position and rub their genitals together, either lying down or “sitting in each other’s lap”; these postures are more common in lesbian interactions than heterosexual ones. Other positions include the “double-foot-clasp” (one female mounts from behind, grasping her partner’s ankles or thighs with her feet); rear mounts where the mounter keeps her feet on the ground; and thrusting against the partner in sideways or variable postures. During mounting, females sometimes make vocalizations such as hoarse, cackling ko-ko-ko-ko sounds. Females being mounted commonly reach back and grab their partner, gazing intensely into her eyes and grimacing, while the mounter clutches the fur on her partner’s back—indications that both females probably experience orgasm during homosexual interactions. Consorts usually mount each other in a series of three or more consecutive mounts (as in heterosexual mating), and mounting is often reciprocal (partners exchange positions). In addition to mounting and genital rubbing, consorts occasionally suck each other’s nipples. Sexual interactions are frequently initiated by the mountee, who performs a number of characteristic “courtship” behaviors to solicit or “demand” a mount from her consort. She may slap the ground while shrieking, run away from her partner and then return while presenting her hindquarters, or else display a variety of other behaviors such as head bobbing, vocalizing, arching of the back, lip quivering, intense staring, and even spasms and more aggressive pushing and grabbing. All of these are distinct from heterosexual courtship, in which the female usually invites the male to mount by slowly inching toward him in a sitting position, with mutual flipping of ears and eyebrows. A wide variety of sounds are used in both heterosexual and homosexual courtships, including cooing, whistling, warbling, squawking, chirping, barking, and squeaking—the latter is more typical of interactions between females, however.

Male Japanese Macaques also mount each other. They do not generally form homosexual consortships—indeed, some males mount up to 24 different partners—but some individuals do have certain preferred partners, usually of the same age. Males also sometimes engage in affectionate and playful activities in combination with their sexual interactions, including touching, huddling, and grooming. Unlike heterosexual and lesbian interactions, most mounts between males are single (rather than series) and are generally briefer, although they can still involve full erections, pelvic thrusting, penetration, and/or ejaculation. The double-foot-clasp is the preferred posture between males, and sitting or lying on the partner’s back is rarely if ever used. Young males often make a distinctive purring or churring sound deep in the throat while mounting each other; this vocalization is not heard in heterosexual contexts. Sexual activity between males differs from male-female behavior in a number of other ways: homosexual mounting is more common outside or toward the end of the breeding season, while heterosexual mounts are more frequently interrupted by other individuals than mounts between males.

Frequency: The prevalence of homosexual activity in Japanese Macaques varies greatly between different troops, although it can be found to some degree in virtually every population. In some cases, more than a quarter of all consortships are between females and up to a third or more of all mounting episodes are homosexual; five to ten mounts between males may occur each morning in some troops. In other troops, same-sex behavior is much less frequent.

Orientation: Again, the proportion of the female population participating in homosexual activity is highly variable, ranging from 12–78 percent, averaging 43 percent (in semiwild troops). In some troops, all females that participate in same-sex consortships are bisexual, also consorting with males; however, while paired with a female they remain faithful to their partner, ignoring or rebuffing any advances made by males toward them. In other troops, though, some females are exclusively lesbian, engaging in sexual interactions only with females: in these cases, an average of 9 percent of females are homosexual, 56 percent bisexual, and 35 percent exclusively heterosexual. Among males, there is a similar variation in the proportion of individuals participating in homosexual mounting, from as low as 0–15 percent, to virtually all the males in a troop. Generally, though, males that engage in same-sex activity also participate in opposite-sex mounting. Interestingly, some of the most intense homosexual activity, involving complete mounts with ejaculation, is exhibited by males who are also the most active heterosexually.

Nonprocreative heterosexual activities are a prominent feature of Japanese Macaque life. In some populations, as many as three-quarters of all females actively seek sexual interactions while they are pregnant, half do so while menstruating, and individual females may copulate with an average of ten different males during the mating season. Most heterosexual mounts (nearly two-thirds) do not lead to ejaculation. In addition, REVERSE mounting is common, in which a female climbs on top of a male and rubs her genitals on his back. In some troops, about 40 percent of all females engage in this behavior and it occurs in about a third of all heterosexual interactions. Masturbation is also common in both males and females. Females in some troops frequently form consortships with sexually immature (preadolescent) males; as noted above, incestuous pairings also sometimes occur, and up to 15 percent of heterosexual mountings may be between related individuals.

Heterosexual mating occurs year round, but rarely leads to pregnancy when it takes place outside of the breeding season. Nor are females unique in experiencing a sexual cycle with distinct nonreproductive periods: males undergo a yearly seasonal fluctuation in their hormone levels that results in retraction of their testicles, cessation of ejaculation, and loss of color in their sexual skin during the nonmating season. In addition, approximately 10 percent of Japanese Macaques in some troops form nonbreeding or celibate heterosexual pairs: the partners specifically avoid sexual activities with each other, although they may interact sexually with other individuals. Many females also experience a long postreproductive period later in their lives, generally lasting four to five years and constituting about 16 percent of the average life span. Such individuals continue to be sexually active, copulating with males at rates comparable to those of breeding females and also interacting with the same number of female sexual partners as do younger females.

In some troops, a unique form of “baby-sitting” has developed. Although males in this species do not typically participate in parenting, high-ranking males in some populations take care of infants that are not their own for short periods. They groom, carry, embrace, and protect the infants, usually with the consent of their mothers. A few females also act as baby-sitters; however, nonbreeding females have also been known to kidnap infants, sometimes keeping them permanently. In addition, a few male caretakers interact sexually with infants (usually females), masturbating themselves while carrying them or even thrusting against them.

*asterisked references discuss homosexuality/transgender

*Chapais, B., C. Gauthier, J. Prud’homme, and P. Vasey (1997) “Relatedness Threshold for Nepotism in Japanese Macaques.” Animal Behavior 53:1089–1101.

*Chapais, B., and C. Mignault (1991) “Homosexual Incest Avoidance Among Females in Captive Japanese Macaques.” American Journal of Primatology 23:171–83.

*Corradino, C. (1990) “Proximity Structure in a Captive Colony of Japanese Monkeys (Macaca fuscata fuscata): An Application of Multidimensional Scaling.” Primates 31:351–62.

*Eaton, G. G. (1978) “Longitudinal Studies of Sexual Behavior in the Oregon Troop of Japanese Macaques.” In T. E. McGill, D. A. Dewsbury, and B. D. Sachs, eds., Sex and Behavior: Status and Prospectus, pp. 35–59. New York: Plenum Press.

*Enomoto, T. (1974) “The Sexual Behavior of Japanese Monkeys.” Journal of Human Evolution 3:351–72.

*Fedigan, L. M. (1982) Primate Paradigms: Sex Roles and Social Bonds. Montreal: Eden Press.

*Fedigan, L. M., and H. Gouzoules (1978) “The Consort Relationship in a Troop of Japanese Monkeys.” In D. Chivers, ed., Recent Advances in Primatology, vol. 1: pp. 493–95. London: Academic Press.

*Gouzoules, H., and R. W. Goy (1983) “Physiological and Social Influences on Mounting Behavior of Troop-Living Female Monkeys (Macaca fuscata).” American Journal of Primatology 5:39–49.

*Green, S. (1975) “Variation of Vocal Pattern with Social Situation in the Japanese Monkey (Macaca fuscata): A Field Study.” In L. A. Rosenblum, ed., Primate Behavior: Developments in Field and Laboratory Research, vol. 4, pp. 1–102. New York: Academic Press.

*Hanby, J. P. (1974) “Male-Male Mounting in Japanese Monkeys (Macaca fuscata).” Animal Behavior 22:836–49.

*Hanby, J. P., and C. E. Brown (1974) “The Development of Sociosexual Behaviors in Japanese Macaques Macaca fuscata.” Behavior 49:152–96.

*Hanby, J. P., L. T. Robertson, and C. H. Phoenix (1971) “The Sexual Behavior of a Confined Troop of Japanese Macaques.” Folia Primatologica 16:123–43.

Itani, J. (1959) “Paternal Care in the Wild Japanese Monkey, Macaca fuscata fuscata.” Primates 2:61–93.

*Lunardini, A. (1989) “Social Organization in a Confined Group of Japanese Macaques (Macaca fuscata). An Application of Correspondence Analysis.” Primates 30:175–85.

*Rendall, D., and L. L. Taylor (1991) “Female Sexual Behavior in the Absence of Male-Male Competition in Captive Japanese Macaques (Macaca fuscata).” Zoo Biology 10:319–28.

*Sugiyama, Y. (1960) “On the Division of a Natural Troop of Japanese Monkeys at Takasakiyama.” Primates 2:109–48.

*Takahata, Y. (1982) “The Socio-sexual Behavior of Japanese Monkeys.” Zeitschrift für Tierpsychologie 59:89–108.

*———(1980) “The Reproductive Biology of a Free-Ranging Troop of Japanese Monkeys.” Primates 21:303–29.

Takahata, Y., N. Koyama, and S. Suzuki (1995) “Do the Old Aged Females Experience a Long Postreproductive Life Span?: The Cases of Japanese Macaques and Chimpanzees.” Primates 36:169–80.

*Tartabini, A. (1978) “An Analysis of Dyadic Interactions of Male Japanese Monkeys (Macaca fuscata fuscata) in a Cage-Room Observation.” Primates 19:423–36.

Tokuda, K. (1961) “A Study on the Sexual Behavior in the Japanese Monkey Troop.” Primates 3:1–40.

*Vasey, P. L (1998) “Female Choice and Inter-sexual Competition for Female Sexual Partners in Japanese Macaques.” Behavior 135:1–19.

*———(1996–98) Personal communication.

*———(1996) “Interventions and Alliance Formation Between Female Japanese Macaques, Macaca fuscata, During Homosexual Consortships.” Animal Behavior 52:539–51.

*Vasey, P. L., B. Chapais, and C. Gauthier (1998) “Mounting Interactions Between Female Japanese Macaques: Testing the Influence of Dominance and Aggression.” Ethology 104:387–98.

*Wolfe, L. D. (1986) “Sexual Strategies of Female Japanese Macaques (Macaca fuscata).” Human Evolution 1:267–75.

*———(1984) “Japanese Macaque Female Sexual Behavior: A Comparison of Arashiyama East and West.” In M. F. Small, ed., Female Primates: Studies by Women Primatologists, pp. 141–58. New York: Alan R. Liss.

*———(1979) “Behavioral Patterns of Estrous Females of the Arashiyama West Troop of Japanese Macaques (Macaca fuscata).” Primates 20:525–34.

*Wolfe, L. D., and M. J. S. Noyes (1981) “Reproductive Senescence Among Female Japanese Macaques (Macaca fuscata fuscata).” Journal of Mammology 62:698–705.

Rhesus Macaques live in troops numbering up to 80–100 individuals. These are composed of several cosexual subgroups (averaging around 18 members) organized along matrilineal kinship. Males typically leave their subgroup during adolescence and establish themselves elsewhere—sometimes in all-male groups—leaving the female line of descent intact.

Behavioral Expression: In female Rhesus Macaques, homosexual behavior usually takes place in a CONSORTSHIP, a type of pair-bond between two females that can last anywhere from a few days to many months (consortships are also characteristic of heterosexual relations). Two consorts follow and spend a great deal of time with each other, and participate in a wide variety of courtship, affectionate, and sexual activities; consort partners also sometimes cooperate in attacking other individuals. Females might consort with several other females, although most have only one partner. Lesbian courtship is highly distinctive, and involves five different playful pursuit games: “hide-and-seek,” in which two females peek at each other from around a tree trunk; “kiss and run,” in which one female rushes up to another and briefly kisses or nuzzles her before running off, the other in pursuit; “follow the leader,” in which the females alternate positions following one another; “lipsmack and circle,” where one female circles closer and closer to the other while making lip-smacking noises; and “present and run,” where one female invites the other to mount her and then teasingly runs off.

Sexual activity usually involves one female mounting the other, either in the position used for heterosexual mounting (with the mounter’s feet on the mountee’s legs), or in a position unique to homosexual mounting, in which one female climbs directly on the back of the other female and rubs her genitals on the mountee’s rump. Mounting from the side also occurs. The mounter sometimes stimulates her clitoris or has her partner do it for her, during a mount. Both females show signs of orgasm: the mounter often “pauses” the way a male does at the moment of ejaculation, while the mountee often reaches back and clutches her partner. In some consortships the two females mount each other reciprocally, although in many cases one female is consistently the mounter and her partner always the mountee. Sometimes two females also participate in sexual hugging, in which they wrap their arms and legs around each other while one or both of them engage in clitoral stimulation (including rubbing their genitals on the ground). Combined with sexual stimulation, females also kiss (touching lips or tongues), caress each other’s face, gently bite one another’s ears, and groom each other. Pregnant females sometimes participate in homosexual mounting and consortships as well. Occasionally, females behave aggressively toward a female sexual partner, as also seen in heterosexual interactions (see below).

Male Rhesus Macaques also mount each other, sometimes within a consortship as well. Mounting can include full anal penetration and ejaculation, or else simple thrusting against the partner. Sometimes the mounted male masturbates himself or his partner, and reciprocal mounting is also common (in which the two males take turns mounting each other). In some cases, one male performs a series of mounts one after the other on his partner, as in heterosexual mating. Homosexual activity may be accompanied by grooming or play-wrestling, and the two partners in a consortship can be highly affectionate toward each other, with extended periods of touching, holding, and embracing. Mounting between brothers has also been observed, as well as with males of other species such as Crab-eating Macaques (in captivity).

Several types of intersexuality occur spontaneously in Rhesus Macaques, including hermaphrodite monkeys whose internal gonads are a combination of ovaries and testes, as well as individuals that have female external genitalia but are missing a female sex chromosome and have no ovaries.

Frequency: In wild and semiwild populations of Rhesus Macaques, anywhere from 16 percent to 47 percent of mounting is between animals of the same sex; the majority of homosexual mounting (84 percent) is between males. Within a lesbian consortship, two females may mount each other more than 200 times over six months, and one couple participated in homosexual mounting more than 1,000 times during that time.

Orientation: Depending on the population, 20–90 percent of females participate in homosexual mounting and/or consortships. The majority of these females are bisexual, since they also engage in heterosexual activity (either concurrently or during other periods of their lives), and some even alternate between same-sex and opposite-sex activities in the same day. At least some females that are bisexual nevertheless do seem to prefer homosexual activity, since they return to their female consorts even after having mated with males; a female consort may also try to “win” her female partner back whenever she is temporarily with a male. In addition, some individuals participate in lesbian consortships more frequently than others and generally have much less contact with the opposite sex. Females may also be generally more receptive to same-sex advances: in one population, for example, only 6 percent of attempted homosexual mounts were rejected, compared to 29 percent of heterosexual attempts. Many male Rhesus Macaques are bisexual as well, and individuals vary in their participation in homosexual versus heterosexual activity. As with females, though, some individuals do seem to show a “preference” for homosexuality, since males may mount each other while ignoring available females. Moreover, in a detailed study of one male homosexual consortship or sexual “friendship” in captivity, both males preferred each other’s company to that of a female and chose each other as sexual partners when given a preference test (even though both were able to perform heterosexually with a female).

Rhesus Macaques are noted for their nonprocreative heterosexual behaviors. Half or more of all pregnant females engage in sexual behavior (including mating), and 12 percent of all copulations involve pregnant females. Some individual males even seem to prefer mating with females after they conceive, since nearly half of their copulations are with pregnant females. In fact, parturition itself sometimes stimulates sexual activity in attendants and onlookers, who may masturbate themselves or even mount the mother shortly after she gives birth. More than 40 percent of menstruating females also engage in sexual activity. The typical pattern for heterosexual copulation includes a large number of nonreproductive mounts, since the male may mount the female up to 100 or more times as part of each “copulation.” Although penetration may occur during each mount, usually only the final mount in the series involves ejaculation. Females often initiate sexual behavior with males and commonly experience orgasm during heterosexual mating. They may also copulate with several different males—in fact, females typically mate with more consort partners than do males, to such an extent that they experience a phenomenon known as VAGINAL OVERFLOW because of the amount of sperm they receive from such multiple matings. Rhesus Macaque females also sometimes mount males—such REVERSE mountings can account for 2–6 percent of all heterosexual mountings. Males may become sexually stimulated while a female is mounting them, masturbating or ejaculating spontaneously, and she may also achieve orgasm from rubbing during the mount. Males often masturbate to ejaculation on their own, while females have been observed fondling and sucking their own nipples. Sexual activity with nonoptimal partners also occurs: males occasionally mount their mothers or sisters (incestuous activity accounts for 12–15 percent of all sexual interactions in some populations), and adult-juvenile sexuality (primarily mounting but also fellatio, including with infants) may account for more than 15 percent of all sexual activity. A wide range of interspecies sexual interactions in captivity have also been observed (including a female Rhesus soliciting copulations from a Dog).

Male Rhesus Macaques have a yearly hormonal cycle with a distinct nonbreeding period. Females also commonly experience a postreproductive or “menopausal” stage later in their lives, in which they no longer breed but may still be sexually active. They may also continue to be valued members of the troop, even contributing to the care and raising of infants and juvenile monkeys. In addition, females of all ages participate in a type of “baby-sitting,” in which individuals—in—cluding nonbreeding monkeys—look after infants belonging to other females (and also act as “attendants” during their births). These “aunts,” as they are sometimes called (though they need not be genetically related to the mother), often protect and take care of the infants. Males (who generally do not participate in parenting) also occasionally engage in similar behavior and may even adopt orphaned infants. In some cases, though, “aunts” engage in aggressive or sexual interactions with the infants as well and may even try to “kidnap” another female’s baby. Mothers are also sometimes abusive toward their own infants—shoving, biting, and stepping on the baby’s head have all been observed, and one study showed that about 11 percent of infants are abused in their first two years of life. In addition, heterosexual relations are often characterized by aggression: males frequently attack and may severely wound females that they mate or consort with.

*asterisked references discuss homosexuality/transgender

*Akers, J. S., and C. H. Conaway (1979) “Female Homosexual Behavior in Macaca mulatta.” Archives of Sexual Behavior 8:63–80.

*Altmann, S. A. (1962) “A Field Study of the Sociobiology of Rhesus Monkeys, Macaca mulatta.” Annals of the New York Academy of Sciences 102:338-435.

*Carpenter, C. R. (1942) “Sexual Behavior of Free Ranging Rhesus Monkeys (Macaca mulatta). I. Specimens, Procedures, and Behavioral Characteristics of Estrus. II. Periodicity of Estrus, Homosexual, Autoerotic, and Non-Conformist Behavior.” Journal of Comparative Psychology 33:113–62.

Conaway, C. H., and C. B. Koford (1964) “Estrous Cycles and Mating Behavior in a Free-ranging Band of Rhesus Monkeys.” Journal of Mammalogy 45:577–88.

*Erwin, J., and T. Maple (1976) “Ambisexual Behavior with Male-Male Anal Penetration in Male Rhesus Monkeys.” Archives of Sexual Behavior 5:9–14.

*Fairbanks, L. A., M. T. McGuire, and W. Kerber (1977) “Sex and Aggression During Rhesus Monkey Group Formation.” Aggressive Behavior 3:241–49.

*Gordon, T. P., and I. S. Bernstein (1973) “Seasonal Variation in Sexual Behavior of All-Male Rhesus Troops.” American Journal of Physical Anthropology 38:221–26. *

Hamilton, G. V. (1914) “A Study of Sexual Tendencies in Monkeys and Baboons.” Journal of Animal Behavior 4:295–318.

*Huynen, M. C. (1997) “Homosexual Interactions in Female Rhesus Monkeys, Macaca mulatta.” In M. Taborsky and B. Taborsky, eds., Contributions to the XXV International Ethological Conference, p. 211. Advances in Ethology no. 32. Berlin: Blackwell Wissenschafts-Verlag.

Kaufmann, J. H. (1965) “A Three-Year Study of Mating Behavior in a Free-Ranging Band of Rhesus Monkeys.” Ecology 46:500–12.

*Kempf, E. J. (1917) “The Social and Sexual Behavior of Infrahuman Primates With Some Comparable Facts in Human Behavior.” Psychoanalytic Review 4:127–54.

*Lindburg, D. G. (1971) “The Rhesus Monkey in North India: An Ecological and Behavioral Study.” In L. A. Rosenblum, ed., Primate Behavior: Developments in Field and Laboratory Research, vol. 2, pp. 1–106. New York: Academic Press.

Loy, J. D. (1971) “Estrous Behavior of Free-Ranging Rhesus Monkeys (Macaca mulatta).” Primates 12:1-31.

———(1970) “Peri-Menstrual Sexual Behavior Among Rhesus Monkeys.” Folia Primatologica 13:286-97.

Michael, R. P., M. I. Wilson, and D. Zumpe (1974) “The Bisexual Behavior of Female Rhesus Monkeys.” In R. C. Friedman, ed., Sex Differences in Behavior, pp. 399–412. New York: John Wiley & Sons.

Missakian, E. A. (1973) “Genealogical Mating Activity in Free-Ranging Groups of Rhesus Monkeys (Macaca mulatta) on Cayo Santiago.” Behavior 45:225–41.

Partch, J. (1978) “The Socializing Role of Postreproductive Rhesus Macaque Females.” American Journal of Physical Anthropology 48:425.

*Reinhardt, V., A. Reinhardt, F. B. Bercovitch, and R. W. Goy (1986) “Does Intermale Mounting Function as a Dominance Demonstration in Rhesus Monkeys?” Folia Primatologica 47:55–60.

Rowell, T. E., R. A. Hinde, and Y. Spencer-Booth (1964) “‘Aunt’-Infant Interaction in Captive Rhesus Monkeys.” Animal Behavior 12:219–26.

*Sade, D. S. (1968) “Inhibition of Son-Mother Mating Among Free-Ranging Rhesus Monkeys.” In J. H. Masserman, ed., Animal and Human, pp. 18–38. Science and Psychoanalysis, vol. 12. New York: Grune & Stratton.

Schapiro, S. J., and G. Mitchell (1983) “Infant-Directed Abuse in a Seminatural Environment: Precipitating Factors.” In M. Reite and N. G. Caine, eds., Child Abuse: The Nonhuman Primate Data, pp. 29–48. Monographs in Primatology, vol.1. New York: Alan R. Liss.

*Sullivan, D. J., and H. P. Drobeck (1966) “True Hermaphrodism in a Rhesus Monkey.” Folia Primatologica 4:309–17.

Tilford, B. (1981) “Nondesertion of a Postreproductive Rhesus Female by Adult Male Kin.” Journal of Mammalogy 62:638–39.

Vessey, S. H., and D. B. Meikle (1984) “Free-Living Rhesus Monkeys: Adult Male Interactions with Infants and Juveniles.” In D. M. Taub, ed., Primate Paternalism, pp. 113–26. New York: Van Nostrand Reinhold.

*Weiss, G., R. F. Weick, E. Knobil, S. R. Wolman, and F. Gorstein (1973) “An X-O Anomaly and Ovarian Dysgenesis in a Rhesus Monkey.” Folia Primatologica 19:24–7.

Few field studies of Stumptail Macaques have been conducted, so little is known of their social organization in the wild. They generally appear to live in cosexual groups of 20–50 individuals with a matrilineal organization. The mating system is probably polygamous or promiscuous, involving copulations with multiple partners and little male parental involvement.

Behavioral Expression: Male Stumptails form intense sexual “friendships” with each other, within which an extraordinary variety of homosexual activities are expressed. One male may develop strong affectionate bonds with another male, as shown by their embracing, gently nibbling at each other’s mouth, and huddling together. The two partners may even sleep together, one closely hugging the other from behind while holding his partner’s penis. The affection between these males is also expressed through sexual activity, ranging from mounting to oral sex to mutual masturbation. Mounting occurs in the typical front-to-back position found in heterosexual mating; pelvic thrusting, anal penetration, and occasionally ejaculation can all be components of this activity. Fellatio or oral-genital activity involves one male licking or sucking on the penis of the other for up to two minutes at a time. This is done in a variety of positions, for example with one male behind the other or mounted on him, sucking his genitals between his legs. The males may even perform mutual fellatio in a 69 position. Males also fondle one another’s scrotum and penis, rubbing the hand up and down the shaft; again, a number of positions are used—one male may stand sideways in front of another who is sitting down, spreading his thighs to allow the seated male to masturbate him, or they may engage in mutual masturbation by backing up toward each other and fondling each other’s genitals between their legs. Sometimes male Stumptails also sit together and masturbate themselves, stimulated by the sight of one another or of a nearby heterosexual mating. The partners in a sexual friendship may be of the same age, or one may be considerably younger than the other, perhaps even an infant.

Female Stumptails also form sexual friendships with one another. These relationships, which involve a considerable amount of affectionate behavior as well, may be a stable association between just two females, or they may be more fluid, involving a network of three females, for example, or more short-lived pairings. Sexual behavior involves mounting with intense genital stimulation and orgasm. One female will climb onto the back of her favorite partner, using a position slightly different from heterosexual mating that allows her to rub her genitals against the rump of the other female. This may also be accomplished in a front-to-back sitting position, one female pulling the other up against her belly, and the two may even end up lying or leaning back together in this configuration. Lesbian interactions are prolonged, lasting up to two minutes (a duration similar to heterosexual mating), and the females usually make numerous pelvic thrusts comparable to the amount performed by a male in a heterosexual mounting. Orgasm is striking: the mounting female tenses up, first pausing and then showing a number of body spasms; her fur stands on end, and this is combined with a characteristic frowning and round-mouthed facial expression (also found in ejaculating males) and rapid breathing sounds. She also experiences a number of intense uterine contractions lasting for nearly a minute. The female being mounted does not, apparently, have the same sort of orgasmic response, although she is in a state of high sexual arousal, and will often reach back to clutch the mounting female and even kiss her during the climax. Following orgasm, the females usually hug one another and make teeth-chattering or squeaking sounds. In some cases females can apparently reach orgasm without direct genital stimulation, particularly when they are hugging their favorite female partner in great excitement after being reunited.

Frequency: Homosexual activity is common in Stumptail Macaques, accounting for as much as 25–40 percent of all sexual encounters in some captive and semi-wild groups. In one study, nearly two-thirds of this same-sex activity was between females, while in another population, all same-sex mounting was between males.

Orientation: Most Stumptail females are probably simultaneously bisexual, interspersing heterosexual activity with homosexual activity. In fact, females have been known to participate in lesbian activities when they are lactating (and possibly even during pregnancy), indicating an easy compatibility between motherhood and homosexuality in this species. Some males show a decrease in the intensity of their same-sex friendships as they get older and may begin engaging in a larger proportion of heterosexual activity as they mature. Nevertheless, most males probably continue to have some homosexual contact throughout their lives.

Male Stumptails engage in both masturbation and nonreproductive heterosexual mating. In the latter case, males have been observed mounting females without full penetration, mating with menstruating females, rubbing their genitals on the female (sometimes to ejaculation), and even stimulating the penis with their own foot while mounted on the female. Both male and female orgasm can be a component of heterosexual mating. Sometimes, however, mating is distinctly less pleasurable—especially for the female, who may collapse under the weight of the male during copulation (he may be up to twice as heavy as she is). Females are also sometimes bitten by males during mounting, resulting in shallow cuts on her shoulders and upper arms (this occurs in about 15–18 percent of copulations). More than half of all matings involve male aggression (including chasing the female, pushing or pulling her, and fighting or biting her) and/or female resistance (including running away from the male, screaming, trying to dislodge him, and fighting with him). In addition, heterosexual copulations are often harassed by other individuals (of both sexes), sometimes in spectacular outbursts of activity that involve an entire social group. This often occurs following ejaculation while the two mating animals remain attached in a “copulatory tie,” similar to that of mating Dogs.

*asterisked references discuss homosexuality/transgender

*Bernstein, I. S. (1980) “Activity Patterns in a Stumptail Macaque Group (Macaca arctoides).” Folia Primatologica 33:20–45.

*Bertrand, M. (1969) The Behavioral Repertoire of the Stumptail Macaque: A Descriptive and Comparative Study. Bibliotheca Primatologica 11. Basel: S. Karger.

*Chevalier-Skolnikoff, S. (1976) “Homosexual Behavior in a Laboratory Group of Stumptail Monkeys (Macaca arctoides): Forms, Contexts, and Possible Social Functions.” Archives of Sexual Behavior 5:511–27.

*———(1974) “Male-Female, Female-Female, and Male-Male Sexual Behavior in the Stumptail Monkey, with Special Attention to the Female Orgasm.” Archives of Sexual Behavior 3:95–116.

*Estrada, A., and R. Estrada (1978) “Changes in Social Structure and Interactions After the Introduction of a Second Group in a Free-ranging Troop of Stumptail Macaques (Macaca arctoides): Social Relations II.” Primates 19:665–80.

*Estrada, A., R. Estrada, and F. Ervin (1977) “Establishment of a Free-ranging Colony of Stumptail Macaques (Macaca arctoides): Social Relations I.” Primates 18:647–76.

*Goldfoot, D. A., H. Westerborg-van Loon, W. Groeneveld, and A. K. Slob (1980) “Behavioral and Physiological Evidence of Sexual Climax in the Female Stump-tailed Macaque (Macaca arctoides).” Science 208:1477–79.

Gouzoules, H. (1974) “Harassment of Sexual Behavior in the Stumptail Macaque, Macaca arctoides.” Folia Primatologica 22:208–17.

*Leinonen, L., I. Linnankoski, M.-L. Laakso, and R. Aulanko (1991) “Vocal Communication Between Species: Man and Macaque.” Language and Communication 11:241–62.

*Linnankoski, I., and L. M. Leinonen (1985) “Compatibility of Male and Female Sexual Behavior in Macaca arctoides.” Zeitschrift für Tierpsychologie 70:115–22.

Niemeyer, C. L., and A. S. Chamove (1983) “Motivation of Harassment of Matings in Stumptailed Macaques.” Behavior 87:298–323.

*O’Keefe, R. T., and K. Lifshitz (1985) “A Behavioral Profile for Stumptail Macaques (Macaca arctoides).” Primates 26:143–60.

*Slob, A. K., and P. E. Schenk (1986) “Heterosexual Experience and Isosexual Behavior in Laboratory-Housed Male Stump-tailed Macaques (M. arctoides).” Archives of Sexual Behavior 15:261–68.

*de Waal, F. B. M. (1989) Peacemaking Among Primates. Cambridge, Mass.: Harvard University Press.

de Waal, F. B. M., and R. Ren (1988) “Comparison of the Reconciliation Behavior of Stumptail and Rhesus Macaques.” Ethology 78:129–42.

Both Bonnet and Crab-eating Macaques live in fairly large matriarchal groups containing numerous adult males and females as well as youngsters; males typically emigrate from their home group on becoming adults. Bonnet groups can be as large as 50–60 monkeys, but most average around 18–20 individuals, with four or five each of adult males and females. Male Bonnets demonstrate a strong tendency to interact and cooperate with one another, often forming supportive COALITIONS together. Crab-eating Macaques live in troops containing 40–50 individuals on average; smaller groups each contain 2–9 adult males. Large subgroups of youngsters, as well as some peripheral or solitary animals, also occur.

Behavioral Expression: Male Bonnet Macaques frequently mount one another, using the same front-to-back position found in heterosexual copulation. A male may have anywhere from two to five different partners that he mounts; each male also varies in the proportion of times he mounts or is mounted. One male acted as the mountee in only 9 percent of his homosexual mountings, another did so in all of his mountings, though the average is a roughly equal proportion of mounter-mountee behavior, and reciprocal mounting occurs as well. In addition, male Bonnets engage in a wide variety of other same-sex behaviors, both affectionate and sexual, often within a coalition “bond” between them. Masturbation of another male is common in all age groups, especially younger males—one male holds or fondles the other’s penis and may even eat the semen from the resulting ejaculation (mutual masturbation also occurs). Males also sometimes grip and gently tug on each other’s scrotum; often, this is accompanied by embracing, nuzzling, grasping of the rump, tongue-clicking, and mouthing of the other’s neck or shoulders, all combined into a sort of ritualized “greeting” interaction. Another behavior, unique to homosexual interactions, involves two males rhythmically rubbing their rumps and genital areas together, often reaching back between their legs to fondle each other’s genitals. This behavior also occurs between females, as does mounting.

Homosexual mounting also occurs in male Crab-eating Macaques. In addition, male Crab-eaters may mouth and fondle the genitals and anal region of another male, including using their index finger to investigate the area. Males can also develop intense sexual friendships with one another, especially between older and younger males. In one such pair observed in captivity, affectionate embraces frequently led to sexual arousal and homosexual mounting, often accompanied by excited lip-smacking or crooning sounds; the male being mounted sometimes even turned his head to kiss his partner during a mount. Both consensual and nonconsensual mounting occurs in Crab-eating Macaques—in the former (54 percent of mounts between males), the mounted animal fully cooperates by standing still and helps support the weight of the other male (and perhaps even initiates the encounter). In nonconsensual mounts (46 percent of mounts between males), the mounting animal may corner his partner and hold him down (this also occurs in heterosexual mounting). Male Crab-eaters also occasionally engage in homosexual contact with other species. Wild Crab-eating Macaques sometimes allow male Orang-utans to perform fellatio on them, while in captivity they have been known to attempt copulation with males of a number of nonprimate species, including foxes.

Frequency: Homosexual mounting is very common in male Bonnet Macaques. In some populations, same-sex mounts exceed the number of heterosexual mounts by as much as four to one, and mounting between males can comprise 31 percent to 79 percent of all mounting. Sexual and affectionate behaviors between males occur in about a quarter of their interactions with one another. Female homosexual activity is somewhat less common: one study found that mounting between females occurred at rates that were two to seven times less than male-female or male-male mounting, although the rates of mutual rump rubbing with genital stimulation between females were only slightly less than between males. In Crab-eating Macaques, homosexual mounting accounts for 17–30 percent of mountings, and 10 percent of all interactions between males involve mounting (compared to nearly 50 percent of all interactions between males and females).

Orientation: Nearly all male Bonnet Macaques participate in both homosexual and heterosexual mounting, but it appears that they generally have more different male partners than female ones. Some males participate very little in homosexual activity (accounting for about 10 percent of the same-sex mountings in a population), while others may be involved in more than half of all homosexual mounts. A similar variation occurs with respect to their heterosexual participation. However, males that are the least active heterosexually are not necessarily the most active homosexually: in many cases, those males that participate in a large number of homosexual mountings also have a large number of heterosexual mountings. No quantitative information on sexual orientation is available for Crab-eaters; however, observations in captivity indicate that males engage in both homosexual and heterosexual copulation, sometimes alternating relatively frequently between the two. Furthermore, males that are “bonded” to one another show a preference for their partner that even survives separation and intervening heterosexual activity. If such males are separated from one another, they rush to embrace each other on being reunited, resuming their sexual relationship where they left off.

As noted above, heterosexual matings in Crab-eating Macaques are not always consensual: about 19 percent of such mounts are forced by the male on the female. Furthermore, male Crab-eaters sometimes severely attack females with small babies and also occasionally kill those infants to gain sexual and breeding access to the female. Both Bonnets and Crab-eaters participate in a range of nonprocreative sexual behaviors. Among Crab-eaters, females copulate during pregnancy (though usually not during the first two to three weeks), while more than half of male-female copulations do not involve ejaculation. In both species, females have multiple male partners and copulations—during one six-month period, for example, each female Crab-eater mated an average of 45 times, with some copulating more than 110 times. Female Bonnets may mate with up to three different males in succession, and females also sometimes mount males (REVERSE mounting). Male Bonnet Macaques may also manually penetrate females, inserting a finger and then licking or smelling it. Unlike in a number of other primates, in Bonnets this behavior does not appear to be simply a way of testing the sexual receptivity of the female. Both male and female Bonnets also masturbate, females sometimes employing innovative techniques (such as using objects or pulling their tail between their legs and using it to rub their labia while making pelvic thrusting movements). Crab-eating Macaques engage in an interesting form of “infidelity”: heterosexual mating typically occurs within a short-term bond or consortship. However, nearly 20 percent of all copulations in some populations are nonmonogamous: half of all females and almost three-quarters of the males “steal” matings with other partners during a consortship, but return to their original partner afterward. The social system of Bonnet Macaques may entail considerable inbreeding, and incestuous mother-son matings that produce viable offspring do occur.

*asterisked references discuss homosexuality/transgender

*Bernstein, S. (1970) “Primate Status Hierarchies.” In L. A. Rosenblum, ed., Primate Behavior: Developments in Field and Laboratory Research, vol. 1, pp. 71–109. New York: Academic Press.

Emory, G. R., and S. J. Harris (1978) “On the Directional Orientation of Female Presents in Macaca fascicularis.” Primates 19:227–29.

*Hamilton, G. V. (1914) “A Study of Sexual Tendencies in Monkeys and Baboons.” Journal of Animal Behavior 4:295–318.

*Kaufman, I. C., and L. A. Rosenblum (1966) “A Behavioral Taxonomy for Macaca nemestrina and Macaca radiata: Based on Longitudinal Observation of Family Groups in the Laboratory.” Primates 7:205–58.

*Makwana, S. C. (1980) “Observations on Population and Behavior of the Bonnet Monkey, Macaca radiata.” Comparative Physiology and Ecology 5:9–12.

Moore, J., and R. Ali (1984) “Are Dispersal and Inbreeding Avoidance Related?” Animal Behavior 32:94–112.

*Nolte, A. (1955) “Field Observations on the Daily Routine and Social Behavior of Common Indian Monkeys, with Special Reference to the Bonnet Monkey (Macaca radiata Geoffroy).” Journal of the Bombay Natural History Society 53:177–84.

Noordwijk, M. A. van (1985) “Sexual Behavior of Sumatran Long-tailed Macaques (Macaca fascicularis).” Zeitschrift für Tierpsychologie 70:277–96.

*Poirier, F. E., and E. O. Smith (1974) “The Crab-Eating Macaques (Macaca fascicularis) of Angaur Island, Palau, Micronesia.” Folia Primatologica 22:258–306.

Rahaman, H., and M. D. Parthasarathy (1969) “Studies on the Social Behavior of Bonnet Monkeys.” Primates 10:149–62.

*———(1968) “The Expressive Movements of the Bonnet Macaque.” Primates 9:259–72.

*Rasmussen, D. R. (1984) “Functional Alterations in the Social Organization of Bonnet Macaques (Macaca radiata) Induced by Ovariectomy: An Experimental Analysis.” Psychoneuroendocrinology 9:343–74.

*Silk, J. B. (1994) “Social Relationships of Male Bonnet Macaques: Male Bonding in a Matrilineal Society.” Behavior 130:271–92.

———(1993) “Does Participation in Coalitions Influence Dominance Relationships Among Male Bonnet Macaques?” Behavior 126:171–89.

Sinha, A. (1997) “Complex Tool Manufacture by a Wild Bonnet Macaque, Macaca radiata.” Folia Primatologica 68:23–25.

*Simonds, P. E. (1996) Personal communication.

*———(1965) “The Bonnet Macaque in South India.” In I. DeVore, ed., Primate Behavior: Field Studies of Monkeys and Apes, pp. 175–96. New York: Holt, Rinehart, & Winston.

*Sugiyama, Y. (1971) “Characteristics of the Social Life of Bonnet Macaques (Macaca radiata).” Primates 12:247–66.

*Thompson, N. S. (1969) “The Motivations Underlying Social Structure in Macaca irus.” Animal Behavior 17:459–67.

*———(1967) “Some Variables Affecting the Behavior of Irus Macaques in Dyadic Encounters.” Animal Behavior 15:307–11.

Both of these species live in cosexual groups, containing 15–40 individuals in Pigtails and up to 40–90 individuals in Crested Black Macaques. Pig-tailed groups are matrilineal clans, in which females remain in their home (natal) group while males emigrate on reaching maturity. The heterosexual mating system is promiscuous: both sexes mate with multiple partners. Smaller Crested Black Macaque groups (6–15 individuals) may contain only one adult male.

Behavioral Expression: Pig-tailed Macaques engage in homosexual mounting as well as kissing. Male Pigtails mount each other using the posture found in heterosexual mating (one male behind the other, hands grasping the loins, and feet clasping the calves of the other), sometimes with erection of the penis and pelvic thrusting (though anal penetration does not occur). Females use the same position and also occasionally thrust against their female partner; the mounting female is usually in heat. Some Pigtails engage in same-sex mounting with only one partner, while other Pigtails have several partners (as many as seven for females, though the average is three). Individuals differ as to whether they prefer mounting or being mounted in homosexual encounters: a few animals engage in only one or the other, while most exhibit a range of mounter/mountee behavior. Males may even mount each other reciprocally, exchanging positions in different mounting sessions. Same-sex kissing (mouth-to-mouth contact) occurs more often than heterosexual kissing and is most common between females. However, many female homosexual mounts are “forced” in the sense that the animal being mounted does not solicit the mounting, and aggression may also be involved: 48 percent of mounts between females are nonconsensual, compared to 18 percent of heterosexual ones. No mounts between males are forced. Some same-sex mounting is incestuous, e.g., between mother and daughter or siblings of either sex.

Crested Black Macaques also participate in male and female homosexual mounting, similar in many ways to that found in Pigtails. Females often reach back to clasp the leg of a female mounting them, which is believed to be a sign of orgasm (it also occurs in heterosexual mounting), while males being mounted by other males frequently fondle their own penis. Mounting is sometimes preceded by a gesture of invitation known as REAR-END FLIRTATION, in which one male walks by another and presents his hindquarters. Younger males often mount older ones in this species. A number of other homosexual activities occur in Crested Black Macaques. Females engage in a form of mutual masturbation unique to homosexual interactions, in which they stand side by side facing in opposite directions (draping an arm over the other’s waist) and fondle and sniff each other’s vulva, sometimes with direct clitoral stimulation. Males often participate in a form of erotic grooming: one male uses his hands, lips, and tongue to groom the other, who usually has an erection and may masturbate himself by rolling his penis between his palms or licking it (he usually eats his own semen if he ejaculates). The grooming animal is often sexually aroused, too, as evidenced by his erection. Males (especially younger ones) also use a number of ritualized erotic “greeting” gestures with one another, including embracing, face-licking or kissing, fondling or grabbing of the erect penis, mounting, and rump fingering.

Frequency: Same-sex mounting occurs frequently in Pig-tailed Macaques, accounting for 7–23 percent of all mounting activity. More than three-quarters of all kissing occurs between females. In Crested Black Macaques, about 5–8 percent of all mounting activity occurs between males. Ritualized penis-grabbing or fondling between males takes place regularly in this species and can be observed weekly, and perhaps even daily, in some wild populations.

Orientation: Most Pig-tailed Macaques are probably bisexual, engaging in both same- and opposite-sex mounting. However, individuals vary along a continuum of what percentage of their activity is homosexual: for some males, it is as little as 8 percent, while for others, nearly two-thirds of their mounting activity is same-sex. Although less specific information is available for Crested Black Macaques, they appear to have a similar orientation profile: in one wild troop, for example, all males participated in both heterosexual and homosexual mounting (as well as penis-grabbing) to varying degrees.

As noted above, some heterosexual copulations in Pig-tailed Macaques are forced, in that the female is an unwilling participant. Furthermore, more than a third of aggressive interactions in Pigtails are between males and females (73 percent are directed by the male against the female). Infanticide has also been seen among captive Pigtails—in some cases, infants as young as one day old have died from head and neck injuries inflicted by adult males. In addition, a 33—year study of this species (spanning seven generations and nearly 400 individuals) found that one in eight infants is physically abused or neglected by its mother. This includes being dragged across the ground, having its fingers or tail chewed, suffering severe eye damage or blindness as a result of compulsive grooming around the eyes, having its head or body crushed on the ground, and/or being rejected, abandoned, or starved by its mother. Physical abuse accounts for about a third of all Pigtail infant injuries or deaths; it appears to run in families and is usually repeated with successive offspring. Infants can also be injured when they are kidnapped, which occurs only occasionally and is typically carried out by a nonbreeding female.

A number of nonreproductive sexual behaviors occur in these two species as well. In Pigtails, males mount nonovulating females 8—15 percent of the time, and 1—2 percent of heterosexual behavior involves females mounting males (REVERSE mounts). In addition, female Pigtails may mate with up to five different males during a single period of heat. Mother-son mountings occur as well. In both of these species, heterosexual mounting sometimes does not involve penetration: nearly a fifth of Crested Black male-female mounts, for example, are “ritualized” or non-copulatory. Male Pigtails and Crested Black Macaques also masturbate, occasionally eating their own semen, while female Crested Black Macaques sometimes masturbate by inserting a finger into the vagina and simultaneously slapping their rump with one hand. Infant and very young male Crested Blacks often mount adult females, performing pelvic thrusts and even achieving penetration. Finally, spontaneous abortions occur among Pigtails, often associated with a number of physiological changes in the female’s blood chemistry: one study in captivity found that 14 percent of pregnancies terminated in abortions (among females not otherwise at high risk for miscarriages).

Homosexual mounting occurs in three other species of Macaques: Lion-tailed (Macaca silenus), Tonkean (Macaca tonkeana), and Moor (Macaca maurus) Macaques. In the latter two species, 11—13 percent of mounting activity is same-sex.

*asterisked references discuss homosexuality/transgender

*Bernstein, I. S. (1972) “Daily Activity Cycles and Weather Influences on a Pigtail Monkey Group.” Folia Primatologica 18:390-415.

*———(1970) “Primate Status Hierarchies.” In L. A. Rosenblum, ed., Primate Behavior: Developments in Field and Laboratory Research, vol.1, pp. 71—109. New York: Academic Press.

*———(1967) “A Field Study of the Pigtail Macaque (Macaca nemestrina).” Primates 8:217-28.

Bernstein, I. S., and S. C. Baker (1988) “Activity Patterns in a Captive Group of Celebes BlackApes (Macaca nigra).” Folia Primatologica 51:61-75.

*Bound, V., H. Shewman, and J. Sievert (1988) “The Successful Introduction of Five Male Lion-tailed Macaques (Macaca silenus) at Woodland Park Zoo.” In AAZPA Regional Conference Proceedings, pp. 122-31. Wheeling, W.Va.: American Association of Zoological Parks and Aquariums.

*Caldecott, J. 0. (1986) An Ecological and Behavioral Study of the Pig-Tailed Macaque. Basel: Karger.

*Dixson, A. F. (1977) “Observations of the Displays, Menstrual Cycles, and Sexual Behavior of the ‘Black Ape’ of Celebes (Macaca nigra).” Journal of Zoology, London 182:63-84.

*Giacoma, C., and P. Messeri (1992) “Attributes and Validity of Dominance Hierarchy in the Female Pigtail Macaque.” Primates 33:181-89.

*Kaufman, I. C., and L. A. Rosenblum (1966) “A Behavioral Taxonomy for Macaca nemestrina and Macaca radiata: Based on Longitudinal Observation of Family Groups in the Laboratory.” Primates 7:205—58.

Kyes, R. C., R. E. Rumawas, E. Sulistiawati, and N. Budiarsa (1995) “Infanticide in a Captive Group of Pigtailed Macaques (Macaca nemestrina):” American Journal of Primatology 36:135-36.

Maestripieri, D., K. Wallen, and K. A. Carroll (1997) “Infant Abuse Runs in Families of Group-Living Pigtail Macaques.” Child Abuse e’r Neglect 21:465—71.

*Matsumura, S., and K. Okamoto (1998) “Frequent Harassment of Mounting After a Takeover of a Group of Moor Macaques (Macaca maurus).” Primates 39:225—30.

*Nickelson, S. A., and J. S. Lockard (1978) “Ethogram of Celebes Monkeys (Macaca nigra) in Two Captive Habitats.” Primates 19:437—47.

Oi, T. (1996) “Sexual Behavior and Mating System of the Wild Pig-tailed Macaque in West Sumatra.” In J. E. Fa and D. G. Lindburg, eds., Evolution and Ecology of Macaque Societies, pp. 342—68. Cambridge: Cambridge University Press.

*———(1991) “Non-copulatory Mounting of Wild Pig-tailed Macaques (Macaca nemestrina nemestrina) in West Sumatra, Indonesia.” In A. Ehara, T. Kimura, O. Takenaka, and M. Iwamoto, eds., Primatology Today, pp. 147—50. Amsterdam: Elsevier Science Publishers.

*———(1990a) “Patterns of Dominance and Affiliation in Wild Pig-tailed Macaques (Macaca nemestrina nemestrina) in West Sumatra.” International Journal of Primatology 11:339—55.

———(1990b) “Population Organization of Wild Pig-tailed Macaques (Macaca nemestrina nemestrina) in West Sumatra.” Primates 31:15—31.

*Poirier, F. E. (1964) “The Communicative Matrix of the Celebes Ape (Cynopithecus niger): A Study of Sixteen Male Laboratory Animals.” Master’s thesis, University of Oregon.

*Reed, C. (1997) Personal communication.

*Reed, C., T. G. O’Brien, and M. F. Kinnaird (1997) “Male Social Behavior and Dominance Hierarchy in the Sulawesi Crested Black Macaque (Macaca nigra).” International Journal of Primatology 18:247—60.

Schiller, H. S., G. P. Sackett, W. T. Frederickson, and L. J. Risler (1983) “Maintenance of High-density Lipoprotein Blood Levels Prior to Spontaneous Abortion in Pig-tailed Macaques (Macaca nemestrina).” American Journal of Primatology 4:127—33.

*Skinner, S. W, and J. S. Lochard (1979) “An Ethogram of the Liontail Macaque (Macaca silenus) in Captivity.” Applied Animal Ethology 5:241-53.

*Thierry, B. (1986) “Affiliative Interference in Mounts in a Group of Tonkean Macaques (Macaca tonkeana).” American Journal of Primatology 11:89—97.

*Tokuda, K., R. C. Simons, and G. D. Jensen (1968) “Sexual Behavior in a Captive Group of Pigtailed Monkeys (Macaca nemestrina).” Primates 9:283—94.

OTHER PRIMATES

Savanna Baboons live in groups of 30—100 containing both adult males and females. Females form the matriarchal core of each group since they remain for life, whereas males often emigrate to a new group on reaching adulthood. However, some troops are strongly inbred because individuals rarely leave. In contrast, both Gelada and Hamadryas Baboons live in large troops that include so-called HAREM groups—bands that have a single male and several females. In Geladas, the primary social bonds are between the females in such groups (most of whom are related to each other, as in Savanna Baboons), whereas in Hamadryas Baboons the primary bonds are between the male and the females. Unlike many other primates, Hamadryas females emigrate from the group while males remain (hence, most of the females in a group are not related to each other). Geladas also have “bachelor” troops of nonbreeding males, and “bachelor” Hamadryas or Gelada males sometimes associate with a harem group and may develop a close relationship with its male leader.

Behavioral Expression: Homosexual mounting among both males and females occurs in all three of these Baboon species. The position used is similar to that for heterosexual copulation: the mounting animal places its hands on the mountee’s lower back and clasps the mountee’s ankles or thighs with its feet. Both sexes often make pelvic thrusts during homosexual mounts; males usually have an erection, and ejaculation does occur in at least some Savanna Baboon mounts between males. Male Savanna Baboons also sometimes fondle their own or their partner’s genitals during a same-sex mount, and male mounters may gently bite or nuzzle their partner’s neck after a homosexual mount. Male Geladas have also been observed masturbating other males. Females of these species mount each other both during “heat” and outside of their sexual cycle; about 9 percent of lesbian mounts in Savanna Baboons involve a pregnant female mounting another female. Because most Savanna and Gelada females are related to the other females in a troop, at least some homosexual activity is incestuous.

In Savanna Baboons, homosexual mounting occurs in a variety of contexts, including during good-natured play-fighting. However, in this species (and to some extent also in the other species) same-sex mounting is most prominent as part of a unique form of male “greeting” interaction. Whenever two males meet each other, they exchange a series of ritualized sexual behaviors that may include homosexual mounting and invitations to mount, as well as a wide variety of other sexual and affectionate contacts. One such behavior is known as DIDDLING, in which the males fondle each other’s genitals, including touching or pulling on the penis and fondling the scrotum. Males also embrace and kiss each other on the head or mouth, and may even bend down to kiss, lick, or nibble on another male’s penis or nuzzle his groin and thighs. Sometimes a male will also nuzzle another male’s back with his nose, especially during a mount. Another “greeting” behavior involves one male patting, grabbing, and sometimes even nuzzling or fingering another male’s rear end. Although most “greeting” interactions are relatively brief and one-sided, occasionally two males develop a closer, bonded relationship sometimes known as a COALITION, in which the “greeting” interactions are more extensive, frequent, and reciprocated. Partners in such an alliance take turns exchanging sexual behaviors with each other (especially diddling), and they often protect and help one another. Such coalitions between males may become stable, long-lasting associations that persist for many years.

Several different kinds of intersexual or hermaphrodite individuals occur spontaneously in Savanna Baboons. In South African populations, gender-mixing individuals sometimes become high-ranking and powerful members of their troops. Such animals have female genitalia and internal organs, yet their mammary glands are not developed. Genetically, they are male (having XY chromosomes), physically they are large—exceeding the proportions of nonintersexed females and sometimes even males—and sexually, they often interact with males. Another type of intersexuality found in Baboons involves animals that have male external genitals (including testes) combined with some female internal reproductive organs (such as a uterus and fallopian tubes).

Frequency: Among Savanna Baboons, homosexual activity is common: 13—24 percent of all mounting behavior is between males and up to 9 percent is between females. “Greetings” interactions—which include ritualized homosexual activities—occur more than twice as often as any other form of interaction between males and take place roughly once every 50 minutes in some troops. Approximately 10 percent of males in some areas develop closely bonded coalitions, which comprise about 2 percent of all dyads between males. In Hamadryas Baboons, sexual behavior (homosexual or heterosexual) is overall less frequent, but approximately one-third to two-thirds of sexual activity may occur between animals of the same sex (mostly between males). In a study of wild Geladas, homosexual interactions between males were observed about once every two hours; in captivity, 14—25 percent of mounts are between males and 2—3 percent are between females.

Orientation: In Savanna Baboons, the entire male population participates in homosexual “greetings” interactions; all adult males (including those in bonded coalitions with other males) are sexually active with females as well, indicating a high degree of bisexuality. This is probably true to a lesser extent for females, not all of whom engage in homosexual mounting. In Hamadryas Baboons, harem-holding males may be bisexual, mounting both males and females, while Gelada harem males are usually exclusively heterosexual (although they may engage in same-sex genital handling if there is another male in the troop). Some “bachelor” males in both species may engage solely in homosexual activity, especially adolescents and younger adults. In Geladas, for example, an average of 12 percent of the population lives in all-male groups (where same-sex activity usually occurs). In some areas this proportion is as high as 40 percent or more, although most such males do eventually breed.

A large proportion of Baboon heterosexual behavior involves nonprocreative activities. Savanna and Hamadryas Baboons commonly mate when the female cannot get pregnant. In some Savanna populations, up to 18 percent of heterosexual copulations occur during the nonfertilizable stages of her ovulatory cycle (including during menstruation) and 2—12 percent of matings happen when the female is already pregnant. Most females, however, remain abstinent while pregnant or lactating and in fact are (hetero)sexually active for less than 10 percent of their adult lives. Heterosexual mountings do not always involve penetration and/or ejaculation, either—in fact, one study found that less than 40 percent of opposite-sex matings in Savanna Baboons involved “full” copulation. Moreover, a variety of sexual behaviors besides vaginal intercourse occur, including fondling of genitals and females mounting males (REVERSE mounts). Masturbation is also a component of Baboon sexual expression, with several innovative techniques employed: Savanna males stimulate the penis with their hand, lick their own penis, rub their genitals against the ground, or stroke the penis with the tip of the tail, while females stimulate the clitoris and perineal area with the tail or fingers. Both males and females show evidence of sexual arousal during grooming, in the form of rhythmic erection of the genitals—“penis flicking” in males, and labial and clitoral swelling and “pulsation” in females. Sexual activity in Baboons also sometimes includes copulation with partners that are not optimal for breeding: adult male Savanna Baboons and adult female Hamadryas Baboons may mate with juvenile animals, incestuous matings are common in inbred troops, while “friendships” and sexual behavior between Baboons and Common Chimpanzees have been observed in the wild (and between female Savanna Baboons and male Macaques in captivity). In addition, infertile females are occasionally found in Savanna Baboons—in one troop they constituted 10 percent of all the adult females—and these individuals continue to engage in sexual behavior.

Several other forms of nonbreeding are found among Baboons. Geladas and Hamadryas Baboons, for example, have significant “bachelor” populations that do not generally participate in reproduction (constituting 20 percent of the male Hamadryas population). Older female Savanna Baboons sometimes experience a postreproductive period, while breeding-age males and females in this species often form platonic “friendships” with each other. Sexual relations in Baboons, however, are sometimes characterized by significant antagonism and even violence between the sexes. Hamadryas harem males often threaten and attack females, biting them on the neck to prevent them from leaving the group. Adult male Savanna Baboons sometimes rape younger females, often seriously injuring them, and adult females avoid or refuse a third of all mating attempts by males. In some populations, abortions and infanticide result when an outside male takes over a troop. He viciously attacks both mothers and infants to maximize his breeding opportunities; as a result of this brutality, females may suffer severe injuries as well as miscarriages, and infants may be killed. There is also evidence that females attack other females in order to suppress their reproduction. Infanticide was recently discovered among Geladas as well. Many male Baboons act as “baby-sitters” for infants, although occasionally the youngsters become injured during fights between their “baby-sitter” (or “kidnapper”) and other males.

Homosexual activity occurs in several other species of African monkeys. Same-sex mounting (in both males and females) is found in Vervets (Cercopithecus aethiops) (comprising about 11 percent of all mounting), Sooty Mangabeys (cercocebus torquatus) (about 18 percent of mounting), and Talapoins (Miopithecus talapoin). Mounting between male Vervets is often accompanied by grooming, embracing from behind, fondling and displaying of the genitals, and nuzzling of the perineum and scrotum. Same-sex mounting in Talapoins may also include embracing or play-wrestling. Among Patas Monkeys (Erythrocebus patas), adolescent and younger males often fondle and nuzzle the scrotum and genitals of adult males.

*asterisked references discuss homosexuality/transgender

*Abegglen, J.-J. (1984) On Socialization in Hamadryas Baboons: A Field Study. Lewisburg, Pa.: Bucknell University Press.

*Bernstein, I. S. (1975) “Activity Patterns in a Gelada Monkey Group.” Folia Primatologica 23:50—71.

*———(1970) “Primate Status Hierarchies.” In L. A. Rosenblum, ed., Primate Behavior: Developments in Field and Laboratory Research, vol.l, pp. 71—109. New York: Academic Press.

*Bielert, C. (1985) “Testosterone Propionate Treatment of an XY Gonadal Dysgenetic Chacma Baboon.” Hormones and Behavior 19:372—85.

*———(1984a) “The Social Interactions of Adult Conspecifics with an Adult XY Gonadal Dysgenetic Chacma Baboon (Papio ursinus).” Hormones and Behavior 18:42-55.

*———(1984b) “Estradiol Benzoate Treatment of an XY Gonadal Dysgenetic Chacma Baboon.” Hormones and Behavior 18:191—205.

*Bielert, C., R. Bernstein, G. B. Simon, and L. A. van der Walt (1980) “XY Gonadal Dysgenesis in a Chacma Baboon (Papio ursinus).” International Journal of Primatology 1:3—14.

*Dixson, A. F., D. M. Scruton, and J. Herbert (1975) “Behavior of the Talapoin Monkey (Miopithecus talapoin) Studied in Groups, in the Laboratory.” Journal of Zoology, London 176:177—210.

Dunbar, R. (1984) Reproductive Decisions: An Economic Analysis of Gelada Baboon Social Strategies. Princeton: Princeton University Press.

*Dunbar, R., and P. Dunbar (1975) Social Dynamics of Gelada Baboons. Basel: S. Karger.

*Fedigan, L. M. (1972) “Roles and Activities of Male Geladas (Theropithecus gelada).” Behavior 41:82-90.

*Gartlan, J. S. (1974) “Adaptive Aspects of Social Structure in Eryhthrocebus patas.” In S. Kondo, M. Kawai, A. Ehara, and S. Kawamura, eds., Proceedings from the Symposia of the Fifth Congress of the International Primatological Society, pp. 161-71. Tokyo: Japan Science Press.

*———(1969) “Sexual and Maternal Behavior of the Vervet Monkey, Cercopithecus aethiops.” Journal of Reproduction and Fertility, supplement 6:137—50.

*Hall, K. R. L. (1962) “The Sexual, Agonistic, and Derived Social Behavior Patterns of the Wild Chacma Baboon, Papio ursinus.” Proceedings of the Zoological Society of London 139:283—327.

*Hausfater, G., and D. Takacs (1987) “Structure and Function of Hindquarter Presentations in Yellow Ba boons (Papio cynocephalus).” Ethology 74:297—319.

*Kummer, H. (1968) Social Organization of Hamadryas Baboons. Chicago: University of Chicago Press.

*Kummer, H., and F. Kurt (1965) “A Comparison of Social Behavior in Captive and Wild Hamadryas Baboons.” In H. Vagtborg, ed., The Baboon in Medical Research, pp. 65—80. Austin: University of Texas Press.

*Leresche, L. A. (1976) “Dyadic Play in Hamadryas Baboons.” Behavior 57:190—205.

*Marais, E. N. (1926) “Baboons, Hypnosis, and Insanity.” Psyche 7:104—10.

*———(1922/1969) The Soul of the Ape. New York: Atheneum.

*Maxim, P. E., and J. Buettner-Janusch (1963) “A Field Study of the Kenya Baboon.” American Journal of Physical Anthropology 21:165—80.

Mori, A., T. Iwamoto, and A. Bekele (1997) “A Case of Infanticide in a Recently Found Gelada Population in Arsi, Ethiopia.” Primates 38:79-88.

*Mori, U. (1979) “Individual Relationships within a Unit; Development of Sociability and Social Status.” In M. Kawai (ed.) Ecological and Sociological Studies of Gelada Baboons, pp. 93-154. Basel: S. Karger.

*Noë, R. (1992) “Alliance Formation Among Male Baboons: Shopping for Profitable Partners.” In A. H. Harcourt and F. B. M. de Waal, eds., Coalitions and Alliances in Humans and Other Animals, pp. 284-321. Oxford: Oxford University Press.

*Owens, N. W. (1976) “The Development of Sociosexual Behaviour in Free-Living Baboons, Papio anubis.” Behavior 57:241—59.

Packer, C. (1980) “Male Care and Exploitation of Infants in Papio anubis.” Animal Behavior 28:512—20.

Pereira, M. E. (1983) “Abortion Following the Immigration of an Adult Male Baboon (Papio cynocephalus).” American Journal of Primatology 4:93—98.

*Ransom, T. W. (1981) Beach Troop of the Gombe. Lewisburg, Pa.: Bucknell University Press; London and Toronto: Associated University Presses.

*Rowell, T. E. (1973) “Social Organization of Wild Talapoin Monkeys.” American Journal of Physical Anthropology 38:593—98.

*———(1967a) “Female Reproductive Cycles and the Behavior of Baboons and Rhesus Macaques.” In S. A. Altmann, ed., Social Communication Among Primates, pp. 15—32. Chicago: University of Chicago Press.

“———(1967b) “A Quantitative Comparison of the Behavior of a Wild and a Caged Baboon Group.” Animal Behavior 15:499—509.

Saayman, G. S. (1970) “The Menstrual Cycle and Sexual Behavior in a Troop of Free Ranging Chacma Baboons (Papio ursinus).” Folia Primatologica 12:81—110.

Smuts, B. B. (1987) “What Are Friends For?” Natural History 96(2):36-45.

———(1985) Sex and Friendship in Baboons. New York: Aldine.

*Smuts, B. B., and J. M. Watanabe (1990) “Social Relationships and Ritualized Greetings in Adult Male Baboons (Papio cynocephalus anubis).” International Journal of Primatology 11:147—72.

*Struhsaker, T. T. (1967) Behavior of Vervet Monkeys (Cercopithecus aethiops). University of California Publications in Zoology, vol. 82. Berkeley: University of California Press.

*Wadsworth, P. F., D. G. Allen, and D. E. Prentice (1978) “Pseudohermaphroditism in a Baboon (Papio anubis).” Toxicology Letters 1:261—66.

Wasser, S. K., and S. K. Starling (1988) “Proximate and Ultimate Causes of Reproductive Suppression Among Female Yellow Baboons at Mikumi National Park, Tanzania.” American Journal of Primatology 16:97—121.

*Weinrich, J. D. (1980) “Homosexual Behavior in Animals: A New Review of Observations From the Wild, and Their Relationship to Human Sexuality.” In R. Forleo and W. Pasini, eds., Medical Sexology: The Third International Congress, pp. 288—95. Littleton, Mass.: PSG Publishing.

*Wolfheim, J. H., and T. E. Rowell (1972) “Communication Among Captive Talapoin Monkeys (Miopithecus talapoin).” Folia Primatologica 18:224—55.

*Zuckerman, S. (1932) The Social Life of Monkeys and Apes. New York: Harcourt, Brace and Company.

Squirrel Monkeys live in troops of 20–70 animals containing a majority of females. Younger males leave their home troops and live for several years in all-male “bachelor” bands of 2–10 monkeys, after which they join the cosexual troops as peripheral members. Females generally remain in their home troops for life, where they develop strong bonds with each other. Rufous-naped Tamarins live in cosexual groups of 3–9 individuals in which usually only one male-female pair breeds; the remainder of the group consists of their offspring and unrelated adult nonbreeders.

Behavioral Expression: Female Squirrel Monkeys court and mount each other. Homosexual courtship is initiated by one female facing the other, tilting her head, and making a “purring” noise (a series of soft, guttural clicklike sounds). This may be accompanied by a GENITAL DISPLAY, in which the soliciting female positions herself in front of the other, spreading her thighs to expose her vulva and engorged or erect clitoris. As an invitation to the other female to mount, she turns around and presents her hindquarters, looking over her shoulder with her feet spread apart. This may be repeated several times, the presenting female moving away each time as the other female approaches in a sort of courtship “chase.” Mounting is done in the same position used for heterosexual mating: one female grasps the other’s waist with her hands and her calves with her feet, making thrusting movements with her pelvis. The mounted female frequently purrs during the sexual interaction. Sometimes two females take turns mounting each other, but often one female is more typically a mounter and the other a mountee.

Female Squirrel Monkeys may develop a short, consortlike bond (also seen in heterosexual interactions) during which they interact sexually with one another. In addition, a number of other types of female bonding occur in this species. Females frequently have one close female “friend” with whom they travel and rest; often this relationship develops into a highly affectionate one and may even include coparenting. The two females frequently touch hands, kiss each other on the mouth, and huddle together. If one of them is a mother, the other helps her raise her infant; if both are mothers, they help each other with parenting, including nuzzling and carrying each other’s infant and protecting them from predators. Often the infant develops a strong bond with the comother, although some females act as coparents for infants belonging to several different mothers. The coparenting female is sometimes known as an “aunt,” although she need not be genetically related to the mother; her relationship with the mother often outlasts the duration of parenting.

Homosexual mounting sometimes occurs between male Squirrel Monkeys, especially younger individuals or between an older and a younger (adult) partner; adult males also perform the genital display to each other. During intense displays, one male will thrust his erect penis into the face of the other male while holding him down with his hands and may even climb onto the back of the other male (who also sometimes develops an erection). Several males can be drawn into the activity, forming a ball or “pileup” of three or four individuals all twisting and climbing on one another as they try to perform genital displays.

In Rufous-naped Tamarins, homosexual behavior takes the form of same-sex mounting, including pelvic thrusting (as in heterosexual copulation); both males and females participate in homosexual mounts.

Frequency: In captivity, homosexual mounting can occur quite frequently in both mixed-sex and single-sex groups of Squirrel Monkeys: one study recorded mounts between females roughly once every 40 minutes, with homosexual activity taking place over three to seven days each month. An average of about 40 percent of genital displays occur between animals of the same sex; more than one-quarter are between females. In Rufous-naped Tamarins, homosexual mounting occurs sporadically.

Orientation: Some female Squirrel Monkeys that bond with other females as coparents are themselves nonbreeders; to this extent, then, they are involved exclusively in same-sex activities. Most other Squirrel Monkeys, as well as Rufous-naped Tamarins, that participate in homosexual behavior are probably simultaneously bisexual. In a group of three Squirrel Monkeys (two females and one male) whose sexual activities were briefly sampled, for example, heterosexual and homosexual encounters alternated continuously for a half hour, and more than 25 percent of the courtship and sexual activities were between the females. However, no detailed long-term studies have been conducted to verify the extent of individuals’ same-sex versus opposite-sex activity throughout their entire lives.

In addition to the female coparenting arrangement described above, other alternative family configurations and nonbreeding individuals occur in Squirrel Monkeys. One female sometimes adopts another female’s infant, raising it along with her own baby, while some male Squirrel Monkeys never copulate at all during the mating season. Interestingly, these may be the highest-ranking males in the troop, who are often more aggressive and less patient than other males and therefore more likely to disturb females or fail to attract willing mates. Several other aspects of Squirrel Monkey heterosexual life reveal considerable antagonism and separation between the sexes. Females often form groups or COALITIONS during the mating season to chase off males who are pursuing unwilling females; females (and occasionally males) may also directly disrupt heterosexual copulations in progress. At other times, females persistently harass males so that they remain spatially segregated from the females, either on the periphery of the troop or closer to the ground. When a willing female is found and the sexual interaction is not disturbed, often several males will participate, all joining in by kissing the female on the mouth, displaying their genitals, and sniffing or nuzzling her genitalia. The mating system is promiscuous, as both males and females copulate with multiple partners.

A number of nonprocreative sexual activities are also found in these New World monkeys. Male Squirrel Monkeys masturbate by either sucking their own penis or rubbing it with one or both hands, while females may copulate when not in heat or during pregnancy (up to the fourth month). In addition, females sometimes produce a vulvar plug from sloughed vaginal cells when they are in heat, which may serve to limit inseminations. Rufous-naped Tamarin males on occasion mount females without thrusting or penetration. Male Squirrel Monkeys also have a pronounced sexual cycle: for three to four months out of the year, they are sexually active, more aggressive, and develop a characteriscic appearance—heavier, with more fluffed fur—during which time they are known as FATTED MALES. For the remainder of the year, however, their testes are essentially dormant; they lose their “fatted” appearance and live largely separate from the females. In Rufous-naped Tamarins, as in other tamarins and marmosets, all but the highest-ranking female in a group forgo reproduction, perhaps through a complex mechanism of “self-restraint” that is mediated by pheromones from the lead female. As a result, only about half of all mature females actually reproduce at one time; however, nonbreeding individuals often continue to copulate. In addition, most matings outside the breeding season do not result in offspring, and it is thought that many embryos may be reabsorbed, aborted, or the young die soon after birth.

Same-sex activity occurs in several other species of Central and South American monkeys. Homosexual mounting (in both males and females), including pelvic thrusting and genital rubbing on the partner, has been observed in a variety of Tamarin species, including the Saddle-back Tamarin (Saguinus fuscicollis), the Mustached Tamarin (S. mystax), and the Cotton-top Tamarin (S. oedipus). Both male and female Lion Tamarins (Leontopithecus rosalia) sometimes mount their own offspring of both sexes, including adolescents and younger individuals. Approximately 1 percent of mounting activity in Common Marmosets (Callithrix jac-chus) occurs among adolescent and younger males (brothers living in the same family group). In White-fronted Capuchin Monkeys (Cebus albifrons), young males occasionally suck and fondle the scrotum of older males, while homosexual activity among females (including mounting) also occurs in Brown Capuchins (C. apella) and Weeper Capuchins (C. olivaceous). More than half of all mounting in White-faced Capuchins (C. capucinus) is between same-sex partners, often preceded by a type of courtship activity known as WHEEZE DANCING, involving contorted postures, wheezing vocalizations, and “slow-motion” chases.

*asterisked references discuss homosexualityltransgender

*Akers, J. S., and C. H. Conaway (1979) “Female Homosexual Behavior in Macaca mulatta.” Archives of Sexual Behavior 8:63—80.

*Anschel, S., and G. Talmage-Riggs (1978) “Social Structure Dynamics in Small Groups of Captive Squirrel Monkeys.” In D. J. Chivers and J. Herbert, eds., Recent Advances in Primatology, vol. 1, pp. 601—4. New York: Academic Press.

*Baldwin, J. D. (1969) “The Ontogeny of Social Behavior of Squirrel Monkeys (Saimiri sciureus) in a Seminatural Environment.” Folia Primatologica 11:35—79.

———(1968) “The Social Behavior of Adult Male Squirrel Monkeys (Saimiri sciureus) in a Seminatural Environment.” Folia Primatologica 9:281—314.

Baldwin, J. D., and J. I. Baldwin (1981) “The Squirrel Monkeys, Genus Saimiri.” In A. F. Coimbra-Filho and R. A. Mittermeier, eds., Ecology and Behavior of Neotropical Primates, vol. 1, pp. 277—330. Rio de Janeiro: Academia Brasileira de Ciencias.

*Castell, R., and B. Heinrich (1971) “Rank Order in a Captive Female Squirrel Monkey Colony.” Folia Primatologica 14:182—89.

Dawson, G. A. (1976) “Behavioral Ecology of the Panamanian Tamarin, Saguinus oedipus (Callitrichidae, Primates).” Ph.D. thesis, Michigan State University.

*Defler, T. R. (1979) “On the Ecology and Behavior of Cebus albifrons in Eastern Colombia: II. Behavior.” Primates 20:491—502.

*Denniston, R. H. (1980) “Ambisexuality in Animals.” In J. Marmor, ed., Homosexual Behavior: A Modern Reappraisal, pp. 25—40. New York: Basic Books.

*DuMond, F. V. (1968) “The Squirrel Monkey in a Seminatural Environment.” In L. A. Rosenblum and R. W. Cooper, eds., The Squirrel Monkey, pp. 87-145. New York: Academic Press.

DuMond, F. V., and T. C. Hutchinson (1967) “Squirrel Monkey Reproduction: The ‘Fatted’ Male Phenomenon and Seasonal Spermatogenesis.” Science 158:1067—70.

*Hoage, R. J. (1982) Social and Physical Maturation in Captive Lion Tamarins, Leontopithecus rosalia rosalia (Primates: Callitrichidae). Smithsonian Contributions to Zoology no. 354. Washington, D.C.: Smithsonian Institution Press.

Hopf, S., E. Hartmann-Wiesner, B. Kuhlmorgen, and S. Mayer (1974) “The Behavioral Repertoire of the Squirrel Monkey (Saimiri).” Folia Primatologica 21:225—49.

Latta, J., S. Hopf, and D. Ploog (1967) “Observation of Mating Behavior and Sexual Play in the Squirrel Monkey (Saimiri sciureus).” Primates 8:229—46.

*Linn, G. S., D. Mase, D. LaFrançois, R. T. O’Keeffe, and K. Lifshitz (1995) “Social and Menstrual Cycle Phase Influences on the Behavior of Group-Housed Cebus apella.” American Journal of Primatology 35:41—57.

*Manson, J. H., S. Perry, and A. R. Parish (1997) “Nonconceptive Sexual Behavior in Bonobos and Capuchins.” International Journal of Primatology 18:767-86.

*Mendoza, S. P., and W. A. Mason (1991) “Breeding Readiness in Squirrel Monkeys: Female-Primed Females are Triggered by Males.” Physiology & Behavior 49:471—79.

Mitchell, C. L. (1994) “Migration Alliances and Coalitions Among Adult Male South American Squirrel Monkeys (Saimiri sciureus).” Behavior 130:169—90.

*Moynihan, M. (1970) Some Behavior Patterns of Platyrrhine Monkeys. II. Saguinus geoffroyi and Some Other Tamarins. Smithsonian Contributions to Zoology no. 28. Washington, D.C.: Smithsonian Institution Press.

*Perry, S. (1998) “Male-Male Social Relationships in Wild White-faced Capuchins, Cebus capucinus.” Behavior 135:139—72.

Peters, M. (1970) “Mouth to Mouth Contact in Squirrel Monkeys (Saimiri sciureus).” Zeitschrift für Tierpsychologie 27:1009—10.

Ploog, D. W (1967) “The Behavior of Squirrel Monkeys (Saimiri sciureus) as Revealed by Sociometry, Bioa-coustics, and Brain Stimulation.” In S. Altmann, ed., Social Communication Among Primates, pp. 149— 84. Chicago: University of Chicago Press.

*Ploog, D. W., J. Blitz, and F. Ploog (1963) “Studies on the Social and Sexual Behavior of the Squirrel Monkey (Saimiri sciureus).” Folia Primatologica 1:29—66.

Ploog, D. W., and P. D. Maclean (1963) “Display of Penile Erection in Squirrel Monkey (Saimiri sciureus).” Animal Behavior 11:32—39.

Rosenblum, L.A. (1968) “Mother-Infant Relations and Early Behavioral Development in the Squirrel Monkey.” In L. A. Rosenblum and R. W. Cooper, eds., The Squirrel Monkey, pp. 207—33. New York: Academic Press.

*Rothe, H. (1975) “Some Aspects of Sexuality and Reproduction in Groups of Captive Marmosets (Callithrix jacchus).” Zeitschrift für Tierpsychologie 37:255-73.

*Shadle, A. R., E. A. Mirand, and J. T. Grace Jr. (1965) “Breeding Responses in Tamarins.” Laboratory Animal Care 15:1—10.

Skinner, C. (1985) “A Field Study of Geoffroy’s Tamarin (Saguinus geoffroyi) in Panama.” American Journal of Primatology 9:15—25.

Snowdon, C. T. (1996) “Infant Care in Cooperatively Breeding Species.” Advances in the Study of Behavior 25:643—89.

Srivastava, P. K., F. Cavazos, and F. V. Lucas (1970) “Biology of Reproduction in the Squirrel Monkey (Saimiri sciureus): I. The Estrus Cycle.” Primates 11:125—34.

*Talmage-Riggs, G., and S. Anschel (1973) “Homosexual Behavior and Dominance in a Group of Captive Squirrel Monkeys (Saimiri sciureus).” Folia Primatologica 19:61—72.

*Travis, J. C., and W. N. Holmes (1974) “Some Physiological and Behavioral Changes Associated with Oestrus and Pregnancy in the Squirrel Monkey (Saimiri sciureus).” Journal of Zoology, London 174:41— 66.

*Vasey, P. L.(1995) “Homosexual Behavior in Primates: A Review of Evidence and Theory.” International Journal of Primatology 16:173—204.

Verreaux’s Sifakas live in cosexual groups of up to 12 individuals and sometimes associate as male-female pairs. As in most Lemurs, females are generally dominant to males in this species. Females typically remain in their birth group for life, while males leave their group on maturing and transfer between groups several times throughout their lives. The mating system has elements of POLYGYNANDRY, that is, females generally mate with more than one male and vice versa. Lesser Bushbabies generally live in family groups consisting of females and their offspring along with peripheral males. They are often found singly or in pairs and may form sleeping groups of up to seven individuals.

Behavioral Expression: Male Verreaux’s Sifakas sometimes mount other males during the mating season. The mounted animal—usually a younger adult or adolescent male—often snaps at the mounter and tries to wriggle free (as do females trying to escape from unwelcome heterosexual advances). In Lesser Bushbabies, females occasionally mount and thrust against each other when in heat. Like other species of Bushbabies, the genitals of female Lesser Bushbabies are unusual in several respects. The clitoris is long and pendulous, greatly resembling the male’s penis, and the urethra extends through to the tip of the organ, so that females urinate through the clitoris rather than through a urethral opening near the vagina. Females do not menstruate, and in fact the vagina remains closed at all times except during the mating season (which lasts no more than two to three weeks and occurs twice a year).

Frequency: Homosexual mounting probably occurs only occasionally in Verreaux’s Sifakas and Lesser Bushbabies. However, one study of wild Verreaux’s Sifakas found that 3 out of 21 mountings (14 percent) were between males.

Orientation: Lemurs and Bushbabies that participate in same-sex mounting probably also engage in heterosexual activity, although too little is known about individual life histories in these species to draw any firm conclusions.

Many heterosexual copulations in Verreaux’s Sifakas—more than two-thirds in some populations—do not involve penetration or ejaculation, often because the female resists the mating attempt and wriggles free. Females sometimes also mate when they are not in heat: for some individuals, 30–80 percent of their sexual activity is nonprocreative, taking place during times when they cannot conceive. In some populations females also delay reproducing for several years, and only slightly more than half of all adult females reproduce each year. Infanticide occurs occasionally in this species, and possibly also abortions. In Lesser Bushbabies, heterosexual copulations can be lengthy—more than nine minutes in some cases—and a female often bites the male, “boxes” him with her hands, and tries to push him off or get away from him during mating.

*asterisked references discuss homosexuality/transgender

*Andersson, A. B. (1969) “Communication in the Lesser Bushbaby (Galago senegalensis moholi).” Master’s thesis, Witwatersrand University.

Bearder, S. K., and G. A. Doyle (1974) “Field and Laboratory Studies of Social Organization in Bushbabies (Galago senegalensis).” Journal of Human Evolution 3:37-50.

Brockman, D. K., and P. L. Whitten (1996) “Reproduction in Free-Ranging Propithecus verreauxi: Estrus and the Relationship Between Multiple Partner Matings and Fertilization.” American Journal of Physical Anthropology 100:57–69.

Butler, H. (1967) “The Oestrus Cycle of the Senegal Bush Baby (Galago senegalensis senegalensis) in the Sudan.” Journal of Zoology, London 151:143–62.

Dixson, A. F. (1995) “Sexual Selection and the Evolution of Copulatory Behavior in Nocturnal Prosimians.” In L. Alterman, G. A. Doyle, and M. K. Izard, eds., Creatures of the Dark: The Nocturnal Prosimians, pp. 93–118. New York: Plenum Press.

*Doyle, G. A. (1974a) “Behavior of Prosimians.” Behavior of Nonhuman Primates 5:154–353.

———(1974b) “The Behavior of the Lesser Bushbaby.” In R. D. Martin, G. A. Doyle, and A. C. Walker, eds., Prosimian Biology, pp. 213–31. Pittsburgh: University of Pittsburgh Press.

Doyle, G. A., A. Pelletier, and T. Bekker (1967) “Courtship, Mating, and Parturition in the Lesser Bushbaby (Galago senegalensis moholi) Under Semi-Natural Conditions.” Folia Primatologica 7:169-97.

Kubzdela, K. S., A. F. Richard, and M. E. Pereira (1992) “Social Relations in Semi-Free-Ranging Sifakas (Propithecus verreauxi verreauxi) and the Question of Female Dominance.” American Journal of Primatology 28:139–45.

Lipschitz, D. L. (1996) “Male Copulatory Patterns in the Lesser Bushbaby (Galago moholi) in Captivity.” International Journal of Primatology 17:987–1000.

Lowther, F. D. L. (1940) “A Study of the Activities of a Pair of Galago senegalensis moholi in Captivity, Including the Birth and Postnatal Development of Twins.” Zoologica 25:433-65.

Richard, A., (1992) “Aggressive Competition Between Males, Female-Controlled Polygyny, and Sexual Monomorphism in a Malagasy Primate, Propithecus verreauxi.” Journal of Human Evolution 22:395–406.

———(1978) Behavioral Variation: Case Study of a Malagasy Lemur. Lewisburg, Pa.: Bucknell University Press.

*————(1974a) “Intra-specific Variation in the Social Organization and Ecology of Propithecus verreauxi.” Folia Primatologica 22:178–207.

*———(1974b) “Patterns of Mating in Propithecus verreauxi verreauxi.” In R. D. Martin, G. A. Doyle, and A. C. Walker, eds., Prosimian Biology, pp. 49–74. London: Duckworth; Pittsburgh: University of Pittsburgh Press.

Richard, A., P. Rakotomanga, and M. Schwartz (1991) “Demography of Propithecus verreauxi at Beza Ma-hafaly, Madagascar: Sex Ratio, Survival, and Fertility, 1984–1988.” American Journal of Physical Anthropology 84:307–22.

DOLPHINS AND WHALES

Although little is known about their social organization, it appears that Botos are largely solitary animals that occasionally associate in groupings of up to a dozen or more individuals. Larger aggregations generally occur at feeding areas, and Botos may even coordinate their fishing attempts with other species, such as the giant river otter (Pteronura brasiliensis). The Boto mating system is probably polygamous.

Behavioral Expression: Male Botos participate in a wide variety of homosexual interactions, including mating with each other using fully three different types of penetration: one male may insert his erect penis into the genital slit of the other, into his anus, or into his blowhole. When engaging in anal or genital-slit intercourse, one male swims upside down beneath the other one as in heterosexual copulation; blowhole mating occurs with the inserting male above the other one. If there is an age difference between the males, typically the older one penetrates the younger one. Males also rub their genital openings or erect penises against each other; alternatively, one male might rub his head against the other’s genitals, stimulating an erection. Pairs of males who interact sexually also display a great deal of affection toward one another, caressing each other with their beak or flippers, brushing against one another, swimming side by side while touching each other’s body, flippers, or flukes, surfacing to breathe simultaneously, or playing and resting together. Male homosexual encounters can be quite lengthy—continuing for a whole afternoon, for example—although if mating occurs, the actual penetration lasts for only about one minute (in anal intercourse).

Male Botos also engage in homosexual activity with another species of Amazon River dolphin, the Tucuxi (Sotalia fluviatilis). In these interspecies encounters, genital slit intercourse between males involves the same belly-to-belly position described above, but sometimes the penetrating animal twists around so that his head faces in the opposite direction (while still remaining inserted in the other male). In addition to caresses and genital rubbing, homosexual activity sometimes includes more unusual behavior: a male Boto was once seen gently taking a Tucuxi’s entire head into his mouth, in an apparently affectionate gesture.

Frequency Homosexual activity is common in captive Botos; its prevalence among wild animals is not known. Similarly, sexual behavior between Botos and Tucuxis has only been seen in captivity, but these two species do occasionally interact with one another in the wild.

Orientation: Because homosexual behavior has been studied in detail only in captive male Botos without access to females, it is not known whether this behavior occurs in other contexts, or if it is simply an expression of a latent or “situational” bisexual potential. However, given the varied and generally plastic nature of dolphin sexuality, it is likely that homosexual or bisexual expression is a basic component of Boto social life for at least some individuals.

Male and female Botos sometimes engage in nonreproductive matings: heterosexual blowhole copulations have been observed, and a male will also sometimes rub his penis against the female’s fins or flukes, especially if she does not permit him to copulate vaginally. In addition, heterosexual matings can be remarkably frequent and prolonged affairs: one male and female were seen to mate once every four minutes for a virtually continuous period of over three hours. However, females are not always willing participants in such repeated copulations, often fleeing into shallow waters to avoid males that are harassing them. Females that cannot escape may be attacked and bitten around the genital area by males. Masturbation is also common in Botos: males rub the penis with one of their fins, females sometimes try to insert objects into the genital slit, while both sexes rub their genitals against underwater objects or surfaces. Botos have also developed an alternate parenting or “baby-sitting” arrangement of communal nursery groups. Young Botos gather together in shallow water, forming what are sometimes known as CRÈCHES that contain both calves and older juveniles; these groups offer them safety in numbers while their parents feed on their own.

*asterisked references discuss homosexuality/transgender

*Best, R. C., and V. M. F. da Silva (1989) “Amazon River Dolphin, Boto, Inia geoffrensis (de Blainville, 1817).” In S. H. Ridgway and R. Harrison, eds., Handbook of Marine Mammals, vol. 4: River Dolphins and the Larger Toothed Whales, pp. 1–23. London: Academic Press.

*Caldwell, M. C., D. K. Caldwell, and R. L. Brill (1989) “Inia geoffrensis in Captivity in the United States.” In W. F. Perrin, R. L. Brownell, Jr., Z. Kaiya, and L. Jiankang, eds., Biology and Conservation of the River Dolphins, pp. 35–41. Occasional Papers of the IUCN Species Survival Commission no. 3. Gland, Switzerland: International Union for Conservation of Nature and Natural Resources.

*Caldwell, M. C., D. K. Caldwell, and W. E. Evans (1966) “Sounds and Behavior of Captive Amazon Freshwater Dolphins, Inia geoffrensis.” Los Angeles County Museum Contributions in Science 108:1–24.

Layne, J. N. (1958) “Observations on Freshwater Dolphins in the Upper Amazon.” Journal of Mammology 39:1–22.

*Layne, J. N, and D. K. Caldwell (1964) “Behavior of the Amazon Dolphin, Inia geoffrensis (Blainville), in Captivity.” Zoologica 49:81–108.

*Pilleri, G., M. Gihr, and C. Kraus (1980) “Play Behavior in the Indus and Orinoco Dolphin (Platanista indi and Inia geoffrensis).” Investigations on Cetacea 11:57–107.

*Renjun, L., W. Gewalt, B. Neurohr, and A. Winkler (1994) “Comparative Studies on the Behavior of Inia geoffrensis and Lipotes vexillifer in Artificial Environments.” Aquatic Mammals 20:39–45.

*Spotte, S. H. (1967) “Intergeneric Behavior Between Captive Amazon River Dolphins Inia and Sotalia.” Underwater Naturalist 4:9-13.

*Sylvestre, J.-P. (1985) “Some Observations on Behavior of Two Orinoco Dolphins (Inia geoffrensis humboldtiana [Pilleri and Gihr 1977]), in Captivity, at Duisburg Zoo.” Aquatic Mammals 11:58–65.

Trujillo, F. (1996) “Seeing Fins.” BBC Wildlife 14:22–28.

Bottlenose Dolphins have a highly developed social system characterized by four basic social units: mother-calf pairs, groups of adolescents (often male-only, or with a preponderance of males), bands of up to a dozen adult females and their young, and adult males in pair-bonds (and less commonly, on their own). Spinner Dolphins may have a more fluid social organization, although coalitions of males can sometimes be recognized, as well as schools of a thousand or more individuals. The heterosexual mating system is poorly understood; however, there are no strong male-female bonds, and animals probably mate with multiple partners.

Behavioral Expression: In both Bottlenose and Spinner Dolphins, animals of the same sex frequently engage in affectionate and sexual activities with each other that have many of the elements of heterosexual courtship and sexuality. For example, two males or two females often rub their bodies together, mouthing and nuzzling one another, and may caress and stroke each other—simultaneously or alternately—with their fins, flukes, snouts (or “beaks”), and heads. Sometimes this is accompanied by playful rolling, chasing, pushing, and leaping. During this activity—which can last anywhere from several minutes to several hours—males may display erect penises. More overt homosexual activity takes a variety of forms. One animal might stroke or gently probe the other’s genital area with the soft tips of its flukes or flippers. Female Spinner Dolphins sometimes even “ride” on each other’s dorsal fin—one inserts her fin into the other’s vulva or genital slit, then the two swim together in this position. Among Bottlenose females, direct stimulation of the clitoris is a prominent feature of homosexual interactions. Two females often take turns rubbing each other’s clitoris, using either the snout, flippers, or flukes, or else actively masturbate against their partner’s appendages. Females may also clasp one another in a belly-to-belly position (as in heterosexual mating) and thrust against each other.

Homosexual interactions also involve a form of “oral” sex in which one animal rubs and nuzzles the other’s genitals with its snout or beak; because both males and females have a genital slit or opening, penetration is also possible in this fashion for both sexes. One animal might insert the tip of its beak into the other’s genitals or perhaps just use its lower jaw to penetrate and stimulate his or her partner. Sometimes this develops into a sexual activity known as BEAK-GENITAL PROPULSION, in which one partner inserts its beak into the other’s genitals and gently propels the two of them forward, maintaining penetration while they swim together. The lower animal may also turn on its side or rotate belly up during this activity. Male Dolphins sometimes rub their erect penises on one another’s body or genital area. This may lead to copulation, in which one male swims upside down underneath the other, pressing his genitals against the other and even inserting his penis into the genital slit (or less commonly, anus) of the male above him (this same position is used in heterosexual intercourse). The two partners may switch positions, alternating during the same session, or perhaps exchanging “roles” over a longer period. If there is an age difference between male partners, either may penetrate the other, and Bottlenose adolescents have even been observed penetrating much older males. Groups of three or four males may engage in homosexual activity together, or one male may masturbate (by rubbing his penis on rocks or sand) while other males are coupling nearby. Homosexual activity is sometimes accompanied by aggressive behaviors, but these can also occur during heterosexual interactions (males and females have been observed diving forcefully at each other, for example, and violently ramming their foreheads together as a prelude to mating). In Spinner Dolphins, groups of a dozen or more dolphins of both sexes sometimes gather together in near “orgies” of caressing and sexual behavior (both same-sex and opposite-sex); these groups are known as WUZZLES.

Male Bottlenose Dolphins often form life-long pair-bonds with each other. Adolescent and younger males typically live in all-male groups in which homosexual activity is common; within these groups, a male begins to develop a strong bond with a particular partner (usually of the same age) with whom he will spend the rest of his life. The two Dolphins become constant companions, often traveling widely; although sexual activity probably declines as they get older, it may continue to be a regular feature of such partnerships. Paired males sometimes take turns guarding or remaining vigilant while their partner rests. They also defend their mates against predators such as sharks and protect them while they are healing from wounds inflicted during predators’ attacks. Sometimes three males form a tightly bonded trio. On the death of his partner, a male may spend a long time searching for a new male companion—usually unsuccessfully, since most other males in the community are already paired and will not break their bonds. If, however, he can find another “widower” whose male partner has died, the two may become a couple.

Male Bottlenose Dolphins also sometimes aggressively pursue and copulate with male Atlantic Spotted Dolphins (Stenella frontalis), both adults and juveniles. After an initial chase, the Bottlenose male typically arches and rubs his body and erect penis against the Spotted male, then mounts (and often penetrates) him from an upright, sideways position. This mounting position is distinct from the upside-down, belly-to-belly approach generally used for within-species sexual encounters. Sometimes a pair of Bottlenose males pursue a Spotted male and both partners mount him at the same time. Though often playful, this high-energy interspecies homosexual activity may also be accompanied by aggressive behaviors such as tail slaps, threatening postures, and squawking vocalizations (also part of heterosexual interactions between these two species and among Bottlenose Dolphins, as noted above). In fact, groups of Spotted Dolphins—sometimes accompanied by Bottlenose males—may band together to chase off Bottlenose males that are engaging in these more aggressive sexual interactions. However, even when this activity is accompanied by overt aggression, Bottlenose and Spotted males that interact sexually with one another may later also band together and cooperate with one another. Male Atlantic Spotted Dolphins also engage in homosexual activity with each other, and adults sometimes even copulate with male calves of their own species. In one such instance, adult-juvenile homosexual activity was preceded by a vocalization known as a GENITAL BUZZ, in which the adult male directed a stream of low-pitched, rapid buzzing clicks toward the genital area of the male calf. This sound, which is also a component of heterosexual courtship in this species, may serve as a form of acoustic “foreplay,” actually stimulating the genitals of the recipient via the strongly pulsed sound waves. Bottlenose and Spinner Dolphins of both sexes have also been observed participating in homosexual activity with other species of dolphins in captivity, such as Pacific Striped Dolphins (Lagenorhynchus obliquidens), Common Dolphins (Delphinus delphis), Bridled Dolphins (Stenella attenuata), and False Killer Whales (Pseudorca crassidens).

Frequency: Homosexual interactions are a frequent and regular occurrence in wild Dolphins, particularly among groups of younger Bottlenose males. In mixed-sex groups in captivity, homosexual behavior occurs with equal frequency—and in some cases, more often—than heterosexual activity. Male couples are a ubiquitous feature of many Bottlenose communities; in some cases, more than three-quarters of all males live in same-sex pair-bonds. About 30 percent of interactions between wild Bottlenose and Atlantic Spotted Dolphins include homosexual activities (often accompanied by aggressive behaviors).

Orientation: The lives of male Bottlenose Dolphins are characterized by extensive bisexuality, combined with periods of exclusive homosexuality. As adolescents and young males, they have regular homosexual interactions in all-male groups, sometimes alternating with heterosexual activity. From age 10 onward, most male Dolphins form pair-bonds with another male, and because they do not usually father calves until they are 20–25 years old, this can be an extended period—10–15 years—of principally same-sex interaction. Later, when they begin mating heterosexually, they still retain their primary male pair-bonds, and in some populations male pairs and trios cooperate in herding females or in interacting homosexually with Spotted Dolphins. Because only five or six calves are born to a community each year, however, probably no more than half of the adult males are heterosexually active each mating season (and perhaps far fewer if, as some biologists have suggested, only two or three males monopolize all copulations). Males that do not form same-sex pairs may have a more exclusively heterosexual orientation. Female Bottlenose Dolphins probably have a similar pattern of bisexual interactions overlaid on a largely female-centered social framework. Spinner Dolphins seem to be more uniformly bisexual without extensive periods of exclusive homosexuality, often alternating between same-sex and opposite-sex interactions in quick succession (this sort of concurrent bisexuality has also been observed in Bottlenose and Atlantic Spotted Dolphins). In captivity, though, Spinners exhibit a continuum, with homosexual activity making up only 10 percent of some individuals’ behavior, half to two-thirds for other animals, while some Dolphins interact almost exclusively with animals of the same sex.

Nonprocreative activities are a hallmark of Dolphin heterosexual interactions. Virtually all of the nonreproductive behaviors described above for same-sex interactions also occur between males and females, including beak-genital propulsion and stimulation of the genitals with the flippers, flukes, and snout. Group sexual activity—much of it heterosexual but nonreproductive—occurs in Spinner wuzzles, and courtship and sexual activity in Bottlenose Dolphins sometimes involves up to ten animals at a time. Female sexuality in Dolphins is often pleasure-oriented, focusing on stimulation of the clitoris as much if not more so than vaginal penetration and insemination. Bottlenose Dolphins mate and interact sexually at all times of the year, not just during the mating season; in Spinner Dolphins (and other species as well), males have a yearly sexual cycle, with significant periods when they are probably unable to fertilize females. In addition, masturbation is a prominent feature of Bottlenose sexual life: both males and females rub their genitals against inanimate objects or other animals, sometimes even developing the activity into a playful “game.” Females have even been observed using the muscles of their vaginal region to carry small rubber balls, which they then rub their genitals against. Young Dolphins are sexually precocious, and incestuous copulations have been observed between males a few months old and their mothers. Both male and female Bottlenose Dolphins also interact heterosexually with Atlantic Spotted Dolphins, often using the same sideways mounting position and aggressive behaviors described above for interspecies homosexual encounters. Adults often direct sexual behaviors toward juveniles during these interactions, and female Bottlenose Dolphins have even been seen sideways mounting younger male Spotteds (REVERSE mounting). Many heterosexual interactions in captivity also take place between Dolphins of different species.

Interestingly, this broad variety of heterosexual expression takes place in a larger social framework of primarily separate spheres of activity for males and females, at least in Bottlenose Dolphins. As described above, the two sexes are largely segregated for most of their lives, often socializing in same-sex groups. Furthermore, many animals spend a large portion of their lives uninvolved in breeding: most males do not begin mating until they are at least 20 years old (well beyond the time they become sexually mature), and many Dolphins of that age still do not participate in heterosexual mating. Females breed only once every three to six years, and nearly a quarter of the adult female population may not be involved in reproductive activities at any time. When females do bear calves, they are often assisted by another adult—usually a female—who acts as a “baby-sitter,” taking care of the calf while she feeds. Males do not generally parent, and indeed, most Bottlenose calves are sired by males from outside the community. In Spinner Dolphins, “helpers” may be of both sexes, and parental helping behavior has also been observed between Dolphins of different species, for example, by adult Common, Spotted, and Spinner Dolphins toward Bottlenose calves. At times, however, this behavior (within the same species) may be less than “helpful,” especially when it involves males. In captivity, “baby-sitting” males have been observed harassing mothers, trying to “kidnap” their calves, and even behaving sexually toward the infants (including trying to mate with them). Pairs and trios of males in some Bottlenose populations also occasionally harass adult females, chasing, herding, and even “kidnapping” and attacking them (e.g., with charges, bites, tail slaps, and body slams) in an attempt to mate with them. Recently, infanticide has also been discovered in some wild Bottlenose communities.

Homosexual activity has also been reported in (captive) male Harbor Porpoises (Phocoena phoecena) and Commerson’s Dolphins (Cephalorhynchus commersoni), among others. Intersexual or hermaphrodite individuals (possessing external female genitals along with testes and other internal male reproductive organs) occasionally occur in Striped Dolphins (Stenella coeruleoalba).

*asterisked references discuss homosexuality/transgender

*Amudin, M. (1974) “Some Evidence for a Displacement Behavior in the Harbor Porpoise, Phocoena phocoena (L.). A Causal Analysis of a Sudden Underwater Expiration Through the Blow Hole.” Revue du comportement animal 8:39–45.

*Bateson, G. (1974) “Observations of a Cetacean Community.” In J. McIntyre, ed., Mind in the Waters, pp. 146–65. New York: Charles Scribner’s Sons.

*Brown, D. H., D. K. Caldwell, and M. C. Caldwell (1966) “Observations on the Behavior of Wild and Captive False Killer Whales, With Notes on Associated Behavior of Other Genera of Captive Delphinids.” Contributions in Science (Los Angeles County Museum of Natural History) 95:1–32.

*Brown, D. H., and K. S. Norris (1956) “Observations of Captive and Wild Cetaceans.” Journal of Mammalogy 37:311–26.

*Caldwell, M. C., and D. K. Caldwell (1977) “Cetaceans.” In T.A. Sebeok, ed., How Animals Communicate, pp. 794–808. Bloomington: Indiana University Press.

*———(1972) “Behavior of Marine Mammals.” In S. H. Ridgway, ed., Mammals of the Sea: Biology and Medicine, pp. 419-65. Springfield: Charles C. Thomas.

*———(1967) “Dolphin Community Life.” Quarterly of the Los Angeles County Museum of Natural History 5(4):12–15.

*Connor, R. C., and R. A. Smolker (1995) “Seasonal Changes in the Stability of Male-Male Bonds in Indian Ocean Bottlenose Dolphins (Tursiops sp.).” Aquatic Mammals 21:213–16.

*Connor, R. C., R. A. Smolker, and A. F. Richards (1992) “Dolphin Alliances and Coalitions.” In A. H. Harcourt and F. B. M. de Waal, eds., Coalitions and Alliances in Humans and Other Animals, pp. 415–43. Oxford: Oxford University Press.

*Dudok van Heel, W. H., and M. Mettivier (1974) “Birth in Dolphins (Tursiops truncatus) in the Dolfinar-ium, Harderwijk, Netherlands.” Aquatic Mammals 2:11–22.

*Félix, F. (1997) “Organization and Social Structure of the Coastal Bottlenose Dolphin Tursiops truncatus in the Gulf of Guayaquil, Ecuador.” Aquatic Mammals 23:1-16.

*Herzing, D. L. (1996) “Vocalizations and Associated Underwater Behavior of Free-ranging Atlantic Spotted Dolphins, Stenella frontalis and Bottlenose Dolphins, Tursiops truncatus.” Aquatic Mammals 22:61–79.

*Herzing, D. L., and C. M. Johnson (1997) “Interspecific Interactions Between Atlantic Spotted Dolphins (Stenella frontalis) and Bottlenose Dolphins (Tursiops truncatus) in the Bahamas, 1985–1995.” Aquatic Mammals 23:85–99.

*Irvine, A. B., M. D. Scott, R. S. Wells, and J. H. Kaufmann (1981) “Movements and Activities of the Atlantic Bottlenose Dolphin, Tursiops truncatus, Near Sarasota, Florida.” Fishery Bulletin, U.S. 79:671–88.

*McBride, A. F., and D. O. Hebb (1948) “Behavior of the Captive Bottle-Nose Dolphin, Tursiops truncatus.” Journal of Comparative and Physiological Psychology 41:111–23.

*Nakahara, F., and A. Takemura (1997) “A Survey on the Behavior of Captive Odontocetes in Japan.” Aquatic Mammals 23:135–43.

*Nishiwaki, M. (1953) “Hermaphroditism in a Dolphin (Prodelphinus caeruleo-albus).” Scientific Reports of the Whales Research Institute 8:215–18.

*Norris, K. S., and T. P. Dohl (1980a) “Behavior of the Hawaiian Spinner Dolphin, Stenella longirostris.” Fishery Bulletin, U.S. 77:821-49.

*———(1980b) “The Structure and Functions of Cetacean Schools.” In L. M. Herman, ed., Cetacean Behavior: Mechanisms and Functions, pp. 211–61. New York: Wiley-InterScience.

*Norris, K. S., B. Würsig, R. S. Wells, and M. Würsig (1994) The Hawaiian Spinner Dolphin. Berkeley: University of California Press.

*Östman, J. (1991) “Changes in Aggressive and Sexual Behavior Between Two Male Bottlenose Dolphins (Tursiops truncatus) in a Captive Colony.” In K. Pryor and K. S. Norris, eds., Dolphin Societies: Discoveries and Puzzles, pp. 304-17. Berkeley: University of California Press.

Patterson, I. A. P., R. J. Reid, B. Wilson, K. Grellier, H. M. Ross, and P. M. Thompson (1998) “Evidence for Infanticide in Bottlenose Dolphins: an Explanation for Violent Interactions with Harbor Porpoises?” Proceedings of the Royal Society of London, Series B 265:1167–70.

*Saayman, G. S., and C. K. Tayler (1973) “Some Behavior Patterns of the Southern Right Whale, Eubalaena australis.” Zeitschrift für Säugetierkunde 38:172–83.

Samuels, A., and T. Gifford (1997) “A Quantitative Assessment of Dominance Among Bottlenose Dolphins.” Marine Mammal Science 13:70–99.

Shane, S. H. (1990) “Behavior and Ecology of the Bottlenose Dolphin at Sanibel Island, Florida.” In S. Leatherwood and R. R. Reeves, eds., The Bottlenose Dolphin, pp. 245-65. San Diego: Academic Press.

Shane, S. H., R. S. Wells, and B. Würsig (1986) “Ecology, Behavior, and Social Organization of the Bottlenose Dolphin: A Review.” Marine Mammal Science 2:34–63.

*Tavolga, M. C. (1966) “Behavior of the Bottlenose Dolphin (Tursiops truncatus): Social Interactions in a Captive Colony.” In K. S. Norris, ed., Whales, Dolphins, and Porpoises, pp. 718-30. Berkeley: University of California Press.

*Tayler, C. K., and G. S. Saayman (1973) “Imitative Behavior by Indian Ocean Bottlenose Dolphins (Tursiops aduncus) in Captivity.” Behavior 44:286-98.

*Wells, R. S. (1995) “Community Structure of Bottlenose Dolphins Near Sarasota, Florida.” Paper presented at the 24^th International Ethological Conference, Honolulu, Hawaii.

*———(1991) “The Role of Long-Term Study in Understanding the Social Structure of a Bottlenose Dolphin Community.” In K. Pryor and K. S. Norris, eds., Dolphin Societies: Discoveries and Puzzles, pp. 199–225. Berkeley: University of California Press.

*———(1984) “Reproductive Behavior and Hormonal Correlates in Hawaiian Spinner Dolphins, Stenella longirostris.” In W. E Perrin, R. L. Brownell, Jr., and D. P. DeMaster, eds., Reproduction in Whales, Dolphins, and Porpoises, pp. 465–72. Report of the International Whaling Commission, Special Issue 6. Cambridge, UK: International Whaling Commission.

*Wells, R. S., K. Bassos-Hull, and K. S. Norris (1998) “Experimental Return to the Wild of Two Bottlenose Dolphins.” Marine Mammal Science 14:51–71.

*Wells, R. S., M. D. Scott, and A. B. Irvine (1987) “The Social Structure of Free-ranging Bottlenose Dolphins.” In H. Genoways, ed., Current Mammalogy, vol. 1, pp. 247–305. New York: Plenum Press.

Killer Whales live in a complex society based on a female-centered social unit called the MATRILINEAL GROUP. This is made up of an adult female, the matriarch—usually reproductively active, but sometimes older and postreproductive—her young, and any adult sons of hers. Sometimes her mother or grandmother is also present, and possibly her brothers or uncles. Matrilineal groups usually contain three or four Orcas (although some have up to nine); these groups are organized into larger social units known as PODS, which tend to socialize together and share a common dialect in their vocalizations. Some populations of Killer Whales are TRANSIENTS, who travel widely in smaller groups (occasionally singly) and are less vocal. Unlike nontransient or RESIDENT Orcas, they feed primarily on marine mammals rather than fish.

Behavioral Expression: Homosexual interactions are an integral and important part of male Orca social life. During the summer and fall—when resident pods join together to feast on the salmon runs—males of all ages often spend the afternoons in sessions of courtship, affectionate, and sexual behaviors with each other. A typical homosexual interaction begins when a male Killer Whale leaves his matrilineal group to join a temporary male-only group; a session can last anywhere from a few minutes to more than two hours, with the average length being just over an hour. Usually only two Orcas participate at a time, although groups of three or four males are not uncommon, and even five participants at one time have been observed. The males roll around with each other at the surface, splashing and making frequent body contact as they rub, chase, and gently nudge one another. This is usually accompanied by acrobatic displays such as vigorous slapping of the water with the tail or flippers, lifting the head out of the water (SPYHOPPING), arching the body while floating at the surface or just before a dive, and vocalizing in the air. Particular attention is paid by the males to each other’s belly and genital region, and often they initiate a behavior known as BEAK-GENITAL ORIENTATION, which is also seen in heterosexual courtship and mating sequences. Just below the surface of the water, one male swims underneath the other in an upside-down position, touching and nuzzling the other’s genital area with his snout or “beak.” The two males swim together in this position, maintaining beak-genital contact as the upper one surfaces to breathe; then they dive together, spiraling down into the depths in an elegant double-helix formation. As a variation on this sequence, sometimes one male will arch his tail flukes out of the water just before a dive, allowing the other male to rub his beak against his belly and genital area. When the pair resurfaces after three to five minutes, they repeat the sequence, but with the positions of the two males reversed. In fact, almost 90 percent of all homosexual behaviors are reciprocal, in that the males take turns touching or interacting with one another. During all of these interactions, the Orcas frequently display their erect penises, rolling at the surface or underwater to reveal the distinctive yard-long, pink organs. One male may even attempt to insert his penis—which has a prehensile tip that can be independently moved—into the genital slit of another male (although this has yet to be fully verified).

Although males of all ages participate in homosexual activities, this behavior is most prevalent among “adolescent” Orcas (sexually mature individuals 12–25 years old). More than three-quarters of all sessions involve males who are more than five years apart in age, although age-mates also interact together (especially among adolescents). Occasionally, adult-only homosexual activity (i.e., between males 25 years and older) takes place. Some males have favorite partners with whom they interact year after year, and they may even develop a long-lasting “friendship” or pairing with one particular male. Other males seem to interact with a wide variety of different partners. Most participants in homosexual activity come from different matrilineal groups and are therefore not related; however, more than a third of the sessions include brothers or half brothers (along with other participants), while 9 percent are entirely incestuous.

Frequency: Homosexual interactions are common in Orcas during the summer and fall, especially during August and September—anywhere from 6 to 30 or more sessions of same-sex activity may occur each season in some populations. On average, each male participates in one or two sessions each season, spending about 10 percent of his time in this activity; however, some males may be involved in as many as seven or eight sessions and devote more than 18 percent of their time to this behavior. Overall, in some populations more than three-quarters of observed sexual activity occurs between males.

Orientation: Anywhere from one-third to more than one-half of all males engage in homosexual interactions. This behavior is especially prevalent among younger Orcas: adolescent males participate four times more often than adults. Many males that engage in this behavior are probably bisexual, since they also court and mate with females. However, there are clear differences between individual males in their affinity or “preference” for homosexual interactions: some Killer Whales participate often and actively seek out male partners, while others are much less involved.

Orca communities contain a sizable population of older, nonbreeding females. With an average life span of 50 years—and a possible maximum longevity of 80 years—female Killer Whales can experience a postreproductive period of up to 30 years. In some populations, one-third to one-half of adult females are postreproductive, and it is estimated that a stable population can support as many as two-thirds postreproductive females. Many such females are the matriarchs of their group, and their leadership continues even if it means the ultimate demise of the pod: if there are only male offspring, a pod will eventually disappear upon the death of its matriarch, since there are no breeding females to continue the matriline. Many postreproductive females, while not breeding themselves, act as “baby-sitters” or helpers in an elaborate communal parenting system. They, along with breeding females, nonbreeding adult and adolescent females, and adult males, frequently take care of calves when their mothers are away or attending to a sibling. Since most breeding females reproduce only once every five years, there is a large pool of potential helpers who are not themselves parents in the population. It is estimated that each calf may be baby-sat as often as once a day during particularly busy times. Although postreproductive females no longer procreate, they may still participate in sexual activity, often with younger males. Several other types of nonprocreative heterosexuality also occur among Orcas: pregnant females have been observed engaging in courtship and sexual behavior with males, while heterosexual interactions also occur between adults or adolescents (of both sexes) and youngsters (juveniles as well as calves). Some incestuous sexual activity has also been documented, for example between an adolescent male and his juvenile sister. Finally, heterosexual interactions do not always involve just two individuals—sometimes a trio of two males and a female will engage in courtship activity together, and one male may even touch and hold the female while the other copulates with her.

Same-sex activity occurs in several other species of toothed whales. Pairs of male Sperm Whales (Physeter macrocephalus) that may be homosexually bonded occur in some populations. In the waters surrounding New Zealand, for example, 3–5 percent of males are found in such pairs, probably belonging to a semiresident population. These male couples travel together closely and are usually composed of two adults or one older and one younger male. Sexual interactions leading to orgasm also take place in groups of (primarily younger) male Sperm Whales off the coast of Dominica. Homosexual activity has been seen in captive male Beluga Whales (Delphinapterus leucas) as well. In addition, hermaphrodite individuals occasionally occur in Belugas and possibly also in Sperm Whales. One Beluga, for example, had male external genitalia combined with a complete set of both male and female internal reproductive organs (i.e., two ovaries and two testes).

*asterisked references discuss homosexualityltransgender

*Ash, C. E. (1960) “Hermafrodite spermhval/Hermaphrodite Sperm Whale.” Norsk Hvalfangst-Tidende 49:433.

*Balcomb, K. C. III, J. R. Boran, R. W. Osborne, and N. J. Haenel (1979) “Observations of Killer Whales (Orcinus orca) in Greater Puget Sound, State of Washington.” Unpublished report, Moclips Cetologi-cal Society, Friday Harbor, Wash.; 46 pp. (available at National Marine Mammal Laboratory Library, Seattle, Wash.).

*De Guise, S., A. Lagacé, and P. Béland (1994) “True Hermaphroditism in a St. Lawrence Beluga Whale (Delphinapterus leucas).” Journal of Wildlife Diseases 30:287–90.

Ford, J. K. B., G. M. Ellis, and K. C. Balcomb (1994) Killer Whales: The Natural History and Genealogy of Orcinus orca in British Columbia and Washington State. Vancouver: UBC Press; Seattle: University of Washington Press.

*Gaskin, D. E. (1982) The Ecology of Whales and Dolphins. London: Heinemann.

*———(1971) “Distribution and Movements of Sperm Whales (Physeter catodon L.) in the Cook Strait Region of New Zealand.” Norwegian Journal of Zoology 19:241-59.

*———(1970) “Composition of Schools of Sperm Whales Physeter catodon Linn. East of New Zealand.” New Zealand Journal of Marine and Freshwater Research 4:456–71.

*Gewalt, W. (1976) Der Weisswal, Delphinapterus leucas [The Beluga]. Wittenberg: A. Ziemsen-Verlag

*Gordon, J., and R. Rosenthal (1996) “Sperm Whales: The Real Moby Dick.” BBC-TV productions, UK.

*Haenel, N. J. (1986) “General Notes on the Behavioral Ontogeny of Puget Sound Killer Whales and the Occurrence of Allomaternal Behavior.” In B. C. Kirkevold and J. S. Lockard, eds., Behavioral Biology of Killer Whales, pp. 285–300. New York: Alan R. Liss.

*Jacobsen, J. K. (1990) “Associations and Social Behaviors Among Killer Whales (Orcinus orca) in the Johnstone Strait, British Columbia, 1979–1986.” Master’s thesis, Humboldt State University.

*———(1986) “The Behavior of Orcinus orca in the Johnstone Strait, British Columbia.” In B.C. Kirkevold and J. S. Lockard, eds., Behavioral Biology of Killer Whales, pp. 135–85. New York: Alan R. Liss.

Martinez, D. R., and E. Klinghammer (1978) “A Partial Ethogram of the Killer Whale (Orcinus orca L.).” Carnivore 1:13–27.

Olesiuk, P. F., M. A. Bigg, and G. M. Ellis (1990) “Life History and Population Dynamics of Resident Killer Whales (Orcinus orca) in the Coastal Waters of British Columbia and Washington State.” In P. S. Hammond, S. A. Mizroch, and G. P. Donovan, eds., Individual Recognition of Cetaceans: Use of Photo-Identification and Other Techniques to Estimate Population Parameters, pp. 209-43. Report of the International Whaling Commission, Special Issue 12. Cambridge, UK: International Whaling Commission.

*Osborne, R. W. (1986) “A Behavioral Budget of Puget Sound Killer Whales.” In B. C. Kirkevold and J. S. Lockard, eds., Behavioral Biology of Killer Whales, pp. 211-49. New York: Alan R. Liss.

Reeves, R. R., and E. Mitchell (1988) “Distribution and Seasonality of Killer Whales in the Eastern Canadian Arctic.” In J. Sigurjónsson and S. Leatherwood, eds., North Atlantic Killer Whales, pp. 136–60. Rit Fiskideildar (Journal of the Marine Research Institute, Reykjavik), vol. 11. Reykjavik: Hafrannsók-nastofnunin.

*Rose, N.A. (1992) “The Social Dynamics of Male Killer Whales, Orcinus orca, in Johnstone Strait, British Columbia.” Ph.D. thesis, University of California–Santa Cruz.

*Saulitis, E. L. (1993) “The Behavior and Vocalizations of the ‘AT’ Group of Killer Whales (Orcinus orca) in Prince William Sound, Alaska.” Master’s thesis, University of Alaska.

*Utrecht, W. L. van (1960) “Notat om den hermafroditte spermhval/Note on the ‘Hermaphrodite Sperm Whale.’” Norsk Hvalfangst-Tidende 49:520.

For eight months of the year—during the migration and summering periods—Gray Whales generally travel and socialize in sex-segregated groups (sometimes known as PODS), while for the remaining time the two sexes are together. Gray Whales have one of the longest migration routes of any mammal: they spend their summers feeding in northern waters, while in the fall they head south on a four-month journey to the mangrove lagoons off Baja California where they mate and their calves are born, only to return to their northern waters in the early spring. A few populations of Gray Whales are nonmigratory, remaining year-round in northern waters.

Behavioral Expression: Male homosexual interactions among Gray Whales occur frequently in the northern summering waters and during the northward migration. Sexual and affectionate activities occur close to the surface of the water in long sessions lasting anywhere from 30 minutes to more than an hour and a half. Often more than two males are involved, sometimes as many as four or five. The whales begin by rolling around each other and onto their sides, with much splashing of water, flailing of fins and flukes at the surface, and occasional slapping of the surface and blowing; sometimes two males rise out of the water several feet in a throat-to-throat position. The whales rub their bellies together and position themselves so that their genital areas are in contact, and usually one or more has an arching, erect or semi-erect penis (which is a distinctive light pink in color and may be three to five feet in length and a foot in circumference at its base). Often two or more males intertwine their penises above the water surface, or one male may lay his erect penis on another male’s belly or perhaps nudge the other’s penis with his head. Female homosexual interactions may also occur.

Gray Whales also frequently form same-sex companionships (pairs and trios) that travel and feed together throughout the summer (without necessarily engaging in sexual activity with one another). They swim in an intimate side-by-side position, often with their side fins touching, and travel back and forth along the length of coastal inlets for hours at a time, apparently with no particular purpose other than to be together. Such companions also perform synchronized blowing and diving maneuvers, including feeding and BREACHING (an acrobatic leap two-thirds out of the water, landing with a dramatic splash on their sides or backs). Two whales also often roll over and under each other, rubbing bellies. Both short-term and long-term (recurring) pair- and trio-bonds occur: some last only for a few hours or days, with the whales changing partners several times over the summer; other companionships endure from year to year.

Frequency: Homosexual activity is fairly common in Gray Whales outside the breeding season, and can be seen perhaps as often as five or six times a month in the early spring in some populations. Actual frequencies may be higher, since much sexual activity probably occurs underwater or in locations that are otherwise difficult to observe. At least a quarter of all companion pairs and trios are same-sex.

Orientation: The majority of male Gray Whales are probably bisexual, interacting primarily with each other on the migrations and during the summer in the north, and interacting heterosexually in the calving waters in the south.

Migration in Gray Whales involves a lot more than travel: feeding, nursing, and sexual activity all take place during the journey. Migrating pods are separated according to the sex, age, and reproductive status of the whales: on the northward migration, for example, newly pregnant females usually leave first, then adult males, followed by nonovulating and immature females, immature males, and lastly females with new calves. Male Gray Whales also have a distinct seasonal sexual cycle related to sperm production: during the northward migration and the summer months, their testes are essentially inactive, producing little or no sperm; on the southward migration sperm production resumes and peaks in late fall and early winter in preparation for heterosexual breeding. Consequently, for two-thirds of the year, male Gray Whales are nonfertile, even though they sometimes engage in heterosexual copulation during these times. Combined with the female sexual cycle (with its infertile period in the spring and summer) and the fact that sexual interactions outside the mating season may involve groups of whales (not all of whom copulate), this means that a significant portion of heterosexual activity is nonreproductive. Furthermore, heterosexual courtship and copulation during the mating season also sometimes involves groups of up to 18 whales interacting at the same time, and both males and females mate with multiple partners. During the actual mating act, trios consisting of two males and one female are sometimes involved: one male is a “helper” who does not interact sexually with the female, but seems instead to assist the other two to align their bodies and maintain their position during copulation. Females usually breed only every other year, and some wait two years between calves.

*asterisked references discuss homosexuality/transgender

Baldridge, A. (1974) “Migrant Gray Whales with Calves and Sexual Behavior of Gray Whales in the Monterey Area of Central California, 1967–1973.” Fishery Bulletin, U.S. 72:615–18.

Darling, J. D. (1984) “Gray Whales Off Vancouver Island, British Columbia.” In M. L. Jones, S. L. Swartz, and S. Leatherwood, eds., The Gray Whale, Eschrichtius robustus, pp. 267–87. Orlando: Academic Press.

*———(1978) “Aspects of the Behavior and Ecology of Vancouver Island Gray Whales, Eschrichtius glaucus Cope.” Master’s thesis, University of Victoria.

*———(1977) “The Vancouver Island Gray Whales.” Waters: Journal of the Vancouver Public Aquarium 2:4–19.

Fay, F. H. (1963) “Unusual Behavor of Gray Whales in Summer.” Psychologische Forschung 27:175–76.

Hatler, D. F., and J. D. Darling (1974) “Recent Observations of the Gray Whale in British Columbia.” Canadian Field-Naturalist 88:449–59.

Houck, W. J. (1962) “Possible Mating of Gray Whales on the Northern California Coast.” Murrelet 43:54.

Rice, D. W., and A. A. Wolman (1971) The Life History and Ecology of the Gray Whale (Eschrichtius robustus). American Society of Mammalogists Special Publication no. 3. Stillwater, Okla.: American Society of Mammalogists.

Samaras, W. E (1974) “Reproductive Behavior of the Gray Whale, Eschrichtius robustus, in Baja, California.” Bulletin of the Southern California Academy of Sciences 73(2):57–64.

Sauer, E. G. F. (1963) “Courtship and Copulation of the Gray Whale in the Bering Sea at St. Lawrence Island, Alaska.” Psychologische Forschung 27:157–74.

Swartz, S. L. (1986) “Demography, Migration, and Behavior of Gray Whales Eschrichtius robustus (Lilljeborg, 1861) in San Ignacio Lagoon, Baja California Sur, Mexico and in Their Winter Range.” Ph.D. thesis, University of California–Santa Cruz.

Bowhead Whales socialize and travel in small groups of 2–7 animals as well as larger herds of 50–60 individuals; many animals are solitary as well. During much of the year—e.g., the spring migrations, and the socializing and feeding periods of summer and early fall—males and females (as well as different age groups) generally associate separately from each other. Right Whales may form aggregations of 100 or more individuals, although most social interactions occur during the mating period.

Behavioral Expression: Intensive sexual encounters between male Bowhead Whales take place in shallow waters, involving three to six males at a time. Amid much splashing and churning of water, the males roll over each other with erect (unsheathed) penises, caress one another, slap the surface of the water with their tails or flippers, chase each other, and perform TAIL LOFTS, in which the tail is lifted high above the water while the whale sinks vertically down. Generally there is one central whale that the others are trying to copulate with, although this whale often rolls belly up in the water, perhaps attempting to avoid their advances (similar to the behavior of females during heterosexual mating activity). Nevertheless, a male Bowhead sometimes inserts his penis into the genital slit of another male. Sessions of homosexual activity can last for 40 minutes or more, during which males often produce loud and complex vocalizations that resemble roars, screams, or trumpetings. Both male and female Right Whales also engage in homosexual activity, involving such behaviors as caressing, rolling and pushing, and flipper and fluke slaps.

Bowhead Whales also have a relatively high incidence of intersexual or hermaphrodite individuals with female external genitalia and mammary glands combined with male chromosomes and internal sexual organs such as testes (which are contained within the body cavity in this species, as in other cetaceans).

Frequency: Homosexual activity is characteristic of certain times of the year: in Bowheads, it generally occurs during the late summer and fall, while in Right Whales, it occurs early in the season for females, and late in the season for males. Beyond this, it is difficult to quantify the frequency of same-sex interactions. Among Bowheads, social activity is common during the fall, and about 40 percent of all socializing groups include three or more whales (the configuration typical of sexual interactions). Although the exact percentage of these interactions that are homosexual is not known, in two out of three such groups in which the sexes of all the animals could be determined, the sexual activity involved only males. It is possible, therefore, that a significant proportion of fall sexual activity—perhaps even a majority—is homosexual. Intersexuality in Bowheads is relatively common, occurring in about 1 in 4,000 individuals (compared with a rate of 1 in 62,400 humans for the same type of intersexuality).

Orientation: In Bowhead Whales, homosexual behavior appears to be typical of adolescent or younger adult males, so it may be that individuals engage in sequential or chronological bisexuality over their lives, with an initial period of homosexuality followed by heterosexuality. This is speculative, however, because the life histories of individual whales have not been tracked. In Right Whales, homosexual behavior is not restricted to younger animals, but in fact occurs among whales of all ages; the extent of heterosexual activities (if any) of such individuals are not fully known.

Because Bowhead and Right Whales generally mate throughout the year—and in particular outside of the female’s fertilizable period—a large proportion of heterosexual activity is nonprocreative. In both species, heterosexual copulation usually involves a group of several males trying to mate with one female, who often tries to escape their attentions. At times, the interaction can become violent: groups of male Right Whales searching for females have been described as “rape gangs,” and sometimes two or more males cooperate in forcing a female underwater so that they can take turns mating with her. In some cases, calves get caught in the middle of a heterosexual mating attempt and are hit, crushed, and perhaps even killed. Females of these two species generally do not breed every year. In Right Whales, for example, five or more years may elapse between calves, with the result that sometimes less than half of the adult females in an area are breeding.

Intersexuality or transgender has also been reported among Fin Whales (Balaenoptera physalus): one individual, for example, had both male and female reproductive organs, including a uterus, vagina, elongated clitoris, and testes.

*asterisked references discuss homosexuality/transgender

*Bannister, J. L. (1963) “An Intersexual Fin Whale Balaenoptera physalus (L.) from South Georgia.” Proceedings of the Zoological Society of London 141:811–22.

Clark, C. W. (1983) “Acoustic Communication and Behavior of the Southern Right Whale (Eubalaena australis ).” In R. S. Payne, ed., Communication and Behavior of Whales, pp. 163–98. American Association for the Advancement of Science Selected Symposium 76. Boulder: Westview Press.

Everitt, R. D., and B. D. Krogman (1979) “Sexual Behavior of Bowhead Whales Observed Off the North Coast of Alaska.” Arctic 32:277–80.

Finley, K. J. (1990) “Isabella Bay, Baffin Island, an Important Historical and Present-Day Concentration Area for the Endangered Bowhead Whale (Balaena mysticetus) of the Eastern Canadian Arctic.” Arctic 43:137–52.

*Koski, W. R., R. A. Davis, G.W. Miller, and D. E. Withrow (1993) “Reproduction.” In J. J. Burns, J. J. Montague, and C. J. Cowles, eds., The Bowhead Whale, pp. 239–74. Lawrence, Kans.: Society for Marine Mammalogy.

*Moore, S. E., and R. R. Reeves (1993) “Distribution and Movement.” In J. J. Burns, J. J. Montague, and C. J. Cowles, eds., The Bowhead Whale, pp. 313–86. Lawrence, Kans.: Society for Marine Mammalogy.

*Östman, J. (1991) “Changes in Aggressive and Sexual Behavior Between Two Male Bottlenose Dolphins (Tursiops truncatus) in a Captive Colony.” In K. Pryor and K. S. Norris, eds., Dolphin Societies: Discoveries and Puzzles, pp. 304—17. Berkeley: University of California Press.

Payne, R. (1995) Among Whales. New York: Scribner.

*Richardson, W. J., and K. J. Finley (1989) Comparison of Behavior of Bowhead Whales of the Davis Strait and Bering/Beaufort Stocks. Report from LGL Ltd., King City, Ontario, for U.S. Minerals Management Service, Herndon, Va.; OCS Study MMS 88–0056, NTIS no. PB89–195556/AS. Springfield, Va.: National Technical Information Service.

*Richardson, W. J., K. J. Finley, G.W. Miller, R. A. Davis, and W. R. Koski (1995) “Feeding, Social, and Migration Behavior of Bowhead Whales, Balaena mysticetus, in Baffin Bay vs. the Beaufort Sea—Regions with Different Amounts of Human Activity.” Marine Mammal Science 11:1–45.

Saayman, G. S., and C. K. Tayler (1973) “Some Behavior Patterns of the Southern Right Whale, Eubalaena australis.” Zeitschrift für Säugetierkunde 38:172–83.

*Tarpley, R. J., G. H. Jarrell, J. C. George, J. Cubbage, and G. G. Stott (1995) “Male Pseudohermaphroditism in the Bowhead Whale, Balaena mysticetus.” Journal of Mammalogy 76:1267–75.

*Würsig, B., and C. Clark (1993) “Behavior.” In J. J. Burns, J. J. Montague, and C. J. Cowles, eds., The Bowhead Whale, pp. 157-99. Lawrence, Kans.: Society for Marine Mammalogy.

*Würsig, B., J. Guerrero, and G. Silber (1993) “Social and Sexual Behavior of Bowhead Whales in Fall in the Western Arctic: A Re-examination of Seasonal Trends.” Marine Mammal Science 9:103–11.

SEALS AND MANATEES

Gray Seals are highly gregarious, congregating in large colonies for mating and molting, and in large groups to feed. In some populations the mating system is primarily polygynous, meaning that males mate with multiple partners, do not form heterosexual pair-bonds, and do not participate in parenting. However, some individuals in these areas are “monogamous” in that they mate with the same partner year after year, while in other populations the majority of individuals mate with only one partner but not necessarily the same one each year. Northern Elephant Seals are more solitary when at sea, although they form large breeding and molting aggregations in traditional areas known as ROOKERIES and also have a polygynous mating system. Harbor Seals generally congregate in mixed-sex groups on land, anywhere from a dozen to several thousand animals; they often mate in the water, however, and appear to have a polygynous mating system as well.

Behavioral Expression: During the nonbreeding season, both Gray Seal and Northern Elephant Seal bulls engage in homosexual activity. Gray Seals come ashore to molt their fur, gathering in groups of up to 150 animals, no more than half a dozen of which are females. Those males who have completed their molt often roll around in pairs near the water and mount each other; bulls of all ages participate in this activity. Both adolescent and younger adult Northern Elephant Seal bulls also engage in homosexual mounting during the molt period. This occurs in shallow waters near the shore, often as a part of extended bouts of harmless play-fighting among clusters of males. Prior to and during the mating season, this activity continues among adolescent males, though it is usually no longer aquatic. Adolescent males often spend time in male-only areas that are separate from the breeding grounds. Males are attracted to the play-fighting and mounting activity in these areas and may travel up to 100 yards through the rookery to join in. Adult bulls do not participate in this activity. However, they do sometimes mount younger adolescent and juvenile males (two to four years old). Typically the older male approaches a younger male at rest, moving up alongside him and sometimes placing his front flipper over his back in the position characteristic of heterosexual copulations. Usually the younger male struggles to escape, and the mounter may try to subdue him by pressing or bouncing his neck down on top of him or biting his neck. The older male may have an erection and attempt to penetrate the younger male, but he rarely if ever succeeds. Although they prefer juveniles or adolescents, a few bulls also try to copulate with much younger animals, such as weaned pups of both sexes (who strongly resist their advances).

Homosexual activity is also prevalent in male Harbor Seals in the form of PAIR-ROLLING: two males embrace and mount each other in the water, continuously twisting and writhing about one another while maintaining full body contact. Rolling can become quite vigorous as the two animals spiral synchronously underwater and at the surface (often in a vertical position), sometimes gently mouthing or biting each other’s neck, chasing each other’s flippers, yelping and snarling, blowing streams of bubbles underwater, or slapping the surface of the water. One male usually has an erection, and the bout of courtship rolling typically ends when he mounts the other male, grasping him from behind and maintaining this position for up to 3 minutes (sometimes sinking to the bottom in shallower waters). The two males may also take turns mounting each other. Heterosexual copulations, in contrast, can occur both in the water and on land; they are not usually accompanied by pair-rolling and can last for up to 15 minutes. Although males of all ages engage in pair-rolling, most participants are adults (sexually mature individuals over six years old) or adolescents.

Same-sex courtship or sexual behavior is not found among females in these species, but two cow Seals occasionally coparent a pup. In Northern Elephant Seals, for example, two females who have each lost their own pup sometimes adopt an orphan and raise it together, or (more commonly) a cow who has lost her pup associates with a mother and shares parenting duties with her, including nursing the pup.

Finally, some adolescent Northern Elephant Seal males are transvestite, acting and looking like females. They have the body proportions of cow Seals, and they also deliberately pull in their noses so that they resemble females (who do not have the enlarged snouts that bulls do) and keep their heads low so as not to attract attention. Moving stealthily through the breeding grounds, these younger males try to copulate with females, who, nevertheless, are usually not fooled by their attempts to disguise themselves and usually do not allow them to mate. However, because most adult males are not able to mate with females, some transvestite males are actually more successful at breeding than non-transvestite males.

Frequency: Homosexual activity occurs frequently in Harbor Seals during the late spring, summer, and fall (except during the pupping season). In one two-month study period, for example, pair-rolling between males occurred daily and in total nearly 285 same-sex rolling pairs were observed (during the same period, no heterosexual matings were seen). Homosexual behavior is also common among male Gray Seals during the molting period, less frequent among Elephant Seal bulls (though it occurs at more times of the year in the latter species). Among females, approximately 2 percent of Elephant Seal adoptive families involve two pupless females coparenting orphaned pups, and another 14 percent involve one female sharing the care of a pup with its mother. Overall, these two-mother families probably represent about 2–3 percent of all families (the remainder are single-mother).

Orientation: Male Gray Seals exhibit seasonal bisexuality: during the molting period, many bulls participate in preferential homosexual activity—generally ignoring any females present in the herd—while during the mating season heterosexual behavior is the norm. However, only about a third of older males actually copulate with females, while less than 2 percent of younger males (up to eight years old) regularly have access to females. Thus, many bulls probably engage exclusively in homosexual activity for at least part of their lives. Younger adolescent male Elephant Seals—who make up 25–55 percent of the male population—may participate primarily in homosexual mounting, since few actually mate with females. At the other extreme, the highest-ranking bulls are probably exclusively heterosexual, since their attentions are usually directed toward mating (often with hundreds of females each season). Some older adolescent males (40–55 percent of the population) or younger adults may be bisexual, mounting both males and females. However, since less than 9 percent of all males ever mate with females during their lifetime, and less than half of those males surviving to breeding age ever mate, a large number may participate only in same-sex activity (as in Gray Seals). Bulls who mount pups—only a fraction of the male population—do so with equal frequency on both male and female pups. In Harbor Seals, males participate in pair-rolling activity with one another even in the presence of receptive females and generally do so for several months each year (heterosexual mating is usually restricted to a shorter period, perhaps a month or so). Similar patterns of sexual orientation among different age classes probably occur in this species as in the other two.

Gray, Harbor, and Northern Elephant Seals engage in a wide variety of nonprocreative heterosexual behaviors. Sexual activity during pregnancy is not uncommon. When female Gray Seals come ashore just before their pups are born, for example, they often participate in heterosexual copulation and other sexual interactions with males, including REVERSE mountings (in which they mount the male rather than vice versa). Male Northern Elephant Seals also mate with pregnant females, including cows who are leaving the breeding grounds after having already been inseminated. Gray and Harbor Seals sometimes copulate outside of the mating season when fertilization is impossible—not only because the females are pregnant, but because (in Grays) males have their own sexual cycle that renders their testes inactive at that time. Heterosexual matings also occasionally occur between these two species. In addition, females in all three species may copulate with multiple male partners.

As noted above, some male Northern Elephant Seals try to copulate with weaned pups—about half of all pups are subjected to such forced mating or rape attempts, which they usually violently resist. In some cases the pups are severely injured by the bulls, with deep gashes and punctures from neck bites. Aggressive sexual behavior by bulls is the leading cause of mortality among pups on the breeding grounds, accounting for the deaths of about 1 in 200 pups each year. Male Northern Elephant Seals also sometimes aggressively mount pups of other species such as Harbor Seals. Similar aggression, violence, and attempted rape—sometimes lethal—is also directed by bulls toward adult females and adolescents. During mating, male Northern Elephant Seals routinely bite, pin down, and slam the full weight of their bodies against females (bulls are 5–11 times heavier than females). A female may be pursued by groups of males as she leaves the rookery, sometimes being raped three to seven times as she tries to escape. Some bulls even try to mate with dead females that have been killed during such attacks (and even with dead seals of other species). Mating in Harbor Seals may also involve aggressive attacks by males, female refusal, and even “gangs” of two or three males forcibly copulating with a female. In addition, Gray and Harbor Seal pups are sometimes killed by adults (accounting for about 7 percent of Gray Seal pup deaths), while roughly 6 percent of Harbor Seal pups are abandoned by their mothers shortly after birth.

For much of the year, the two sexes lead largely segregated lives: Northern Elephant Seal males and females, for example, each embark on their own epic migratory journeys twice a year. Males travel farther north to Alaska while females journey out into the central Pacific, remaining separate for up to 300 days as they traverse more than 13,000 miles in their double migrations. Male Gray Seals are at sea (or molting on land) essentially separate from females for nine to ten months of the year. This segregation is facilitated in part by the phenomenon of DELAYED IMPLANTATION, in which a female’s fertilized embryo remains in “suspended animation” for three to four months, extending the duration of the pregnancy to eleven or more months. Even during the breeding season, many males do not copulate or reproduce: usually only 14–35 percent of the males present on the breeding grounds mate each season. Likewise, more than 90 percent of male Elephant Seals never copulate during their entire lives (most delay breeding until fairly late and simply perish before reaching the age when reproduction usually begins). Because a small number of individuals often monopolize mating opportunities, some populations may experience high levels of inbreeding. In addition, about 20 percent of females skip breeding each year in some populations.

Separation of the sexes continues through pup-rearing: like most polygamous animals, male Seals do not participate in any parenting duties. Females, however, engage in an assortment of fostering activities, often after they have lost their own pup (although some take care of other pups in addition to their own). More than half of all Northern Elephant Seal pups become separated from their mothers each season, and about 18 percent of all females adopt pups. Besides the female coparenting arrangements mentioned above, many females adopt orphan pups on their own, some female Elephant Seals nurse several orphans at once, while others nurse already weaned pups (who become bloated from the extra milk, turning into gigantic “superweaners,” as they are called). Some females even try to “kidnap” or steal pups away from their own mothers, and females who have not lost their own pup often threaten, attack, and even kill stray pups. As many as a quarter to three-quarters of female Gray Seals and 10 percent of female Harbor Seals participate in foster-parenting in some populations.

Pairs of female Spotted or Larga Seals (Phoca largha) occasionally coparent their pups together, even sharing in nursing their offspring. Male Sea Otters (Enhydra lutris) have been observed clasping and mounting other males (in the water) in the position usually seen during heterosexual matings. Male Sea Otters also sometimes mount and attempt to mate with Seals, including Harbor Seals and Northern Elephant Seals, and some of these interactions may be same-sex.

*asterisked references discuss homosexuality/transgender

Allen, S. G. (1985) “Mating Behavior in the Harbor Seal.” Marine Mammal Science 1:84–87.

Amos, B., S. Twiss, P. Pomeroy, and S. Anderson (1995) “Evidence for Mate Fidelity in the Gray Seal.” Science 268:1897–99.

Anderson, S. S. (1991) “Gray Seal, Halichoerus grypus.” In G. B. Corbet and S. Harris, eds., The Handbook of British Mammals, pp. 471–80. Oxford: Blackwell Scientific Publications.

Anderson, S. S., and M. A. Fedak (1985) “Gray Seal Males: Energetic and Behavioral Links Between Size and Sexual Success.” Animal Behavior 33:829–38.

*Backhouse, K. M. (1960) “The Gray Seal (Halichoerus grypus) Outside the Breeding Season: A Preliminary Report.” Mammalia 24:307–12.

———(1954) “The Gray Seal.” University of Durham Medical Gazette 48:9–16.

*Backhouse, K. M., and H. R. Hewer (1957) “Behavior of the Gray Seal (Halichoerus grypus Fab.) in the Spring.” Proceedings of the Zoological Society of London 129:450.

Baker, J. R. (1984) “Mortality and Morbidity in Gray Seal Pups (Halichoerus grypus).” Journal of Zoology, London 203:23–48.

Bishop, R. H. (1967) “Reproduction, Age Determination, and Behavior of the Harbor Seal, Phoca vitulina L. in the Gulf of Alaska.” Master’s thesis, University of Alaska.

Boness, D. J., D. Bowen, S. J. Iverson, and O. T. Oftedal (1992) “Influence of Storms and Maternal Size on Mother-Pup Separations and Fostering in the Harbor Seal, Phoca vitulina.” Canadian Journal of Zoology 70:1640–44.

Boness, D. J., and H. James (1979) “Reproductive Behavior of the Gray Seal (Halichoerus grypus) on Sable Island, Nova Scotia.” Journal of Zoology, London 188:477–500.

Burton, R. W., S. S. Anderson, and C. F. Summers (1975) “Perinatal Activities in the Gray Seal (Halichoerus grypus).” Journal of Zoology, London 177:197–201.

Coulson, J. C., and G. Hickling (1964) “The Breeding Biology of the Gray Seal, Halichoerus grypus (Fab.), on the Farne Islands, Northumberland.” Journal of Animal Ecology 33:485-512.

*Deutsch, C. J. (1990) “Behavioral and Energetic Aspects of Reproductive Effort of Male Northern Elephant Seals (Mirounga angustirostris).” Ph.D. thesis, University of California–Santa Cruz.

*Hatfield, B. B., R. J. Jameson, T. G. Murphey, and D. D. Woodard (1994) “Atypical Interactions Between Male Southern Sea Otters and Pinnipeds.” Marine Mammal Science 10:111–14.

Hewer, H. R. (1960) “Behavior of the Gray Seal (Halichoerus grypus Fab.) in the Breeding Season.” Mammalia 24:400–21.

Hewer, H. R., and K. M. Backhouse (1960) “A Preliminary Account of a Colony of Gray Seals, Halichoerus grypus (Fab.) in the Southern Inner Hebrides.” Proceedings of the Zoological Society of London 134:157–95.

Hoover, A. A. (1983) “Behavior and Ecology of Harbor Seals (Phoca vitulina richardsi) Inhabiting Glacial Ice in Aialik Bay, Alaska.” Master’s thesis, University of Alaska.

*Johnson, B.W. (1976) “Studies on the Northernmost Colonies of Pacific Harbor Seals, Phoca vitulina richardsi, in the Eastern Bering Sea.” Unpublished report, University of Alaska Institute of Marine Science and Alaska Department of Fish and Game; 67 pp. (available at National Marine Mammal Laboratory Library, Seattle, Wash.).

*———(1974) “Otter Island Harbor Seals: A Preliminary Report.” Unpublished report, University of Alaska Institute of Marine Science and Alaska Department of Fish and Game; 20 pp. (available at National Marine Mammal Laboratory Library, Seattle, Wash.).

*Johnson, B. W., and P. Johnson (1977) “Mating Behavior in Harbor Seals?” Proceedings (Abstracts) of the Conference on the Biology of Marine Mammals (San Diego) 2:30.

Kroll, A. M. (1993) “Haul Out Patterns and Behavior of Harbor Seals, Phoca vitulina, During the Breeding Season at Protection Island, Washington.” Master’s thesis, University of Washington.

*Le Boeuf, B. J. (1974) “Male-Male Competition and Reproductive Success in Elephant Seals.” American Zoologist 14:163–76.

———(1972) “Sexual Behavior in the Northern Elephant Seal, Mirounga angustirostris.” Behavior 41: 1–26.

Le Boeuf, B. J., and R. M. Laws (eds.) (1994) Elephant Seals: Population Ecology, Behavior, and Physiology. Berkeley: University of California Press.

Le Boeuf, B. J., and S. Mesnick (1991) “Sexual Behavior of Male Northern Elephant Seals: I. Lethal Injuries to Adult Females.” Behavior 116:143–62.

Le Boeuf, B. J., and J. Reiter (1988) “Lifetime Reproductive Success in Northern Elephant Seals.” In T. H. Clutton-Brock, ed., Reproductive Success: Studies of Individual Variation in Contrasting Breeding Systems, pp. 344–62. Chicago: University of Chicago Press.

Mortenson, J., and M. Follis (1997) “Northern Elephant Seal (Mirounga angustirostris) Aggression on Harbor Seal (Phoca vitulina) Pups.” Marine Mammal Science 13:526-30.

Perry, E. A., and W. Amos (1998) “Genetic and Behavioral Evidence That Harbor Seal (Phoca vitulina) Females May Mate with Multipile Males.” Marine Mammal Science 14:178–82.

Riedman, M. L. (1990) The Pinnipeds: Seals, Sea Lions, and Walruses. Berkeley: University of California Press.

*Riedman, M. L., and B. J. Le Boeuf (1982) “Mother-Pup Separation and Adoption in Northern Elephant Seals.” Behavioral Ecology and Sociobiology 11:203–15.

*Rose, N. A., C. J. Deutsch, and B. J. Le Boeuf (1991) “Sexual Behavior of Male Northern Elephant Seals: III. The Mounting of Weaned Pups.” Behavior 119:171–92.

Smith, E. A. (1968) “Adoptive Suckling in the Gray Seal.” Nature 217:762–63.

Stewart, B. S., and R. L. DeLong (1995) “Double Migrations of the Northern Elephant Seal, Mirounga angustirostris.” Journal of Mammalogy 76:196—205.

Sullivan, R. M. (1981) “Aquatic Displays and Interactions in Harbor Seals, Phoca vitulina, with Comments on Mating Systems.” Journal of Mammalogy 62:825–31.

Thompson, P. (1988) “Timing of Mating in the Common Seal (Phoca vitulina).” Mammal Review 18:105–12.

Tinker, M. T., K. M. Kovacs, and M. O. Hammill (1995) “The Reproductive Behavior and Energetics of Male Gray Seals (Halichoerus grypus) Breeding on a Land-Fast Ice Substrate.” Behavioral Ecology and Sociobiology 36:159–70.

Venables, U. M., and L. S. V. Venables (1959) “Vernal Coition of the Seal Phoca vitulina in Shetland,” Proceedings of the Zoological Society of London 132:665–69.

———(1957) “Mating Behavior of the Seal Phoca vitulina in Shetland.” Proceedings of the Zoological Society of London 128:387–96.

Wilson, S. C. (1975) “Attempted Mating Between a Male Gray Seal and Female Harbor Seals.” Journal of Mammalogy 56:531–34.

During the breeding season, females of each of these species aggregate into groups among which a smaller number of males are distributed. This organization has been mistakenly interpreted as a “harem” structure, when in fact males have little control over the movements of the females, whose grouping is often the result of seeking each other out while simultaneously avoiding males. In the Northern Fur Seal, nonbreeding animals and juveniles gather on islands separate from the breeding areas; nonbreeding groups also occur in the other two species. Outside of the mating season, Australian and New Zealand Sea Lions form smaller mixed-sex groups, while Northern Fur Seals are oceangoing, relatively solitary, and sex-segregated during the fall, winter, and spring.

Behavioral Expression: In Australian and New Zealand Sea Lions, homosexual mounting is common: one male mounts the other from behind (as in heterosexual copulation) and makes pelvic thrusts against the other male. Homosexual copulation can take place either on the beach or in the surf (the latter especially among older males). All age groups participate, although there is often an age difference between the two males, with the younger male typically mounting the older one (especially in New Zealand Sea Lions). Among younger males, homosexual behavior is often a component of play-fighting, in which the two males stand chest to chest and push against one another, with each trying to grab the other’s neck in his mouth. Female Australian Sea Lions also occasionally mount one another, but lesbian mounting is more common in Northern Fur Seals. During the mating season, one female sometimes copulates with another by mounting her and performing pelvic thrusts; the mounted female often facilitates the homosexual mount by arching her back and extending her flippers, thereby making her genital region more accessible to the other female.

Frequency: Homosexual behavior occurs fairly frequently in Australian and New Zealand Sea Lions and occasionally in Northern Fur Seals.

Orientation: In Australian and New Zealand Sea Lions, younger males that do not associate with female groups may engage exclusively in homosexual activity, since many such individuals (which make up 81 percent of the New Zealand, and 33 percent of the Australian, male population) do not mate heterosexually. In New Zealand Sea Lions, adult breeding males also sometimes participate in homosexual mounting, making them bisexual, whereas in Australian Sea Lions, adult breeding males are exclusively heterosexual. In Northern Fur Seals, all females that participate in lesbian mounting are also active heterosexually, since they also mate with males. In fact, nearly all females involved in homosexual activity are mothers, although not all mothers engage in homosexual mounting. However, the amount of homosexual activity that an individual female participates in may be equal to or greater than her heterosexual activity, since females usually mate with a male only once during the entire breeding season.

In all three of these eared seals, significant proportions of the population do not breed. As noted above, more than 80 percent of New Zealand Sea Lion adult males, and a third of Australian Sea Lion males, do not participate in heterosexual mating. In Northern Fur Seals most males younger than nine years old do not mate because they cannot compete with older males for access to females, while most breeding males actually participate in reproduction for only a single season out of their entire lives. The average male copulates with females only 3–4 times during his life, and many males never do so. In addition, 8–17 percent of females on the breeding grounds do not get pregnant each year, and females generally reproduce only once every five years or so. In fact, nearly 60 percent of the total population consists of nonbreeders that do not even attempt to reproduce. Australian Sea Lions are unusual among mammals in having an exceptionally long or “supra-annual” breeding cycle, 17–18 months from mating to birth (most mammals complete the cycle in less than a year, allowing them to breed annually). Part of the reason for this extended cycle is because of the phenomenon known as DELAYED IMPLANTATION (also found in other seals), in which the fertilized egg fails to develop and instead remains in “suspended animation”—in this species, for as long as eight or nine months. In addition, late-term abortions are relatively common in Australian Sea Lions. Implantation in Northern Fur Seals is delayed for four to five months, but about 11 percent of embryos fail to implant or are aborted or reabsorbed.

In addition to this separation between insemination and fetal development, there is notable spatial and temporal segregation of the sexes in these species. In Northern Fur Seals, males and females go separate ways once the mating season is over: females range widely over the north Pacific Ocean while males remain in the Bering Sea. Since males and females interact for only two months out of the year, this means that the majority of their lives are spent apart from each other. Furthermore, the two sexes are often antagonistic when they are together. Male Northern Fur Seals sometimes try to prevent females from leaving their territory by throwing them bodily and flipping them into the air. Two males may also try to claim the same female by grabbing her with their jaws—sometimes while she is actually giving birth—causing severe lacerations or even death in the resulting tug-of-war. In Australian Sea Lions, “gangs” of younger males roam through the colony, sexually harassing females and attacking those that try to get away. A male New Zealand Sea Lion was once observed trying to copulate with a dead female New Zealand fur seal (Arctocephalus forsteri), which he may have killed during a previous mating attempt. Sexual interactions between Northern Fur Seals and California sea lions (Zalophus californianus) also occur, and male Northern Fur Seals have also been known to attempt forcible copulation with pups of their own species. In addition, male (and occasionally female) Australian Sea Lions often savagely attack pups, shaking, tossing, and biting them. Death from the resulting injuries is the primary cause of mortality for pups on land, accounting for nearly a fifth of all pup deaths in this species. About 17 percent of all Northern Fur Seal pup fatalities are due to attacks from adults (usually females).

In spite of these severe obstacles facing adult females and young seals, a number of innovative shared parenting or “day-care” arrangements have developed in these species. In Australian Sea Lions, females take turns watching over and defending a group of pups. In Northern Fur Seals, pups gather in nursery groups or PODS for protection while their mothers are away at sea—which is most of the time, since mothers usually spend only one day ashore each week and may be gone for up to 16 days at a time. Female Australian Sea Lions that have lost their own pup also sometimes try to abduct another female’s youngster.

*asterisked references discuss homosexuality/transgender

*Bartholomew, G. A. (1959) “Mother-Young Relations and the Maturation of Pup Behavior in the Alaska Fur Seal.” Animal Behavior 7:163–71.

Bartholomew, G. A., and P. G. Hoel (1953) “Reproductive Behavior of the Alaska Fur Seal, Callorhinus ursinus.” Journal of Mammalogy 34:417–36.

Gales, N. J., P. D. Shaughnessy, and T. E. Dennis (1994) “Distribution, Abundance, and Breeding Cycle of the Australian Sea Lion Neophoca cinerea (Mammalia: Pinnipedia).” Journal of Zoology, London 234:353–70.

*Gentry, R. L. (1998) Behavior and Ecology of the Northern Fur Seal. Princeton: Princeton University Press.

———(1981) “Northern Fur Seal, Callorhinus ursinus (Linnaeus, 1758).” In S. H. Ridgway and R. J. Harrison, eds., Handbook of Marine Mammals, vol. 1, pp. 143–60. London: Academic Press.

Higgins, L. V. (1993) “The Nonannual, Nonseasonal Breeding Cycle of the Australian Sea Lion, Neophoca cinerea.” Journal of Mammalogy 74:270–74.

Higgins, L. V., and R. A. Tedman (1990) “Attacks on Pups by Male Australian Sea Lions, Neophoca cinerea, and the Effect on Pup Mortality.” Journal of Mammalogy 71:617–19.

Kenyon, K. W., and F. Wilke (1953) “Migration of the Northern Fur Seal, Callorhinus ursinus.” Journal of Mammalogy 34:86–89.

*Marlow, B. J. (1975) “The Comparative Behavior of the Australasian Sea Lions Neophoca cinerea and Phocarctos hookeri (Pinnipedia: Otariidae).” Mammalia 39:159–230.

———(1972) “Pup Abduction in the Australian Sea-lion, Neophoca cinerea:” Mammalia 36:161–65.

Miller, E. H., A. Ponce de Léon, and R. L. DeLong (1996) “Violent Interspecific Sexual Behavior by Male Sea Lions (Otariidae): Evolutionary and Phylogenetic Implications:” Marine Mammal Science 12:468–76.

Peterson, R. S. (1968) “Social Behavior in Pinnipeds with Particular Reference to the Northern Fur Seal.” In R. J. Harrison, R. C. Hubbard, R. S. Peterson, C. E. Rice, and R. J. Schusterman, eds., The Behavior and Physiology of Pinnipeds, pp. 3–53. New York: Appleton-Century-Crofts.

Walker, G. E., and J. K. Ling (1981) “New Zealand Sea Lion, Phocarctos hookeri (Gray, 1844)” and “Australian Sea Lion, Neophoca cinerea (Peron, 1816).” In S. H. Ridgway and R. J. Harrison, eds., Handbook of Marine Mammals, vol. 1, pp. 25–38, 99–118. London: Academic Press.

Wilson, G. J. (1979) “Hooker’s Sea Lions in Southern New Zealand.” New Zealand Journal of Marine and Freshwater Research 13:373–75.

York, A. E., and V. B. Scheffer (1997) “Timing of Implantation in the Northern Fur Seal, Callorhinus ursinus.” Journal of Mammalogy 78:675–83.

From January to March (the breeding season), Walruses congregate far from shore on and around pack ice, where heterosexual courtship and mating take place. The mating system is polygynous—males generally copulate with several different females without forming long-lasting heterosexual bonds. During the summer and early fall, males gather together in large aggregations numbering in the thousands, typically on islands that are used for this purpose year after year. These “haul-outs” are sex-segregated. When both males and females are present, they tend to occupy distinct areas; more typically, however, the haul-outs are entirely male, since females and their young migrate to the far north to spend the summer.

Behavioral Expression: In the shallow waters off the coast of the summer haul-out grounds, male Walruses engage in homosexual courtship, sexual, and affectionate activities. Pairs of males—sometimes as many as 50 animals at a time—float at the surface of the water by inflating special pouches in their throat, which act like the buoyant sacs in a life vest. While floating and swimming, the males—especially younger ones—rub their bodies against one another, clasp and embrace each other with their front flippers, touch noses, and loll together in groups. Males sometimes even sleep together in the water—pairs or groups of males float vertically at the surface (a posture known as BOTTLING), one behind the other, each male clasping the one in front of him in a “sleeping line.” Males also perform courtship displays for other males, employing a number of extraordinary behaviors and sounds that are also used in heterosexual courtship. Typically a younger male displays to an older one, and courting males often situate themselves in the water near a favorite cliff face, boulder, or rock formation at the water’s edge. The spectacular display consists of inflation of the throat pouches—often preceded by head bowing—interspersed with dives by one or both males, and an incredible series of vocalizations that form a courtship “song.” In homosexual encounters, at least three types of calls are used: KNOCKS, which are rapid, clicklike sounds resembling castanets, produced by “chattering” the cheek teeth underwater; a metallic BELL call, which is an eerie gonglike sound thought to be produced underwater by striking the throat pouches with the flippers to generate air pulses; and a short, piercing WHISTLE made through pursed lips when the Walrus resurfaces.

During same-sex courtship, sometimes one male rubs his erect, arm-sized penis with his front flipper. Overt sexual behavior between males takes the form of mounting (in the shallow water): one male clasps another with his flippers from behind, thrusting his pelvis and erect penis against the other male’s anal region. Younger males mount older ones and vice versa. Although most homosexual behavior is confined to the summer haul-outs, younger males sometimes also mount adults or other younger males during the breeding season. Groups of younger Walruses may crowd around an older male and roll on top of him; in addition, an adult male occasionally sings his courtship songs to a group of younger males or is accompanied by a younger attendant male while he sings. Often, his companion surfaces and dives in synchrony with him. This behavior, known as SHADOWING, occurs regardless of whether the adult is courting a female. In addition, male Walruses in captivity have been observed participating in cross-species homosexual encounters with male Gray Seals.

Frequency: Male Walruses engage in homosexual activities frequently during the summer haul-outs: approximately a quarter of all social interactions of males in the shallow waters involve same-sex affectionate, courtship, or sexual behaviors. On average, each male participates in such activity roughly five times per hour when in the water, and contact between males (including sexual and courtship behaviors) occupies about 3 percent of the overall time spent by males in the water. Up to 2 percent of the total male population (which may number more than 3,000) may be in the water at any one time engaging in homosexual activities. During the breeding season, up to a third of mounting activity may take place between younger males or between adult and younger males, and 2-19 percent of singing males have a younger male companion “shadowing” them.

Orientation: Because male Walruses achieve sexual maturity approximately four years before they actually participate in breeding, a sizable segment of the population is probably involved exclusively in homosexuality for a portion of their lives. Roughly 40-60 percent of all sexually mature males—those between the ages of 10 and 14—do not participate in heterosexual mating, and a large proportion of these males engage in homosexual activity. Most older males are seasonally bisexual, courting and copulating with females during the mating season and participating in same-sex activities during the summer and early fall; some, however, also engage in same-sex mounting and companionships during the breeding season.

As noted above, male Walruses experience a delay in their breeding careers, since most do not begin mating heterosexually until about 40 percent of their maximum life span is over. Once they do begin procreating, often only a small percentage of males actually copulates each year, perhaps as few as a quarter of all adult males. Among females, about half of the individuals over the age of 23 are nonbreeding, experiencing a postreproductive or “menopausal” period that may last for 7 or more years. Because of their long pregnancy (15-16 months) and nursing period (two years), most breeding-age females do not reproduce every year. One reason the pregnancy is so long is because of DELAYED IMPLANTATION: after mating, the fertilized egg fails to implant in the uterus and temporarily stops developing, remaining in “suspended animation” for four to five months. This results in an even longer period that the two sexes are separated. Although their social life is characterized by extensive sex segregation (see above), Walruses do sometimes copulate outside of the mating season. Heterosexual matings have been recorded in nearly all months of the spring and fall. Because males have a distinct yearly sexual cycle—their testes are essentially dormant except during January-March—most of this sexual activity is nonreproductive. Even during the mating season, Walruses participate in a variety of nonprocreative sexual behaviors. REVERSE mountings, in which the female clasps the male from behind and mounts him, occur in the water, and younger, sexually immature individuals also mount each other. Females have also been observed sucking their partner’s penis as well as kneading it to erection with their flippers prior to copulation (in captivity). Outside of the breeding season, males masturbate by stroking their penis with a front flipper, sometimes accompanied by knock sounds or STRUM calls (the latter sounding something like the strumming of fingers on a guitar or zither). In addition, interspecies heterosexual copulations with Gray Seals have been seen in captivity.

As in many other polygamous mammals, female Walruses generally raise their young on their own, occasionally supplemented with a number of alternative parenting arrangements. Unrelated females and males may assist in the care and protection of calves, nursery groups of youngsters sometimes play together while their mothers are occupied during the mating season, and orphaned calves are commonly adopted by other mothers or nonbreeding females. Occasionally, females even try to steal or “kidnap” calves from other females. Unfortunately, the lives of a calf and its mother are often endangered by male violence. Calves are sometimes gored by a male’s tusks, while mass tramplings may occur on haul-out sites—often triggered by belligerent Walrus bulls roaming through groups of females and their young. In some locations, such stampedes occur regularly, littering the beach with hundreds and even thousands of carcasses each year. Nearly a quarter of all fatalities are calves less than six months old, while 15 percent are aborted fetuses.

*asterisked references discuss homosexuality/transgender

Born, E.W., and L.Ø.Knutson (1997) “Haul-out and Diving Activity of Male Atlantic Walruses (Odobenus rosmarus rosmarus) in NE Greenland.” Journal of Zoology, London 243:381-96.

Dittrich, L. (1987) “Observations on Keeping the Pacific Walrus Odobenus rosmarus divergens at Hanover Zoo.” International Zoo Yearbook 26:163-70.

Eley, T. J., Jr. (1978) “A Possible Case of Adoption in the Pacific Walrus.” Murrelet 59:77-78.

Fay, F. H. (1982) Ecology and Biology of the Pacific Walrus, Odobenus rosmarus divergens Illiger. North American Fauna, no. 74. Washington, D.C.: U.S. Department of the Interior, Fish and Wildlife Service.

———(1960) “Structure and Function of the Pharyngeal Pouches of the Walrus (Odobenus rosmarus L.).” Mammalia 24:361-71.

*Fay, F. H., G. C. Ray, and A. A. Kibal’chich (1984) “Time and Location of Mating and Associated Behavior of the Pacific Walrus, Odobenus rosmarus divergens Illiger.” In F. H. Fay and G. A. Fedoseev, eds., Soviet-American Cooperative Research on Marine Mammals, vol. 1: Pinnipeds, pp. 89-99. NOAA Technical Report NMFS 12. Washington, D.C.: U.S. Department of Commerce.

Fay, F. H., and B. P. Kelly (1980) “Mass Natural Mortality of Walruses (Odobenus rosmarus) at St. Lawrence Island, Bering Sea, Autumn 1978.” Arctic 33:226-45.

*Mathews, R. (1983) “The Summer-Long Bachelor Party on Round Island.” Smithsonian 14:68-75.

Miller, E. H., (1985) “Airborne Acoustic Communication in the Walrus Odobenus rosmarus.” National Geographic Research 1:124-45.

*———(1976) “Walrus Ethology. II. Herd Structure and Activity Budgets of Summering Males.” Canadian Journal of Zoology 54:704-15.

*———(1975) “Walrus Ethology. I. The Social Role of Tusks and Applications of Multidimensional Scaling.” Canadian Journal of Zoology 53:590-613.

*Miller, E. H., and D. J. Boness (1983) “Summer Behavior of Atlantic Walruses Odobenus rosmarus rosmarus (L.) at Coats Island, N.W.T. (Canada).” Zeitschrift für Säugetierkunde 48:298-313.

Nowicki, S. N., I. Stirling, and B. Sjare (1997) “Duration of Stereotyped Underwater Vocal Displays by Male Atlantic Walruses in Relation to Aerobic Dive Limit.” Marine Mammal Science 13:566-75.

Ray, G. C., and W. A. Watkins (1975) “Social Function of Underwater Sounds in the Walrus Odobenus rosmarus.” Rapports et Procès-Verbaux des Réunions, Conseil International pour l’Exploration de la Mer 169:524-26.

*Salter, R. E. (1979) “Observations on Social Behavior of Atlantic Walruses (Odobenus rosmarus [L.]) During Terrestrial Haul-Out.” Canadian Journal of Zoology 58:461-63.

Schevill, W. E., W. A. Watkins, and C. Ray (1966) “Analysis of Underwater Odobenus Calls with Remarks on the Development and Function of the Pharyngeal Pouches.” Zoologica 51:103-6.

*Sjare, B., and I. Stirling (1996) “The Breeding Behavior of Atlantic Walruses, Odobenus rosmarus rosmarus, in the Canadian High Arctic.” Canadian Journal of Zoology 74:897-911.

Stirling, I., W. Calvert, and C. Spencer (1987) “Evidence of Stereotyped Underwater Vocalizations of Male Atlantic Walruses (Odobenus rosmarus rosmarus).” Canadian Journal of Zoology 65:2311-21.

West Indian Manatees are generally solitary and only moderately social; however, they may congregate in loose herds of two to six animals. Some herds are cosexual, while others are “bachelor” groups of younger males.

Behavioral Expression: Male West Indian Manatees of all ages regularly engage in intense homosexual activities. In a typical encounter, two males embrace, rub their genital openings against each other, and then unsheathe or erect their penises and rub them together, often to ejaculation. During a homosexual mating, the two males often tumble to the bottom, thrusting against each other and wallowing in the mud as they clasp each other tightly. A wide variety of positions are used, including embracing in head-to-tail and sideways positions, often with interlocking penises or flipper-penis contact. All of these are distinct from the position used for heterosexual copulation, in which the male typically swims underneath the female on his back and mates with her upside down. Lasting for up to two minutes, homosexual copulations are generally four to eight times longer than heterosexual ones. Before they engage in sexual activity, males often “kiss” each other by touching their muzzles at the surface of the water. In addition, several other types of affectionate and tactile activities are a part of homosexual interactions, including mouthing and caressing of each other’s body, nibbling or nuzzling of the genital region, and riding by one male on the back of the other (a behavior also seen in heterosexual interactions). Sometimes a male emits vocalizations indicating his pleasure during homosexual activity, variously described as high-pitched squeaks, chirp-squeaks, or snort-chirps. If, however, he is not interested in participating, he may emit a squealing sound, slapping his tail as he flees from the other male (just the way females do when trying to escape from unwanted advances of males).

Often several males participate at the same time in homosexual interactions: groups of up to four animals have been seen kissing, embracing each other in an interlocked “hug,” thrusting, and rubbing their penises against one another. These homosexual “orgies” can last for hours as new males arrive to join the group, subgroups form and re-form, and participants leave and return. Homosexual behavior is often part of a social activity known as CAVORTING, in which animals travel and splash about in groups, nuzzling, grabbing, chasing, rubbing, and rolling against one another. Cavorting groups can be mixed-sex or all-male.

Frequency: Homosexuality is common among West Indian Manatees. In addition, males spend on average about 11 percent of their time in cavorting groups.

Orientation: Most male Manatees are probably bisexual, since homosexual behavior is sometimes interspersed with, or develops out of, heterosexual interactions when more than one male is involved. However, much homosexual activity occurs independent of heterosexual activity, and some males may engage primarily in same-sex interactions.

Heterosexual interactions in West Indian Manatees often involve considerable harassment and coercion of females by males. Large, jostling herds containing as many as 17-22 males relentlessly pursue females in heat as well as nonfertilizable females, attempting to copulate with them and often following them for weeks at a time. In her attempts to escape from the males, the female may violently slap her tail, twisting and turning as she dives away, or else tear through the underwater vegetation, even plunging into the mud or stranding herself onshore. Calves whose mothers are being pursued sometimes get lost or are fatally fatigued or injured. Female Manatees generally reproduce only once every three years, and at any given time, only about 30-40 percent of all females are reproducing. Most male Manatees have a distinct seasonal sexual cycle as well, with their testes generally dormant and not producing sperm during the winter months. Females raise their young on their own with no help from the males. However, a mother will occasionally allow another female to nurse her calf or may leave her calf in the company of other mothers and/or their calves while she goes off to feed on her own.

Homosexual activity has also been observed in Dugongs (Dugong dugon), a species of Manatee that inhabits Australasian waters. A pair of captive males, for example, engaged in courtship and sexual behaviors with each other, including rolling, nudging, gentle biting, and splashing, often with erect penises. Although same-sex activity has yet to be documented in wild Dugongs, most observations of mating activity for this species in the wild involve individuals whose sex has not been unequivocally determined.

*asterisked references discuss homosexuality/transgender

*Anderson, P. K. (1997) “Shark Bay Dugongs in Summer. I: Lek Mating.” Behavior 134:433–62.

*Bengtson, J. L. (1981) “Ecology of Manatees (Trichechus manatus) in the St. Johns River, Florida.” Ph.D. thesis, University of Minnesota.

*Hartman, D. S. (1979) Ecology and Behavior of the Manatee (Trichechus manatus) in Florida. American Society of Mammalogists Special Publication no. 5. Pittsburgh: American Society of Mammalogists.

*———(1971) “Behavior and Ecology of the Florida Manatee, Trichechus manatus latirostris (Harlan), at Crystal River, Citrus County.” Ph.D. thesis, Cornell University.

Hernandez, P., J. E. Reynolds, III, H. Marsh, and M. Marmontel (1995) “Age and Seasonality in Spermatogenesis of Florida Manatees.” In T. J. O’Shea, B. B. Ackerman, and H. F. Percival, eds., Population Biology of the Florida Manatee, pp. 84–97. Information and Technology Report 1. Washington, D.C.: U.S. Department of the Interior.

Husar, S. L. (1978) “Trichechus manatus.” Mammalian Species 93:1–5.

*Jones, S. (1967) “The Dugong Dugong dugon (Müller): Its Present Status in the Seas Round India with Observations on Its Behavior in Captivity.” International Zoo Yearbook 7:215–20.

Marmontel, M. (1995) “Age and Reproduction in Female Florida Manatees.” In T. J. O’Shea, B. B. Ackerman, and H. F. Percival, eds., Population Biology of the Florida Manatee, pp. 98–119. Information and Technology Report 1. Washington, D.C.: U.S. Department of the Interior.

Moore, J. C. (1956) “Observations of Manatees in Aggregations.” American Museum Novitates 1811:1–24.

*Nair, R. V., R. S. Lal Mohan, and K. Satyanarayana Rao (1975) The Dugong Dugong dugon. ICAR Bulletin of the Central Marine Fisheries Research Institute no. 26. Cochin, India: Central Marine Fisheries Research Institute.

Preen, A. (1989) “Observations of Mating Bevavior in Dugongs (Dugong dugon).” Marine Mammal Science 5:382-87.

*Rathbun, G. B., J. P. Reid, R. K. Bonde, and J. A. Powell (1995) “Reproduction in Free-ranging Florida Manatees.” In T. J. O’Shea, B. B. Ackerman, and H. F. Percival, eds., Population Biology of the Florida Manatee, pp. 135-56. Information and Technology Report 1. Washington, D.C.: U.S. Department of the Interior.

Reynolds, J. E., III. (1981) “Aspects of the Social Behavior and Herd Structure of a Semi-Isolated Colony of West Indian Manatees, Trichechus manatus.” Mammalia 45:431-51.

———(1979) “The Semisocial Manatee.” Natural History 88(2):44-53.

Reynolds, J. E., III., and D. K. Odell (1991) Manatees and Dugongs. New York: Facts on File.

*Ronald, K., L. J. Selley, and E. C. Amoroso (1978) Biological Synopsis of the Manatee. Ottawa: International Development Research Center.

DEER

During most of the year, White-tailed and Mule Deer live in sex-segregated groups: females form groups with other does and their offspring, while males (bucks) live in “bachelor” groups or on their own. During the rutting season, males form short-lived, consecutive “tending bonds” with multiple females—a form of polygamy or “serial monogamy.” Larger cosexual groups may also form during the winter.

Behavioral Expression: Adult male White-tailed Deer sometimes mount each other, as do yearling males (especially during the nonbreeding season); occasionally a younger male mounts an older one during this activity. Homosexual mounts (like heterosexual ones) are usually preceded by one male nuzzling the other’s rear end, and sometimes one male mounts another twice in a row; occasionally the mounting buck has an erection. The mount may be briefer than a male-female copulation, but the same duration as heterosexual nonreproductive mounts (5-15 seconds, as opposed to 15-20 seconds). Yearling Mule Deer occasionally mount each other during SPARRING MATCHES—ritualized, nonviolent contests in which the bucks lock horns. During this activity one male might assume a stiffened posture, similar to a female’s before copulation. The other male—sometimes younger or smaller than the first—then mounts him, after first licking and smelling the special scent-producing glands on his hind legs. Female Mule Deer also sometimes mount each other when in heat; in addition, some does court other females using a chasing sequence known as RUSH COURTSHIP. In this behavior (which also occurs in heterosexual contexts), they race toward another female, stopping abruptly and sometimes pawing the ground, pacing, leaping into the air while twisting their body, or running in circles or figure eights; this causes the other doe to become excited and aroused. Adult male White-tailed Deer frequently develop “companionships” or bonds with one (or occasionally two) other adult males in their buck groups; male companions are generally not related to each other. These strong attachments constitute the stable “core” of each buck group, and although male companions typically separate during the breeding season, they usually resume their bonds once mating is over.

An extraordinary form of transgendered deer occurs in some populations of White-tails. These animals, which are genetically male but actually combine characteristics of both males and females, are sometimes called VELVET-HORNS because their antlers are permanently covered with the special “velvet” skin that in most males is shed after the antlers have grown. Their antlers are usually only spikes (without the extensive branching of other males’ antlers) and they slope backward and sometimes have enlarged bases. Physically, velvet-horns often have body proportions and facial features more typical of does, while their testes are small and undeveloped (and in fact the animals are infertile). A similar type of transgender is found among Mule Deer, where the animals are known as CACTUS BUCKS owing to the distinctive shape of their antlers (which sometimes also have elaborate spikes, prongs, and asymmetrical growths). Velvet-horns usually form their own social groups of three to seven animals and live separately from both does and nontransgendered males. In fact, they are often harassed and attacked by other deer. Nontransgendered White-tails (both does and bucks of all ages, even fawns) threaten velvet-horns who try to approach them—forcing them to remain no less than ten feet away—while bucks may actively charge velvet-horns to drive them away. When threatened, velvet-horns flee without giving the standard alarm signals of other deer (stamping their feet, snorting or whistling, and raising their tails). Sometimes, groups of up to six bucks “gang up” on a velvet-horn, chasing and even violently attacking it by gashing its rump with their antlers. As a result, velvet-horns are extremely wary around other deer, venturing near feeding areas cautiously and always remaining in groups on the periphery, or else refusing to approach at all when other deer are present. Interestingly, velvet-horns are almost always in superior physical condition compared to nontransgendered males, precisely because they do not breed. The rutting season is extremely taxing on breeding bucks, who rarely eat and may lose up to a quarter of their body weight. In contrast, velvet-horns consistently have excellent body fat deposits and are in prime shape.

Two types of gender-mixing females also occur among White-tailed and Mule Deer, both bearing antlers (females in these species do not usually have antlers). In one type, the antlers are similar to those of velvet-horns: they are permanently covered in velvet, are never shed, and are either spikes or asymmetrically branching. Unlike velvet-horns, such females are usually fertile, mating heterosexually and becoming mothers. The other type is a more complete form of intersexuality: the antlers are hard and polished, more closely resemble those of males in their branching structure, and may even be shed seasonally. These individuals usually combine both male and female sexual traits, such as having the genitalia and/or reproductive organs of both sexes, or partial organs of each sex, or chromosomes of one sex combined with the genitalia of the other.

Frequency: Homosexual mounting probably occurs only occasionally among White-tailed and Mule Deer; however, in one study of White-tails, two out of ten observed mountings were same-sex. Up to 10 percent of males are velvet-horns in some areas, although their incidence fluctuates. In some years they may constitute as many as 40-80 percent of all males in a given population. One study of a White-tailed Deer population over 14 years found that 1-2 percent of the females had antlers; overall, approximately 1 in every 1,000-1,100 does is antlered.

Orientation: Most Deer that participate in same-sex mounting probably also engage in heterosexual courtship and copulation. Gender-mixing Deer that are fertile (almost always genetically female) are usually heterosexual (i.e., they mate with genetic males), while nonfertile transgendered Deer (e.g., velvet-horns) are probably asexual or associate only with other transgendered Deer.

Deer participate in a variety of nonprocreative sexual behaviors besides homosexuality. White-tails sometimes engage in heterosexual mountings outside of the mating season, which are nonreproductive for two reasons. They often do not involve penetration, and bucks have a seasonal sexual cycle, so that during the spring and summer their testes are small and produce little, if any, sperm. Mating episodes among Mule Deer during the breeding season often involve the male performing extensive non-insertive sexual activity prior to actual copulation: in this activity he mounts the female with his penis erect (unsheathed) but without penetration. These mounts may be fairly lengthy—up to 15 seconds—and frequent (anywhere from 5 to more than 40 in one session). Bucks of both species sometimes masturbate in a unique fashion: the penis is first unsheathed and licked, then stimulated by moving it back and forth (via pelvic rotations and thrusts) in its sheath or against the belly until orgasm is reached. Because their antlers are actually sensitive—even erotic—organs (as in several other species of Deer), buck Mule Deer also sometimes sexually stimulate themselves by rubbing their antlers on vegetation. Incestuous activity—including fawns mounting their mothers—also occurs in these species.

As mentioned above, sex segregation is a notable feature of White-tailed Deer society. This pattern usually begins during the fawning period, when does become aggressive toward adult males and may even kick and chase them away. When their male fawns become yearlings, females also drive them away in the same violent fashion. In addition to nonbreeding transgendered animals, other nonreproducing individuals occur. White-tail bucks often do not mate until they are three to five years old; because of the physical stresses of reproduction, bucks that delay breeding may actually grow larger than those that reproduce earlier. When breeding does occur, females of both species sometimes terminate their pregnancies by aborting the fetus or reabsorbing the embryo. This probably occurs in 1-10 percent of Mule Deer pregnancies, but is more likely to happen when unfavorable climate and forage would make it difficult for mothers to feed and care for their young.

*asterisked references discuss homosexuality/transgender

*Anderson, A. E. (1981) “Morphological and Physiological Characteristics.” In O. C. Wallmo, ed, Mule and Black-tailed Deer of North America, pp. 27-97. Lincoln and London: University of Nebraska Press.

*Baber, D. W. (1987) “Gross Antler Anomaly in a California Mule Deer: The ‘Cactus’ Buck.” Southwestern Naturalist 32:404-6.

Brown, B. A. (1974) “Social Organization in Male Groups of White-tailed Deer.” In V. Geist and F. Walther, eds., The Behavior of Ungulates and Its Relation to Management, vol. 1, pp. 436-46. IUCN Publication no. 24. Morges, Switzerland: International Union for Conservation of Nature and Natural Resources.

*Cowan, I. McT. (1946) “Antlered Doe Mule Deer.” Canadian Field-Naturalist 60: 11-12.

*Crispens, C. G., Jr., and J. K. Doutt (1973) “Sex Chromatin in Antlered Female Deer.” Journal of Wildlife Management 37:422-23.

*Donaldson, J. C., and J. K. Doutt (1965) “Antlers in Female White-tailed Deer: A 4-Year Study.” Journal of Wildlife Management 29:699-705.

*Doutt, J. K., and J. C. Donaldson (1959) “An Antlered Doe With Possible Masculinizing Tumor.” Journal of Mammalogy 40:230-36.

*Geist, V. (1981) “Behavior: Adaptive Strategies in Mule Deer.” In O. C. Wallmo, ed., Mule and Black-tailed Deer of North America, pp. 157-223. Lincoln and London: University of Nebraska Press.

*Halford, D. K., W. J. Arthur III, and A. W. Alldredge (1987) “Observations of Captive Rocky Mountain Mule Deer Behavior.” Great Basin Naturalist 47:105-9.

*Hesselton, W. T., and R. M. Hesselton (1982) “White-tailed Deer.” In J. A. Chapman and G. A. Feldhamer, eds., Wild Mammals of North America: Biology, Management, and Economics, pp. 878-901. Baltimore and London: Johns Hopkins University Press.

*Hirth, D. H. (1977) “Social Behavior of White-Tailed Deer in Relation to Habitat.” Wildlife Monographs 53:1-55.

Jacobson, H. A. (1994) “Reproduction.” In D. Gerlach, S. Atwater, and J. Schnell, eds., Deer, pp. 98-108. Mechanicsburg, Pa.: Stackpole Books.

Marchinton, R. L., and D. H. Hirth (1984) “Behavior.” in L. K. Halls, ed., White-tailed Deer: Ecology and Management, pp. 129-68. Harrisburg, Pa.: Stackpole Books; Washington, DC: Wildlife Management Institute.

Marchinton, R. L. and W. G. Moore (1971) “Auto-erotic Behavior in Male White-tailed Deer.” Journal of Mammalogy 52:616-17.

*Rue, L. L., III (1989) The Deer of North America. 2nd ed. Danbury, Conn.: Outdoor Life Books.

Sadleir, R. M. F. S. (1987) “Reproduction of Female Cervids.” In C. M. Wemer, ed., Biology and Management of the Cervidae, pp. 123-44. Washington, D.C.: Smithsonian Institution Press.

Salwasser, H., S. A. Holl, and G. A. Ashcraft (1978) “Fawn Production and Survivial in the North Kings River Deer Herd.” California Fish and Game 64:38-52.

*Taylor, D. O. N., J. W. Thomas, and R. G. Marburger (1964) “Abnormal Antler Growth Associated with Hypogonadism in White-tailed Deer of Texas.” American Journal of Veterinary Research 25:179-85.

*Thomas, J. W., R. M. Robinson, and R. G. Marburger (1970) Studies in Hypogonadism in White-tailed Deer of the Central Mineral Region of Texas. Texas Parks and Wildlife Department Technical Series no. 5. Austin: Texas Parks and Wildlife Department.

*———(1965) “Social Behavior in a White-tailed Deer Herd Containing Hypogonadal Males.” Journal of Mammalogy 46:314-27.

*———(1964) “Hypogonadism in White-tailed Deer in the Central Mineral Region of Texas.” In J. B. Trefethen, ed., Transactions of the North American Wildlife and Natural Resources Conference 29:225-36. Washington, D.C.: Wildlife Management Institute.

*Wishart, W. D. (1985) “Frequency of Antlered White-tailed Does in Camp Wainright, Alberta.” Journal of Mammalogy 35:486-88.

*Wislocki, G. B. (1956) “Further Notes on Antlers in Female Deer of the Genus Odocoileus.” Journal of Mammalogy 37:231-35.

*———(1954) “Antlers in Female Deer, With a Report on Three Cases in Odocoileus.” Journal of Mammalogy 35:486-95.

*Wong, B, and K. L. Parker (1988)“Estrus in Black-tailed Deer.” Journal of Mammalogy 69:168-71.

Male Wapiti/Red Deer live for nine to ten months of the year in bachelor groups, while females (cows or hinds) associate with each other and their offspring in matriarchal groups. During the rut, which lasts for one to two months, males herd females and mate polygamously with them. Barasingha generally live in groups of 3-13 animals, although toward the end of the rutting season aggregations of up to 70 Deer may form. During most of the year Barasingha herds are sex-segregated.

Behavioral Expression: In both of these Deer species, homosexual mounting occurs outside of the breeding season—in females among Barasingha, and in both sexes among Wapiti and Red Deer (Wapiti or Elk is the name for this species in North America, Red Deer is the European name). In addition, Red Deer hinds sometimes mount one another when they are in heat during the breeding season. Female homosexual mounting in Wapiti generally takes place in the cow groups. Usually the two animals engaging in same-sex activity are fully grown adults, but in male Wapiti homosexual mounting may occur between adult bulls and spikehorns (yearlings whose antlers are spikes, having yet to develop prongs). Red Deer yearlings also participate in same-sex activity, including occasional incestuous homosexual mountings by females of their mothers. Homosexual mounting is done in the same position as heterosexual mating, with one animal behind the other; Red Deer stags have been observed with a full erection when mounting another male. In Wapiti and female Red Deer, same-sex (and opposite-sex) mounting may also be preceded by CHIN-RESTING, in which one animal rests its chin on the rump of the other, signaling his or her intention to mount. About a third of all Red Deer females participate in homosexual mounting as both mounter and mountee, while another third only participate as mounters, and another third only as mountees. Reciprocal mounting—in which two animals take turns mounting each other—sometimes occurs in male Wapiti. A type of same-sex, “platonic” pair-bonding is also found in this species. Both males and females may form “companionships” with an animal of the same sex; female companions are usually of the same age, while male companions may be two adult bulls, or an adult male with a younger male. Occasionally bulls will try to separate female companions during the breeding season. Their bond is strong, however, and the females travel great distances to rejoin each other, calling toward their companion until they are reunited.

Among Red Deer, gender-mixing individuals with various antler configurations are occasionally found. In this species, the vast majority of males have antlers; however, some stags, known as HUMMELS, physically resemble females in that they do not have this secondary sexual characteristic. Interestingly, hummels are in many ways more successful than antlered stags. Many become “master stags,” that is, the highest ranking males, because they are generally in better physical condition, more resourceful, better fighters (in spite of not having antlers), and more successful at mating with females than antlered males. In addition, a few males are PERUKES, that is, their antlers are spikes and permanently covered in velvet. Such males are generally nonreproductive, having undeveloped testes. Antlered females also sometimes occur.

Frequency: Same-sex mounting occurs occasionally among Wapiti; in Barasingha, approximately 2-3 percent of sexual activity is between females. Homosexual mounting makes up about a third of all mounting behavior outside the breeding season in Red Deer, with the majority of this activity (64 percent) taking place between females.

Orientation: In Red Deer, about 70 percent of all females engage in some homosexual activity outside the rutting season; of these, about 30 percent participate exclusively in homosexuality, while the remainder are bisexual. The proportion of homosexual activity in bisexual females ranges from 6 percent to 80 percent, with the average being about 48 percent same-sex mounting per individual. Life histories of individual Wapiti and Barasingha that participate in homosexual mounts have not been compiled, so it is not known whether they also engage in heterosexual behavior.

Significant portions of the Wapiti and Red Deer population do not participate in reproduction. Only about a third of adult male Wapiti and half of adult male Red Deer mate with females each year. In fact, some Red Deer males (and a few females) are lifetime nonbreeders, never fathering offspring; others may have a postreproductive period in their old age. Moreover, about 30 percent of females, on average, are nonreproductive each season; individuals that do not breed generally have a lower mortality rate than breeders. As described above, Deer society is largely sex-segregated: males and females live mostly separate from each other except for one month out of the year (during the breeding season). Nevertheless, some heterosexual activity does take place outside of the rutting season: younger male Wapiti—often those that did not breed the previous season—may try to court and mount females, and heterosexual mounting also occurs outside the rut in Red Deer. Interestingly, some female Wapiti come into heat outside of the breeding season, but they are usually ignored by most adult males.

Even during the breeding season, heterosexual relations are sometimes strained: female Wapiti often refuse to be mounted by adult males, and they bite or kick yearling males that try to mate with them. On the other hand, a variety of nonprocreative sexual behaviors also make up the heterosexual repertoire: male Wapiti and Red Deer may lick and nuzzle the female’s genitals, while REVERSE mounts (in which the female mounts the male) make up more than a quarter of all heterosexual activity outside the breeding season in Red Deer (they also occur in Wapiti). Both Red Deer and Wapiti males also masturbate, using a fairly unusual method: antlers in these species are actually erotic zones, and males derive sexual stimulation by rubbing them against vegetation. Red Deer stags have regularly been observed developing an erection and ejaculating from this activity. Sexual behavior by calves—including adult-calf interactions—also occurs in these species. Wapiti/Red Deer calves sometimes mount adults (including their mothers, in Red Deer), while female Red Deer occasionally mount calves. More than half of all mounting by yearling Red Deer is incestuous, with the younger animal mounting its mother. Finally, Wapiti females have developed a communal parenting or “day-care” system of CALF POOLS or CRÈCHES. These nursery groups, containing up to 50 or more calves, form in late summer to early fall, with one or two females watching over the youngsters while the other mothers go off on their own.

In Pere David’s Deer (Elaphurus davidianus) stags sometimes mount each other, with younger males typically mounting older ones. Male Reeve’s Muntjacs (Muntiacus reevesi), a small Chinese Deer, sometimes court other males. Transgendered peruke stags occasionally occur in other species such as Sika Deer (Cervus nippon)—where they may have a female coat color—Roe Deer (Capreolus capreolus), and Fallow Deer (Dama dama). In addition, intersexual individuals combining the genitals or reproductive organs of both sexes also occur in these species, as do Indian Muntjacs (Muntiacus muntjak) with a combined male-female chromosomal pattern (XXY).

*asterisked references discuss homosexuality/transgender

Altmann, M. (1952) “Social Behavior of Elk, Cervus canadensis nelsoni, in Jackson Hole Area of Wyoming.” Behavior 4:116-43.

*Barrette, C. (1977) “The Social Behavior of Captive Muntjacs Muntiacus reevesi (Ogilby 1839).” Zeitschrift für Tierpsychologie 43:188-213.

*Chapman, D. I., N. G. Chapman, M. T. Horwood, and E. H. Masters (1984) “Observations on Hypogonadism in a Perruque Sika Deer (Cervus nippon).” Journal of Zoology, London 204:579-84.

Clutton-Brock, T. H., F. E. Guiness, and S. D. Albon (1983) “The Costs of Reproduction to Red Deer Hinds.” Journal of Animal Ecology 52:367-83.

———(1982) Red Deer: Behavior and Ecology of Two Sexes. Chicago: University of Chicago Press.

*Darling, E E (1937) A Herd of Red Deer. London: Oxford University Press.

*Donaldson, J. C., and J. K. Doutt (1965) “Antlers in Female White-tailed Deer: A 4-Year Study.” Journal of Wildlife Management 29:699-705.

Franklin, W. L., and J. W. Lieb (1979) “The Social Organization of a Sedentary Population of North American Elk: A Model for Understanding Other Populations.” In M. S. Boyce and L. D. Hayden-Wing, eds., North American Elk: Ecology, Behavior, and Management, pp. 185-98. Laramie: University of Wyoming.

Graf, W. (1955) The Roosevelt Elk. Port Angeles, Wash.: Port Angeles Evening News.

*Guiness, E, G. A. Lincoln, and R.V. Short (1971) “The Reproductive Cycle of the Female Red Deer, Cervus elaphus L.” Journal of Reproduction and Fertility 27:427-38.

*Hall, M. J. (1983) “Social Organization in an Enclosed Group of Red Deer (Cervus elaphus L.) on Rhum. II. Social Grooming, Mounting Behavior, Spatial Organization, and Their Relationships to Dominance Rank.” Zeitschrift für Tierpsychologie 61:273-92.

*Harper, J. A., J. H. Harn, W. W. Bentley, and C. F. Yocom (1967) “The Status and Ecology of the Roosevelt Elk in California.” Wildlife Monographs 16: 1-49.

*Lieb, J. W. (1973) “Social Behavior in Roosevelt Elk Cow Groups.” Master’s thesis, Humboldt State University.

*Lincoln, G. A., R. W. Youngson, and R. V. Short (1970) “The Social and Sexual Behavior of the Red Deer Stag.” Journal of Reproduction and Fertility suppl. 11:71-103.

Martin, C. (1977) “Status and Ecology of the Barasingha (Cervus duvauceli branderi) in Kanha National Park (India).” Journal of the Bombay Natural History Society 74:60-132.

Morrison, J. A. (1960) “Characteristics of Estrus in Captive Elk.” Behavior 16:84-92.

Prothero, W. L., J. J. Spillett, and D. E Balph (1979) “Rutting Behavior of Yearling and Mature Bull Elk: Some Implications for Open Bull Hunting.” In M. S. Boyce and L. D. Hayden-Wing eds., North American Elk: Ecology, Behavior, and Management, pp. 160-65. Laramie: University of Wyoming.

*Schaller, G. B. (1967) The Deer and the Tiger. Chicago: University of Chicago Press.

*Schaller, G. B., and A. Hamer (1978) “Rutting Behavior of Père David’s Deer, Elaphurus davidianus.” Zoologische Garten 48:1-15.

*Wurster-Hill, D. H., K. Benirschke, and D. I. Chapman (1983) “Abnormalities of the X Chromosome in Mammals.” In A. A. Sandberg, ed., Cytogenetics of the Mammalian X Chromosome, Part B, pp. 283–300. New York: Alan R. Liss.

Caribou are highly gregarious, sometimes forming herds of tens or even hundreds of thousands of animals (although most groups contain 40–400 animals). They typically associate in all-male, mother-calf, and juvenile/adolescent bands. Moose, on the other hand, are more solitary, although they form aggregations of up to several dozen animals during the fall rutting period. Groups of bulls and cosexual herds may also coalesce after the mating season. In both species, animals mate with multiple partners rather than forming long-term heterosexual bonds, and males do not participate in raising their young (i.e., they have a polygamous mating system).

Behavioral Expression: Caribou and Moose occasionally participate in a variety of same-sex courtship and sexual activities. Male Moose, for example, sometimes direct courtship behaviors toward other males, including sniffing the anal and genital region, and approaching another bull while making the characteristic rutting sound, the CROAK (a grunting call that combines a deep, resonant syllable with a popping or suction noise). Younger male Caribou may also court other males by making a similar sound, sometimes known as SLURPING or VACUUM LICKING, in which the animal flicks or smacks his tongue against the upper palate while approaching the other male with his head outstretched. Female Caribou sometimes mount each other, as do younger males, while yearling male Moose have been observed trying to mount adult bulls. In addition, bull Moose sometimes associate with younger male companions—known as SATELLITES—that travel together in pairs or small groups, usually outside the breeding season. Another homosexual activity among males in both Moose and Caribou is antler rubbing. In these two species (as in several other types of Deer), antlers are highly sensitive organs and genuine erotic zones, and males may become sexually aroused when they rub their antlers together. Among Moose, this is done rather gently as a sort of “play-fighting” (the antlers may still have their velvet covering), while Caribou males rattle their antlers against each other when they are free of velvet.

Several types of gender-mixing occasionally occur in Moose, often involving unusual antler configurations. Intersexed males lacking a scrotum or testes sometimes develop what are known as VELERICORN antlers, which are covered in velvet and festooned with various ridges and knobs; such antlers are permanent, unlike regular antlers, which are shed and regrown each season. Other males—sometimes known as PERUKES—have elaborate, misshapen antlers covered with baroque nodule-like growths. Occasionally, females develop antlers, which may be single; spiked (without branches); covered in velvet; or lacking the flat, palmated structure typical of male Moose antlers. Caribou are the only deer in which females regularly sport antlers: depending on the population, anywhere from 8–95 percent of females may be antlered.

Frequency: Homosexual activity occurs only sporadically in Moose and Caribou. About a quarter of all male Moose associate together in pairs during at least part of the year.

Orientation: Adult animals that participate in homosexual activities in these two species are, in all likelihood, predominantly heterosexual, albeit with some bisexual capability. Some younger animals—especially among male Moose—may tend toward a less heterosexually oriented bisexuality, since many do not fully participate in heterosexual mating.

In both Moose and Caribou, many animals do not procreate. Caribou males are physiologically capable of breeding when they are a year old, yet most do not mate until they are at least four years old since they cannot successfully compete with the older bucks; a similar pattern is found in Moose. Among Caribou, females without calves may associate with a breeding female as an “assistant mother,” and some even try to “kidnap” or lure a calf away from its biological mother. During severe food shortages, pregnant Caribou females may terminate the breeding process by reabsorbing their embryos, since they would not be able to successfully raise their calves under such conditions. Approximately 8 percent of the male Caribou population consists of older (10+ years), postreproductive males that do not participate in breeding. However, many stags never reach this age, since the life expectancy of males is considerably shorter than that of females, at least in part because of the stresses associated with breeding. In Moose, breeding is also a taxing activity for bulls, who fast completely during the rutting period. Mating can also be a traumatic activity for females: because males in these two species are considerably larger, females often suffer injuries from copulation, sometimes literally collapsing under the weight of a male mounting them. As a result, female Caribou often strongly resist mating attempts and struggle to escape (less than two-thirds of matings are completed), while males may strike them with their antlers to make them submit to mounting. Females, in turn, may use their own antlers to fight back. Female Moose often strike males with their front hooves during the rutting season as well, and are capable of inflicting serious injury. In both species, there is significant segregation of the sexes outside of the breeding season: in Moose, for example, only 10–20 percent of winter groups are cosexual.

Moose and Caribou also participate in a variety of nonreproductive sexual behaviors. Males of both species sometimes try to mount calves, and female Caribou sometimes REVERSE mount males. Heterosexual interactions often involve oral-genital contact—male Moose and Caribou lick the female’s vulva, while female Caribou sometimes lick the male’s penis. About 45 percent of heterosexual mounts in Moose do not involve penetration or ejaculation, and males sometimes mount females up to 14 times in a sequence. In addition, both male Moose and Caribou “masturbate” by rubbing their antlers against vegetation, which often results in sexual stimulation (including erection of the penis and possibly ejaculation).

*asterisked references discuss homosexuality/transgender

Altmann, M. (1959) “Group Dynamics in Wyoming Moose During the Rutting Season.” Journal of Mammalogy 40:420–24.

*Bergerud, A. T. (1974) “Rutting Behavior of Newfoundland Caribou.” In V. Geist and F. Walther, eds., The Behavior of Ungulates and Its Relation to Management, vol. 1, pp. 395–435. IUCN Publication no. 24. Morges, Switzerland: International Union for Conservation of Nature and Natural Resources.

*Bubenik, A. B., G. A. Bubenik, and D. G. Larsen (1990) “Velericorn Antlers on a Mature Male Moose (Alces a. gigas).” Alces 26:115–28.

Bubenik, A. B., and H. R. Timmerman (1982) “Spermatogenesis of the Taiga-Moose—a Pilot Study.” Alces 18:54–93.

*Denniston, R. H., II (1956) “Ecology, Behavior, and Population Dynamics of the Wyoming or Rocky Mountain Moose, Alces alces shirasi.” Zoologica 41: 105–18.

de Vos, A. (1958) “Summer Observations on Moose Behavior in Ontario.” Journal of Mammalogy 39:128–39.

*Dodds, D. G. (1958) “Observations of Pre-Rutting Behavior in Newfoundland Moose.” Journal of Mammalogy 39:412–16.

*Geist, V (1963) “On the Behavior of the North American Moose (Alces alces andersoni Peterson 1950), in British Columbia.” Behavior 20:377–416.

Houston, D. B. (1974) “Aspects of the Social Organization of Moose.” In V. Geist and F. Walther, eds., The Behavior of Ungulates and Its Relation to Management, vol. 2, pp. 690–96. IUCN Publication no. 24. Morges, Switzerland: International Union for Conservation of Nature and Natural Resources.

Kojola, I. (1991) “Influence of Age on the Reproductive Effort of Male Reindeer.” Journal of Mammalogy 72:208–10.

*Lent, P. C. (1974) “A Review of Rutting Behavior in Moose.” Naturaliste canadien 101:307–23.

———(1966) “Calving and Related Social Behavior in the Barren-Ground Caribou.” Zeitschrift für Tierpsychologie 23:701–56.

Miquelle, D. G., J. M. Peek, and V. Van Ballenberghe (1992) “Sexual Segregation in Alaskan Moose.” Widlife Monographs 122:1–57.

*Murie, O. J. (1928) “Abnormal Growth of Moose Antlers.” Journal of Mammalogy 9:65.

*Pruitt, W. O., Jr. (1966) “The Function of the Brow-Tine in Caribou Antlers.” Arctic 19:111-13.

———(1960) “Behavior of the Barren-Ground Caribou.” Biological Papers of the University of Alaska 3:1–44.

*Reimers, E. (1993) “Antlerless Females Among Reindeer and Caribou.” Canadian Journal of Zoology 71:1319–25.

Skogland, T. (1989) Comparative Social Organization of Wild Reindeer in Relation to Food, Mates, and Predator Avoidance. Advances in Ethology no. 29. Berlin and Hamburg: Paul Parey Scientific Publishers.

Van Ballenberghe, V, and D. G. Miquelle (1993) “Mating in Moose: Timing, Behavior, and Male Access Patterns.” Canadian Journal of Zoology 71:1687–90.

*Wishart, W. D. (1990) “Velvet-Antlered Female Moose (Alces alces).” Alces 26:64–65.

GIRAFFES, ANTELOPES, AND GAZELLES

Female Giraffes tend to congregate in groups of up to 15 individuals, including their calves and perhaps a few younger males. Males generally associate in all-male “bachelor” groups, but tend to become solitary as they get older. The mating system is polygamous: mostly a few older males mate with more than one female, but take no part in raising their offspring.

Behavioral Expression: Male Giraffes have a unique “courtship” or affectionate activity called NECKING, which is often associated with homosexual mounting. When necking, two males stand side by side, usually facing in opposite directions, while they gently rub their necks on each other’s body, head, neck, loins, and thighs, sometimes for as long as an hour. Necking sessions are usually initiated with one male assuming a formal posture with his neck held rigid and upright. One male may also affectionately lick the other’s back or sniff his genitals during necking. Necking Giraffes also sometimes swing their necks at each other in what has been described as a “stately dance” or a form of play-fighting (although they rarely hit, and virtually never injure, each other). Necking usually leads to sexual arousal: one or both males develop erections, and occasionally one might exhibit a curling of the lip similar to the FLEHMEN response seen in heterosexual courtships (associated with sexual arousal and testing sexual “readiness”). Sometimes after necking for 15 minutes or so, one male suddenly stops and “freezes” with his neck stretched forward, which is thought to indicate intense sexual excitement approaching orgasm. Males also commonly mount each other with erect penises during or following bouts of necking and probably reach orgasm (sometimes liquid—presumably semen—can be seen streaming from their penises). At times, groups of four or five males will gather to neck and mount each other, and males may mount several individuals in quick succession or the same male as many as three times in a row. Females also occasionally mount each other, but they do not participate in necking.

Frequency: Homosexual activity is common in Giraffes and in many cases is actually more frequent than heterosexual behavior (which may be quite rare): in one study area, mountings between males accounted for 94 percent of all observed sexual activity. Anywhere from a third to three-quarters of all courtship sessions are homosexual (i.e. they involve necking between males), and at any given time, about 5 percent of all males are participating in necking. Among females, less than 1 percent of interactions involving body contact consist of homosexual mounting.

Orientation: Homosexual activity is characteristic of younger adult males, who may constitute more than 80 percent of the male population. As they get older, males participate less in homosexual courtship and mounting and more in heterosexual activity. Among younger males, it is likely that all of their mounting behavior is homosexual, although a small percentage also court (but do not mount) females. Males participating in homosexual mounting and necking frequently disregard any females present in the herd, perhaps indicating a “preference” for same-sex activity.

Only a relatively small percentage of adult Giraffes breed: in some populations, less than a quarter of the females reproduce in any year, while usually only one or two males actually mate with females. A number of factors contribute to this infrequency of breeding: pregnancies last 15 months, and there is a minimum of 20 months between calves. Males are unable to compete successfully for matings until they are at least eight years old, even though they mature sexually at under four years. And as mentioned above, actual copulations can be remarkably rare—in one population, only a single heterosexual mating was observed during more than 3,200 hours of detailed observation over an entire year. In some areas, it also appears that a small class of old, postreproductive males are generally solitary and do not court or mate with females. Giraffes engage in a few forms of nonprocreative heterosexual activity as well: younger females in heat occasionally mount male calves, while calves sometimes mount their mothers. As in most polygamous animals, males do not participate in calf-raising. Females, however, often leave their young in nursery groups or CALVING POOLS containing as many as nine other calves, attended by one or more of the other mothers. This “day-care” arrangement allows a female to feed on her own without having to constantly look after her calf.

*asterisked references discuss homosexualityltransgender

*Coe, M. J. (1967) “‘Necking’ Behavior in the Giraffe.” Journal of Zoology, London 151:313–21.

*Dagg, A. I., and J. B. Foster (1976) The Giraffe: Its Biology, Behavior, and Ecology. New York: Van Nostrand Reinhold.

*Innis, A. C. (1958) “The Behavior of the Giraffe, Giraffa camelopardalis, in the Eastern Transvaal.” Proceedings of the Zoological Society of London 131:245–78.

Langman, V. A. (1977) “Cow-Calf Relationships in Giraffe (Giraffa camelopardalis giraffa).” Zeitschrift für Tierpsychologie 43:264–86.

*Leuthold, B. M. (1979) “Social Organization and Behavior of Giraffe in Tsavo East National Park.” African Journal of Ecology 17:19–34.

*Pratt, D. M., and V. H. Anderson (1985) “Giraffe Social Behavior.” Journal of Natural History 19:771–81.

———(1982) “Population, Distribution, and Behavior of Giraffe in the Arusha National Park, Tanzania.” Journal of Natural History 16:481–89.

———(1979) “Giraffe Cow-Calf Relationships and Social Development of the Calf in the Serengeti.” Zeitschrift für Tierpsychologie 51:233–51.

*Spinage, C. A. (1968) The Book of the Giraffe. London: Collins.

Pronghorn society is characterized by a distinction between territorial males, who establish territories and mate with females, and nonterritorial males, who live primarily in bachelor herds of seven to ten individuals throughout the spring and into early fall. Females associate in groups of up to two dozen individuals, often accompanied by a territorial male. After the breeding season—during which males copulate with multiple partners and do not assist in parenting—most Pronghorns join large mixed-sex herds for the winter.

Behavioral Expression: Male Pronghorns court and mount each other in their bachelor herds from April to October, using many of the same behavior patterns found in heterosexual courtship and mating. As a prelude to sexual behavior, one male follows another, sometimes sniffing his anal region. The courting male might then touch his chest to the other male’s rump, a signal that he wants to mount. Usually this leads to a full mount, in which the courting male rises on his hind legs and, with erect penis, slides up onto the other male from behind. Sometimes a whole string or “chain” of courting males forms as each follows and tries to mount the male in front of him. Males of all age groups participate in homosexual courtship and mounting, although adult males usually direct their attentions to adolescent males. Mounting between males sometimes occurs during sparring or play-fighting as well. Female Pronghorns also rump-sniff and mount each other when they are in heat, though less frequently than males.

Male Pronghorns shed their horns after the breeding season and some researchers have suggested that this allows them to “pass” as females in mixed-sex herds during the winter. Since males are usually physically exhausted after the rut, they make easier targets for predators than females: by engaging in a form of female mimicry or transvestism, they may avoid being singled out.

Frequency: Overall, about 7 percent of all courtship/sexual behavior is between animals of the same sex, and about 10 percent of all mounts are homosexual (roughly two-thirds of these are between males). Among animals of the same sex, approximately 3–4 percent of their interactions involve some sort of sexual behavior.

Orientation: Anywhere from two-thirds to three-quarters of the male population does not participate in breeding; many of these animals are exclusively homosexual. Two-year-old males, for example, never mount females, yet bachelors participate in nearly a third of all homosexual mounts. At the other end of the scale, territorial males are exclusively heterosexual. In between, various forms of bisexuality occur. About 7 percent of adult bachelor males are able to mate with females, yet they also account for 18 percent of homosexual interactions. Some males transfer from the bachelor herds to territorial status, thereby participating in sequential bisexuality over the course of their lives. Many males, however, never become territorial, and though they may try to court females, most of their sexual behavior will continue to be homosexual for the majority—if not the totality—of their lives.

As described above, the majority of the male population is not involved in procreation, living as they do in bachelor herds or as loners, and Pronghorn social life is characterized by sex segregation for six to seven months of the year. Some bachelors, however, do try to court females; although their advances are consistently rebuffed, the males often persist and may harass the females relentlessly by chasing them, horning and roaring at them, and sometimes even knocking them down during a chase. Reproduction in the Pronghorn is also characterized by aggression within the womb: procreation routinely involves embryos killing each other. As many as seven embryos may initially be present in the female’s uterus, but only two of these will survive. The remainder are killed by the other developing fetuses, which grow long projections out of their fetal membranes that fatally puncture the others and drag them out of the uterus back up into the female’s oviduct. Some embryos also die earlier because they get strangled in the ropelike bodies of the other embryos. The female reabsorbs any embryos that die.

*asterisked references discuss homosexuality/transgender

Bromley, P. T. (1991) “Manifestations of Social Dominance in Pronghorn Bucks.” Applied Animal Behavior Science 29:147–64.

Bromley, P. T., and D. W. Kitchen (1974) “Courtship in the Pronghorn Antilocapra americana.” In V. Geist and F. Walther, eds., The Behavior of Ungulates and Its Relation to Management, vol. 1, pp. 356–74. IUCN Publication no. 24. Morges, Switzerland: International Union for Conservation of Nature and Natural Resources.

Geist, V. (1990) “Pronghorns.” In Grzimek’s Encyclopedia of Mammals, vol. 5, pp. 282–85. New York: McGraw-Hill.

Geist, V., and P. T. Bromley (1978) “Why Deer Shed Antlers.” Zeitschrift für Säugetierkunde 43:223–31.

*Gilbert, B. K. (1973) “Scent Marking and Territoriality in Pronghorn (Antilocapra americana) in Yellowstone National Park.” Mammalia 37:25–33.

*Kitchen, D. W. (1974) “Social Behavior and Ecology of the Pronghorn.” Wildlife Monographs 38:1-96.

O’Gara, B. W. (1978) “Antilocapra americana.” Mammalian Species 90:1–7.

———(1969) “Unique Aspects of Reproduction in the Female Pronghorn (Antilocapra americana Ord.)” American Journal of Anatomy 125:217–32.

Kob society is complex and is organized around two types of social systems: sex-segregated herds and LEKS. Outside of the breeding grounds, the antelopes congregate in same-sex herds: bachelor herds contain 400–600 males, while female herds usually have 30–50 adults (as well as young of both sexes), though they can contain as many as 1,000 antelopes. On the breeding grounds, the population is structured into a dozen or more small territories known as leks. These are small arenas that the males—and occasionally females—use for performing intricate courtship displays, and which they defend against the intrusion of other males. Females leave their herds to visit these leks, where they choose males to mate with and also interact sexually with other females. The other Kob antelopes also live in sex-segregated female and bachelor herds, although some Lechwe herds are cosexual. In addition, a few males—who do the most mating—are territorial, while some Waterbuck males are SATELLITES, associating with territorial males and occasionally mating with females.

Behavioral Expression: Virtually all Kob females engage in some form of homosexual activity, ranging from simple sexual mounting of other females all the way up to elaborate courtship displays. These interactions usually take place when the females are in heat and may occur either in the female herds or on the leks. Homosexual courtship and sexual interactions consist of a rich array of stylized movements in a fixed sequence, which are all used in heterosexual courtship as well. Individual females vary in how many of these display behaviors they employ when courting another female—some use only one or two, while others employ the full repertoire. A female usually begins her homosexual courtship by PRANCING: she approaches another female with short, stiff-legged steps, her head held high and tail raised. This is followed by an action known as FLEHMEN or LIP-CURLING: she sniffs the vulva of the other female, who crouches and urinates while her partner places her nose in the stream of urine. While doing this, she retracts her upper lip in a curling gesture, exposing a special sexual scenting organ that allows her to sample the odor of the urine. Her courtship dance continues with a stylized gesture known as FORELEG KICKING: she raises her foreleg and gently touches the other female between her legs from behind. The other female responds with ritual MATING-CIRCLING, in which she circles tightly around the courting female, sometimes nipping or butting her hindquarters. This leads to mounting, in which the first female stands on her hind legs and climbs on top of the other from behind, as in heterosexual mating. Sometimes the mounting female gives a single vigorous pelvic thrust, similar to the thrusting that a male makes when he reaches orgasm.

Homosexual copulation may be followed by a further display of stylized behaviors. The courting female, for example, might make a distinctive whistling sound by forcing air loudly through her nostrils with her mouth closed (also made by males in heterosexual courtship). The two females may also engage in what is known as INGUINAL NUZZLING: the female who was mounted adopts a special posture with her hind legs spread wide, tail raised, back arched, and her neck extended in a graceful swanlike position. The other Kob licks her partner’s vulva and udder from behind and then concentrates on nuzzling and licking two special “inguinal glands” located in the same region, which secrete a pungent, waxy substance. Finally, the interaction concludes with what is known as the PINCERS MOVEMENT, in which one female gently holds the other in a “pincers” position with her head on the other Kob’s back and her leg raised underneath her belly. Occasionally, a female Kob will herd other females and even defend her display territory against courting males by attacking the males head-on—no small feat, considering that she does not have the horns that most males use for such purposes. The majority of Kob that participate in homosexual mounting also become pregnant and raise young—and in all cases, this is done in the female-only herds, with little or no participation from males beyond insemination.

Female homosexual mounting also occurs in three other closely related species of antelopes, the Waterbuck, Lechwe, and Puku. Interestingly, Waterbuck females that mount each other are not usually in heat, unlike Kob. Occasionally, a Waterbuck female will perform courtship flehmen with another female as well. Hermaphrodite or intersexual individuals also sometimes occur in Kob: one animal, for example, was chromosomally male and had testes and large horns, combined with a vagina, uterus, and enlarged clitoris.

Frequency: Homosexual mounting is common among Kob. Each female participates in same-sex mounting about twice an hour (on average) during the mating season, and over an entire mating season a female might mount other females 60 or more times (although most females probably engage in this activity a dozen or so times). However, because heterosexual mounting rates are extraordinarily high—more than seven times higher than homosexual rates—same-sex mounting accounts for only about 9 percent of all sexual activity. Homosexual courtship displays are less common than same-sex mounting in this species. In Puku and Lechwe, mounting between females is also common, but it occurs only occasionally among Waterbuck.

Orientation: Most, if not all, female Kob are bisexual, participating in both heterosexual and homosexual mounting, but individuals vary along a continuum in their orientation. For some, same-sex mounting makes up nearly 60 percent of their sexual activity, while for others it constitutes only 1–3 percent, but the average is about 11 percent. Fewer Kob females use courtship displays with other females, but there is a parallel range in variation. About 7 percent of females employ a significant portion of the full courtship repertoire when interacting with other females. In the other species of Kob antelopes, females that engage in homosexual mounting probably also participate in heterosexual activities as well.

As described above, Kob society is sex-segregated, and there are large numbers of nonbreeding animals, particularly among males. Only a relatively small proportion of males (about 5 percent) have access to lek territories at one time, and only some of these will be selected by females to mate with. In some populations of Waterbuck, large numbers of males are also nonbreeders: at any given time, only 7 percent of males are territory holders, 9 percent are satellites, and the remainder live in bachelor herds. In fact, only 20 percent of males in this species become territorial during their lives. Although a few satellite and bachelor males mate with females, the majority do not. Female Kob usually mate repeatedly with their chosen males—generally many more times than is required to become pregnant—and may copulate with up to nine different males when they visit the lek. Waterbuck females also mate repeatedly when in heat, usually with the same male each time. Kob heterosexual copulations are often preceded by numerous nonreproductive mounts in which the male does not have an erection. Furthermore, full penetration may not occur during copulation, and often the male does not ejaculate even when he does achieve penetration. Waterbuck males sometimes mount females from the side or other positions where penetration cannot occur. When all types of mounts are considered, the rate of heterosexual activity in Kob is staggering: during a 24-hour visit to the lek, each female may engage in several hundred mountings, 40 of which will be full copulations. Female Lechwe are often chased and harassed by males (especially nonterritorial ones) trying to mate with them. Sometimes several males will disrupt a heterosexual copulation, and only 8 percent of matings in cosexual herds and 42 percent on leks result in ejaculation.

*asterisked references discuss homosexuality/transgender

Balmford, A., S. Albon, and S. Blakeman (1992) “Correlates of Male Mating Success and Female Choice in a Lek-Breeding Antelope.” Behavioral Ecology 3:112–23.

*Benirschke, K. (1981) “Hermaphrodites, Freemartins, Mosaics, and Chimaeras in Animals.” In C. R. Austin and R. G. Edwards, eds., Mechanisms of Sex Differentiation in Animals and Man, pp. 421–63. London: Academic Press.

Buechner, H. K., J. A. Morrison, and W. Leuthold (1966) “Reproduction in Uganda Kob, with Special Reference to Behavior.” In I. W. Rowlands, ed., Comparative Biology of Reproduction in Mammals, pp. 71–87. Symposia of the Zoological Society of London no. 15. London: Academic Press.

Buechner, H. K., and H. D. Roth (1974) “The Lek System in Uganda Kob.” American Zoologist 14:145–62.

*Beuchner, H. K., and R. Schloeth (1965) “Ceremonial Mating Behavior in Uganda Kob (Adenota kob thomasi Neumann).” Zeitschrift für Tierpsychologie 22:209–25.

*DeVos, A., and R. J. Dowsett (1966) “The Behavior and Population Structure of Three Species of the Genus Kobus. Mammalia 30:30–55.

Leuthold, W. (1966) “Variations in Territorial Behavior of Uganda Kob Adenota kob thomasi (Neumann 1896).” Behavior 27:214–51.

Morrison, J. A., and H. K. Buechner (1971) “Reproductive Phenomena During the Post Partum-Preconception Interval in the Uganda Kob.” Journal of Reproduction and Fertility 26:307–17.

Nefdt, R. J. C. (1995) “Disruptions of Matings, Harassment, and Lek-Breeding in Kafue Lechwe Antelope.” Animal Behavior 49:419–29.

Rosser, A. M. (1992) “Resource Distribution, Density, and Determinants of Mate Access in Puku.” Behavioral Ecology 3:13–24.

*Spinage, C. A. (1982) A Territorial Antelope: The Uganda Waterbuck. London: Academic Press.

———(1969) “Naturalistic Observations on the Reproductive and Maternal Behavior of the Uganda Defassa Waterbuck Kobus defassa ugandae Neumann.” Zeitschrift für Tierpsychologie 26:39–47.

Wirtz, P. (1983) “Multiple Copulations in the Waterbuck (Kobus ellipsiprymnus).” Zeitschrift für Tierpsychologie 61:78–82.

———(1982) “Territory Holders, Satellite Males, and Bachelor Males in a High-Density Population of Waterbuck (Kobus ellipsiprymnus) and Their Associations with Conspecifics.” Zeitschrift für Tierpsychologie 58:277–300.

Blackbucks live in small, same-sex herds containing 10–50 individuals. Female herds circulate within the territory of one or several adult males who mate with them; the remaining males live in “bachelor” herds on the periphery of the breeding territories. Thomson’s and Grant’s Gazelles have a similar social organization, except that mixed herds containing both males and females also form, especially during migration.

Behavioral Expression: The majority of male Blackbucks have homosexual interactions: among all age groups, mounting of one male by another occurs in the position used for heterosexual intercourse. Usually mounting happens during play-fighting—friendly sparring matches with erotic overtones, sometimes involving three males at a time. In addition, adult males often perform courtship displays toward adolescent males (one-to-two-year-olds) prior to mounting them. These displays, which also occur in heterosexual interactions, begin with the older male DISPLAY WALKING: he stands some distance away from the object of his attentions, lowering his ears and curling his tail up to touch his back. He walks in this posture parallel to the younger male so that the younger one has to walk in a circle. This is followed by PRESENTING THE THROAT: the older male raises his nose high in the air so that his spiral horns touch the back of his neck. This exposes the striking black-and-white pattern of his neck. While doing this, he briskly kicks first one foreleg, then the other, in front of him several times in a row, sometimes reaching under the other male’s belly or between his thighs. Occasionally, the older male makes a distinctive barking sound as he does this. This is then followed by mounting of the younger male by the older. Occasionally, female Blackbucks mount other females.

In Thomson’s Gazelles, male homosexual mounting may occur in a variety of contexts, including during migration and in encounters between two nonterritorial males. Males also occasionally direct courtship displays toward one another, including the NECK-STRETCH, FORELEG KICK, and NOSE-UP POSTURE, as well as the PURSUIT MARCH (the latter similar to heterosexual courtships). Homosexual courtship displays are preceded by one or both males displaying their horns to the other (often interpreted as a threatening gesture). Homosexual mounting in Grant’s Gazelles typically occurs as part of a formalized display in which two males march toward one another, lifting their heads high and showing their white throat patches when they are next to each other. The mounted male, if an adult, often attacks the male trying to mount him (females also sometimes respond aggressively to a male’s advances, see below).

Frequency: Male homosexual activity is common among Blackbucks: at any given time, fully three-quarters of the male population lives in the bachelor herds, where most homosexual interactions take place. Among Thomson’s and Grant’s Gazelles, homosexual behavior is much less frequent: 12 percent of encounters between male Grant’s involve mounting, while 1–8 percent of encounters between male Thomson’s involve sexual behavior.

Orientation: All Blackbuck males over three years old leave the bachelor herd temporarily to attempt mating with females. However, this usually occurs only once or twice in each male’s lifetime; for the remainder of his life, he interacts homosexually. Technically, then, all male Blackbuck are bisexual, though in practice they are predominantly homosexual. In Thomson’s Gazelles, homosexual mounting typically occurs among males in bachelor or migratory groups, not territorial males (who are involved principally in heterosexual activities). Although these males occasionally court and attempt to mount females, the majority of their sexual interactions may be with other males. In Grant’s males, homosexual behavior does occur in some territorial males; since these males direct sexual behaviors toward both males and females, they are functionally bisexual (although males generally do not consent to being mounted by other males).

Because of the organization of Blackbuck society into sex-segregated herds and the small number of active breeding males, only a fraction of the male population is ever involved in heterosexual activity. Furthermore, although all males attempt to leave the bachelor herds and mate with females, most are unable to do so because of the males already defending the breeding territories; consequently life in the bachelor herd is preferable for many males. Among Grant’s and Thomson’s Gazelles, there are similar patterns of sex segregation and nonparticipation in heterosexuality—in fact, more than 90 percent of the male Grant’s population may be composed of nonbreeders at any given time. In addition, female Grant’s Gazelles often behave aggressively toward males during heterosexual courtship, performing threat displays and sometimes even fighting bucks to fend off unwanted advances. Female Blackbucks sometimes engage in nonreproductive mounts of fawns or young animals.

*asterisked references discuss homosexuality/transgender

*Dubost, G., and F. Feer (1981) “The Behavior of the Male Antilope cervicapra L., Its Development According to Age and Social Rank.” Behavior 76:62–127.

*Schaller, G. B. (1967) The Deer and the Tiger. Chicago: University of Chicago Press.

Walther, F. R. (1995) In the Country of Gazelles. Bloomington: Indiana University Press.

*———(1978a) “Quantitative and Functional Variations of Certain Behavior Patterns in Male Thomson’s Gazelle of Different Social Status.” Behavior 65:212–40.

*———(1978b) “Forms of Aggression in Thomson’s Gazelle; Their Situational Motivation and Their Relative Frequency in Different Sex, Age, and Social Classes.” Zeitschrift für Tierpsychologie 47:113–72.

*———(1974) “Some Reflections on Expressive Behavior in Combats and Courtship of Certain Horned Ungulates.” In V. Geist and F. Walther, eds., Behavior in Ungulates and Its Relation to Management, vol. 1, pp. 56–106. IUCN Publication no. 24. Morges, Switzerland: International Union for Conservation of Nature and Natural Resources.

———(1972) “Social Grouping in Grant’s Gazelle (Gazella granti Brooke, 1827[sic])” in the Serengeti National Park.” Zeitschrift für Tierpsychologie 31:348–403.

*———(1965) “Verhaltensstudien an der Grantgazelle (Gazella granti Brooke, 1872) im Ngorogoro-Krater [Behavioral Studies on Grant’s Gazelle in the Ngorogoro Crater].” Zeitshcrift für Tierpsychologie 22:167-208.

WILD SHEEP, GOATS, AND BUFFALO

Mountain Sheep live in sex-segregated bands, usually numbering 5–15 individuals. During the rutting season, the sexes intermingle and mate promiscuously (males copulate with multiple partners and do not form long-term pair-bonds or participate in parenting).

Behavioral Expression: In Bighorn and Thinhorn Sheep, males live in what one zoologist has described as “homosexual societies” where same-sex courtship and sexual activity occur routinely among all rams. Typically an older, higher-ranking male will court a male younger than him, using a sequence of stylized movements. Same-sex courtship is often initiated when one male approaches the other in the LOW-STRETCH posture, in which the head and neck are lowered and extended far forward. This might be combined with the TWIST, where the male sharply rotates his head and points his muzzle toward the other male, often while flicking his tongue and making growling or grumbling sounds. The courting ram often performs a FORELEG KICK, stiffly snapping his front leg up against the other male’s belly or between his hind legs. He also occasionally sniffs and nuzzles the other male’s genital area and may perform LIP-CURLING or FLEHMEN, in which he samples the scent of the other male’s urine by retracting his upper lip to expose a special olfactory organ. Thinhorn rams may even lick the penis of the male they are courting. The male being courted sometimes rubs his forehead and cheeks on the other ram’s face—even licking and nibbling him—and may also rub his horns on the other male’s neck, chest, or shoulders, occasionally developing an erection. Similar courtship behaviors occur among male Asiatic Mouflons.

In addition to genital licking (in Thinhorns), sexual activity between rams usually involves mounting and anal intercourse: typically the larger male rears up on his hind legs and mounts the smaller male, placing his front legs on the other’s flanks. The mountee assumes a characteristic posture known as LORDOSIS, in which he arches his back to facilitate the copulation (this posture is also seen in many female mammals during heterosexual mating). Usually the mounting male has an erect penis and achieves full anal penetration, performing pelvic thrusts that probably lead to ejaculation in many cases. Mounting and courtship interactions between males sometimes also take place in groups known as HUDDLES: three to ten rams cluster together in a circle, rubbing, nuzzling, licking, horning, and mounting each other. Usually huddles are non-aggressive interactions in which all males are willing participants; occasionally, though, several rams in a huddle focus all their attentions on the same (usually smaller) male, taking turns mounting him and even chasing him if he tries to get away. Female Mountain Sheep also occasionally participate in sexual activity with one another, including licking each other’s genitals, mounting, and occasional courtship activities.

So pervasive and fundamental is same-sex courtship and sexuality in Bighorns and Thinhorns that females are said to “mimic” males in order to mate with them. They adopt the behavior patterns typical of younger males being courted by older males, thereby sparking sexual interest on the part of rams because, ironically, they now resemble males. In another twist on gender roles and sexuality, there are also occasionally “female-mimicking” males in some populations—but notably, such males do not typically participate in homosexual mounting and courtship. Transgendered males are physically indistinguishable from other rams, but behaviorally they resemble females. They remain in the sex-segregated ewe herds year-round, they often adopt the crouching urination posture typical of females, and they are lower-ranking and less aggressive than most males and even many females (even though they are often larger in body and horn size, the typical criteria used to establish rank). Most significantly, transgendered rams do not usually allow other males to court or mount them. Again, this is a typically female pattern, since ewes in these species generally do not permit rams to court or mount them except for the few days out of each year when they are in heat.

Frequency: In Bighorns and Thinhorns, homosexual mounting occurs commonly throughout the year, but is especially frequent during the rut when heterosexual activity is also taking place, accounting for about a quarter of all sexual activity at that time (and occurring in up to 69 percent of males’ interactions with each other). Outside of the rut, all mounting activity is homosexual, but mounting only accounts for 2–3 percent of males’ interactions with each other. Among females, 1–2 percent of interactions include mounting. At least 70 percent of males’ interactions with one another involve courtship behaviors. Homosexual activity appears to be less frequent in Asiatic Mouflons: it is seen sporadically in wild animals, while in captivity about 10 percent of mounting and some courtship behaviors occur between animals of the same sex, mostly females. Behavioral transvestism occurs in approximately 5 percent of rams in some populations of Bighorn Sheep.

Orientation: Virtually all male Bighorn and Thinhorn Sheep participate in homosexual courtship and mounting; the extent to which they also engage in heterosexual pursuits during the rut varies with their age and rank. Younger, lower-ranking rams—close to half of the male population—rarely get to mate with females at all, and some of these males have only homosexual relations. Among older, higher-ranking rams, heterosexual behavior is much more common—but even when they are courting and mounting females, it is often because of the malelike behavior patterns that the females are using (as described above). In other words, even in their heterosexuality, Mountain Sheep may be decidedly “homosexual.”

Large portions of the male population in Bighorn and Thinhorn Sheep do not breed (as mentioned above). Although many younger and lower-ranking males try to mount females, they are able to mate less than 20 percent of the time because both females and higher-ranking rams will not usually allow them to complete their copulations. However, nonbreeding rams actually have a much lower mortality rate than breeding males—nearly six times lower—owing to the stresses of reproduction (including fasting during the breeding season, fights and chases, and other major energy expenditures). Ewes often reject the advances of older, higher-ranking rams as well (nearly 65 percent of the time in Bighorns), and this may lead to harassment and even forced copulations or rapes. In fact, rams employ three distinct strategies to try to mate with females, only one of which entails courtship and consensual copulations. TENDING involves a ram following a particular female for short periods of time, during which he courts her and is usually permitted to mate. COURSING consists of a ram chasing and sometimes butting a female, who is usually forced to copulate under threat of further punishment from the ram. BLOCKING involves forcefully cornering and trapping females with threats and more violent actions such as horn butts; ewes may be knocked down or bounced against trees if they try to escape and have been sequestered for up to nine days at a time by blocking rams. Almost half of all ewes in heat, on average, experience the trauma of blocking. Rams also sometimes mount lambs as well as females who are not in heat—in all, about 15 percent of heterosexual mounts are on such nonfertilizable partners. Male Mountain Sheep “masturbate” by crouching, protruding the penis sideways past the front legs, and ejaculating (sometimes after nuzzling the penis or rubbing it against the front leg). As described above, Mountain Sheep society is strongly sex-segregated for the majority of the year. Since rams and ewes only associate for two months or so during the rut, females usually raise their young on their own with no help from males. Occasionally, however, a ewe who has lost her own lamb will help another mother suckle her young. Such “helpers” are more common among higher-ranking females, where up to 30 percent of mothers who have lost their lambs may foster-nurse other youngsters.

Same-sex courtship and mounting occur in several other species of wild sheep and goats, involving similar behavior patterns to those found in North American and European wild sheep. Among Bharal or Blue Sheep (Pseudois nayaur) of the Himalayas, 36–57 percent of mounting occurs between males (sometimes in huddles), while approximately 11 percent of courtship displays such as the low-stretch, twist, and foreleg kick are performed between males. Males also perform a “penis display” toward other males, in which the animal sometimes licks or sucks his own organ. Male Markhor (Capra falconeri) and Wild Goats or Bezoar (Capra aegagrus), two Central Asian species, also occasionally court and mount other males, as do male and female Aoudad or Barbary Sheep (Ammotragus lervia) of North Africa.

*asterisked references discuss homosexuality/transgender

*Berger, J. (1985) “Instances of Female-Like Behavior in a Male Ungulate.” Animal Behavior 33:333-35.

Demarchi, D. A., and H. B. Mitchell (1973) “The Chilcotin River Bighorn Population.” Canadian Field-Naturalist 87:433–54.

Festa-Bianchet, M. (1991) “The Social System of Bighorn Sheep: Grouping Patterns, Kinship, and Female Dominance Rank.” Animal Behavior 42:71–82.

*Geist, V. (1975) Mountain Sheep and Man in the Northern Wilds. Ithaca, N.Y.: Cornell University Press.

*———(1971) Mountain Sheep: A Study in Behavior and Evolution. Chicago: University of Chicago Press.

*———(1968) “On the Interrelation of External Appearance, Social Behavior, and Social Structure of Mountain Sheep.” Zeitschrift für Tierpsychologie 25:199–215.

*Habibi, K. (1987a) “Behavior of Aoudad (Ammotragus lervia) During the Rutting Season.” Mammalia 51: 497–513.

*———(1987b) “Overt Sexual Behavior Among Female Aoudads.” Southwestern Naturalist 32:148.

Hass, C. C. (1991) “Social Status in Female Bighorn Sheep (Ovis canadensis): Expression, Development, and Reproductive Correlates.” Journal of Zoology, London 225:509-23.

*Hass, C. C, and D. A. Jenni (1991) “Structure and Ontogeny of Dominance Relationships Among Bighorn Rams.” Canadian Journal of Zoology 69:471-76.

*Hogg, J. T. (1987) “Intrasexual Competition and Mate Choice in Rocky Mountain Bighorn Sheep.” Ethology 75:119–44.

———(1984) “Mating in Bighorn Sheep: Multiple Creative Male Strategies.” Science 225:526-29.

*Katz, I. (1949) “Behavioral Interactions in a Herd of Barbary Sheep (Ammotragus lervia).” Zoologica 34:9–18.

*McClelland, B. E. (1991) “Courtship and Agonistic Behavior in Mouflon Sheep.” Applied Animal Behavior Science 29:67-85.

*Pfeffer, P. (1967) “Le mouflon de Corse (Ovis ammon musimon, Schreber 1782). Position systématique, écologie, et éthologie comparées [The Mouflon of Corsica: Comparative Systematics, Ecology, and Ethology].” Mammalia (suppl.) 31:1–262.

*Schaller, G. B. (1977) Mountain Monarchs: Wild Sheep and Goats of the Himalaya. Chicago: University of Chicago Press.

*Schaller, G. B., and Z. B. Mirza (1974) “On the Behavior of Punjab Urial (Ovis orientalis punjabiensis).” In V. Geist and F. Walther, eds. The Behavior of Ungulates and Its Relation to Management, vol. 1, pp. 306-23. IUCN Publication no. 24. Morges, Switzerland: International Union for Conservation of Nature and Natural Resources.

*Shackleton, D. M. (1991) “Social Maturation and Productivity in Bighorn Sheep: Are Young Males Incompetent?” Applied Animal Behavior Science 29: 173–84.

Valdez, R. (1990) “Oriental Wild Sheep.” In Grzimek’s Encyclopedia of Mammals, vol. 5, pp. 544–48. New York: McGraw-Hill.

*WiIson, P. (1984) “Aspects of Reproductive Behavior of Bharal (Pseudois nayaur) in Nepal.” Zeitschrift für Säugetierkunde 49:36–42.

Musk-oxen are generally social animals, living in mixed-sex herds (usually 10–20 animals) or smaller all-male groups; some males are also solitary. Male and female Mountain Goats remain largely segregated from each other for most of the summer, females associating in groups of usually less than 15 (including their offspring). Female Mountain Goats are generally dominant to males, who are solitary or peripheral to the female groups except during the rut. The mating system for both species is polygamous or promiscuous: animals copulate with several partners, and males do not participate in parenting.

Behavioral Expression: Male Musk-oxen sometimes court and mount each other. Homosexual courtship involves several of the same patterns used in heterosexual interactions: POSITIONING, in which one male stands next to the other in a standard position such as perpendicular, parallel, or head-to-tail; SNIFFING OF THE REAR, in which one male smells and inspects the anal and genital region of the other; FORELEG KICKING, where one male gently swings his front leg against another male; and CHIN-RESTING, in which the courting male places his lower jaw on top of the other male’s body. Males also mount other males from behind (as in heterosexual mating). The mounted male sometimes resists (as do females when mounted by males) but may also permit himself to be mounted. Homosexual courtship and mounting both occur among younger males, while during the rutting season adult males sometimes court younger males as well (occasionally even juveniles). Adult male Musk-oxen may also form pairlike companionships that travel, graze, and spend time together (sometimes also fighting with one another), although overt courtship and sexual behavior probably does not occur between them.

Adult male Mountain Goats court younger (yearling) males, again using the species-typical heterosexual behavior patterns: the courting male approaches the other in a crouching position, creeping on his stomach with his head stretched forward (a posture referred to as the LOW-STRETCH). He may also flick his tongue in and out of his mouth while making a soft buzzing sound, jerk his head sideways, and attempt to lick the other male’s flanks. Typically the yearling male responds aggressively to the courting adult. Adult males occasionally perform this display toward other adult males as well. In addition, yearling females sometimes mount their own mothers.

Frequency: In captive Musk-oxen, about 40 percent of courtship behavior and 10 percent of mounting activity is homosexual. A little over a quarter of wild, nonbreeding males associate in pairs. In Mountain Goats, nearly 18 percent of courtships during the breeding season are between adult and yearling males; about 8 percent of courtship displays outside of the breeding season occur between two adult males. In one study, 1 out of 14 mounts (7 percent) performed by yearling Mountain Goats on their mothers were same-sex, involving a female offspring.

Orientation: Some younger male Musk-oxen may participate exclusively in homosexual activity, since most males do not breed until they are older than six. In contrast, yearling male Mountain Goats that are courted by older males are primarily heterosexual, since they reject most same-sex advances. The majority of adult male Musk-oxen and Mountain Goats that court other males are probably bisexual, since they also court females and usually do so more often than they court males.

Although male Musk-oxen become sexually mature by the time they are two years old, most bulls do not mate heterosexually for another five years because older males generally monopolize breeding opportunities in the female herds. Even among older males, less than half—and often as few as one-quarter—actually participate in procreation. The remainder are nonbreeding bulls that are often solitary or associate with other males in pairs or small groups, sometimes wandering far from the herds. The rate of calf production is low in this species (females usually reproduce every other year), and entire populations may forgo breeding in some years. Even during breeding years, some heterosexual courtship activity in both Muskoxen and Mountain Goats may be directed by males toward nonprocreating individuals such as yearlings and calves. In addition, male Mountain Goats sometimes court and mount females outside the breeding season or even court females in the act of giving birth. Females in this species have been observed mounting adult males and courting, mounting, or being mounted by their own yearlings or kids. Relations between the sexes are often marked by strife. Females of both species sometimes reject the courtship and mounting attempts of males. Male Musk-oxen may become violent during their courtship kicks of females (the impact of the blow against a female’s spine or pelvis can be considerable). As many as two-thirds of Musk-ox mounts may not culminate in ejaculation, because the male is anatomically unsuited to remaining mounted on the female (he is considerably heavier than her and unable to clasp with his forelegs during a mount). Among Mountain Goats, females are often notably aggressive toward males, attacking and sometimes viciously wounding them with stabs from their sharp horns. In addition, violence toward calves has been observed among Musk-oxen: females sometimes flip calves other than their own into the air with their horns, while males have been known to gore calves.

In the distantly related Himalayan Tahr (Hemitragus jemlahicus), intersexuality sometimes occurs: one individual, for example, had testes and the general appearance of a male combined with a vulva, enlarged clitoris, and a female chromosome pattern.

*asterisked references discuss homosexuality/transgender

*Benirschke, K. (1981) “Hermaphrodites, Freemartins, Mosaics, and Chimaeras in Animals.” In C. R. Austin and R. G. Edwards, eds., Mechanisms of Sex Differentiation in Animals and Man, pp. 421–63. London: Academic Press.

Chadwick, D. H. (1983) A Beast the Color of Winter: The Mountain Goat Observed. San Francisco: Sierra Club Books.

*———(1977) “The Influence of Mountain Goat Social Relationships on Population Size and Distribution.” In W. Samuel and W. G. Macgregor, eds., Proceedings of the First International Mountain Goat Symposium, pp. 74–91. Victoria, B. C.: Fish and Wildlife Branch.

*Geist, V. (1964) “On the Rutting Behavior of the Mountain Goat.” Journal of Mammalogy 45:551–68.

Gray, D. R. (1979) “Movements and Behavior of Tagged Muskoxen (Ovibos moschatus) on Bathurst Island, N.W.T.” Musk-ox 25:29–46.

———(1973) “Social Organization and Behavior of Muxkoxen (Ovibos moschatus) on Bathurst Island, N.W.T.” Ph.D. thesis, University of Alberta.

*Hutchins, M. (1984) “The Mother-Offspring Relationship in Mountain Goats (Oreamnos americanus).” Ph.D. thesis, University of Washington.

Jingfors, K. (1984) “Observations of Cow-Calf Behavior in Free-Ranging Muskoxen.” In D. R. Klein, R. G. White, and S. Keller, eds., Proceedings of the First International Muskox Symposium, pp. 105–9. Biological Papers of the University of Alaska Special Report no. 4. Fairbanks: University of Alaska.

Lent, P. C. (1988) “Ovibos moschatus.” Mammalian Species 302:1–9.

*Reinhardt, V. (1985) “Courtship Behavior Among Musk-ox Males Kept in Confinement.” Zoo Biology 4:295–300.

*Smith, T. E. (1976) “Reproductive Behavior and Related Social Organization of the Muskox on Nunivak Island.” Master’s thesis, University of Alaska.

*Tener, J. S. (1965) Muskoxen in Canada: A Biological and Taxonomic Review. Ottawa: Canadian Wildlife Service.

Adult males (bulls) in American and European Bison generally live separately from females in groups that may contain up to 12 animals, or else solitarily. Females, their calves, and younger males (generally less than three or four years old) all live together in their own groups. For two months out of the year, female groups aggregate and adult males join these larger herds (which may contain hundreds of animals) for the rutting season. The mating system is “serial monogamy” within an overall framework of polygamy, i.e., males mate with several females, but remain exclusively with each female for a short period. African Buffalo have a similar social organization, living in herds ranging in size from 40–1,500 animals, mostly composed of females and their young in family groups, along with some adult males for part of the year. In addition, about 15 percent of adult males live in smaller bachelor herds, and older males may form peripheral groups.

Behavioral Expression: Male American Bison participate in a variety of homosexual activities. Among younger bulls (less than five years old, particularly one-to-three-year-olds), anal intercourse is common. One male mounts the other with an erect penis and achieves anal penetration; the animal being mounted often facilitates the sexual interaction by positioning his hips or backing toward the other male with his tail lifted to the side. Homosexual copulation lasts on average nearly twice as long as heterosexual mating. The same bull may be mounted several times in succession by one or several other males, but reciprocal mounting is less common, since bulls that mount other males often do not allow themselves to be mounted (although males that are mounted do try to mount their partners). Males that are frequently mounted by other males often exhibit tears in the skin on their back where the mounting bull’s hooves rub on either side of their spine. An identical type of skin abrasion is seen in female Bison that are frequently mounted by males. Homosexual mounting also occurs in a number of other contexts: in Bison (both American and European) and African Buffalo, males sometimes mount each other during play-fighting. An adult male American Bison may also mount another bull at the conclusion of an aggressive interaction. In these two contexts, mounting usually does not involve penetration, although erection of the penis and pelvic thrusting may occur. Sometimes one male will rest his chin on the other’s rump as a prelude to mounting, often while making a soft panting sound. Female homosexual mounting and CHIN-RESTING also occur in Wisent and African Buffalo.

American Bison bulls—especially younger males—also sometimes form a TENDING BOND or consortship with another male. This paired association resembles the temporary (from a few hours to several days) monogamous bond formed between males and females during the rutting season. In a homosexual tending, one male closely follows and defends another male and may mount him as well. In some pairs mounting is reciprocal; in others, only one partner mounts or is mounted. In addition, younger males sometimes form “tending groups” of four to five individuals who take turns mounting one another or the same individual. Homosexual tending groups are unique in the joint participation of all the males in sexual activity: although several males often accompany heterosexual tending pairs, they never participate in sexual activity with either member of the pair.

Among American Bison, various types of intersexuality or hermaphroditism occasionally occur spontaneously in nature. Some transgendered individuals are known as BUFFALO ox and grow to be extraordinarily tall—they may be one and a half times bigger than a nontransgendered bull and generally have shorter fur as well. Other intersexual individuals are intermediate in size between males and females, possess malelike horns, and have female external genitalia and a uterus combined with testes. During tending bonds, these animals interact with both males and females: one individual tended females the way a (heterosexual) male would, but was also tended by other bulls as in heterosexual and homosexual interactions.

Frequency: Homosexual mounting is very prevalent among American Bison bulls, especially during the rutting season, when it may be seen several times a day. In fact, homosexual mounting is more common than heterosexual mounting in this species, since each female rarely mates with a male more than once a year, while each male may engage in same-sex mounting many times a day. The behavior is especially frequent among younger males, peaking in three-year-olds. Studies of semiwild populations have found that more than 55 percent of mounting in younger males is same-sex, and for some age categories all mounting behavior may be homosexual. It is less common among older adult males and three-to-four-year-olds. Female homosexual mounting in Bison and African Buffalo, as well as male same-sex mounting in African Buffalo, occurs occasionally.

Orientation: In American (and probably also European) Bison, younger bulls—nearly two-thirds of the male population—are functionally bisexual, although many actually participate exclusively in homosexual activity. It was once thought that such males only engage in homosexual mounting because older bulls prevent their access to females; however, studies on captive herds have shown that bulls still participate extensively in homosexual activity even when older bulls are not present. Older bulls, as well as females in Wisent and African Buffalo, are probably functionally bisexual but primarily heterosexual, with many individuals never engaging in homosexual activity.

As noted above, large portions of the Bison bull population do not breed: males of both the American and European species are sexually mature by the time they are three years old, yet they do not get a chance to breed until they are six and large enough to compete with older males. Even among older bulls, more than a quarter do not copulate heterosexually during the rutting period, and as many as 15 percent of females may not breed in a given year. In Wisent and African Buffalo, there are some postreproductive males and females as well—older individuals who have ceased breeding in the later years of their life. Nonprocreative sexual activities also figure in the social lives of heterosexual Bison: female American Bison often mount the male during tending, for example, and male Wisent occasionally ejaculate by rubbing the penis against the female’s flanks. More than 20 percent of American Bison females engage in repeated copulations (only a single mating is necessary for procreation), and Wisent females have been observed mating with the same male eight times within half an hour. Wisent females also occasionally copulate during pregnancy (as late as three to four days before birth), and heterosexual activity sometimes occurs outside the breeding season. In American Bison, a notable separation and even hostility often exists between the sexes. As mentioned above, males and females live apart from one another for most of the year; during the rutting season, females frequently refuse the advances of males, and females often bear the scars of repeated heterosexual matings (described above). Wisent family life is occasionally marked by violence or abuse: calves have been killed by rutting bulls, and females sometimes desert their calves (especially those born late in the calving season).

Among feral Water Buffalo (Bubalus bubalis) in Australia, female homosexual mounting is common: all cows mount other cows in heat, with 15–20 percent of the female population participating at any given time.

*asterisked references discuss homosexuality/transgender

Caboń-Raczyńska, K., M. Krasinska, and Z. Krasiński (1983) “Behavior and Daily Activity Rhythm of European Bison in Winter.” Acta Theriologica 28:273–99.

*Caboń-Raczyńska, K., M. Krasinska, Z. Krasiński, and J. M. Wójcik (1987) “Rhythm of Daily Activity and Behavior of European Bison in the Białowieża Forest in the Period without Snow Cover.” Acta Theriologica 32:335-72.

*Jaczewski, Z. (1958) “Reproduction of the European Bison, Bison bonasus (L.), in Reserves.” Acta Theriologica 1:333–76.

*Komers, P. E., F. Messier, and C. C. Gates (1994) “Plasticity of Reproductive Behavior in Wood Bison Bulls: When Subadults Are Given a Chance.” Ethology Ecology & Evolution 6:313–30.

*———(1992) “Search or Relax: The Case of Bachelor Wood Bison.” Behavioral Ecology and Sociobiology 31:195–203.

Krasinska, M., and Z. A. Krasiński (1995) “Composition, Group Size, and Spatial Distribution of European Bison Bulls in Bialowieza Forest.” Acta Theriologica 40:1–21.

*Krasiński, Z., and J. Raczyński (1967) “The Reproduction Biology of European Bison Living in Reserves and in Freedom.” Acta Theriologica 12:407-44.

*Lott, D. F. (1996–7) Personal communication.

*———(1983) “The Buller Syndrome in American Bison Bulls.” Applied Animal Ethology 11:183–86.

———(1981) “Sexual Behavior and Intersexual Strategies in American Bison (Bison bison).” Zeitschrift für Tierpsychologie 56:115–27.

*———(1974) “Sexual and Aggressive Behavior of Adult Male American Bison (Bison bison).” In V. Geist and E Walther, eds., Behavior in Ungulates and Its Relation to Management, vol. 1, pp. 382–94. Morges, Switzerland: International Union for Conservation of Nature and Natural Resources.

*Lott, D. F., K. Benirschke, J. N. McDonald, C. Stormont, and T. Nett (1993) “Physical and Behavioral Findings in a Pseudohermaphrodite American Bison.” Journal of Wildlife Diseases 29: 360–63.

*McHugh, T. (1972) The Time of the Buffalo. New York: Knopf.

*———(1958) “Social Behavior of the American Buffalo (Bison bison bison).” Zoologica 43:1–40.

*Mloszewski, M. J. (1983) The Behavior and Ecology of the African Buffalo. Cambridge: Cambridge University Press.

*Reinhardt, V. (1987) “The Social Behavior of North American Bison.” International Zoo News 203:3–8.

*———(1985) “Social Behavior in a Confined Bison Herd.” Behavior 92:209–26.

*Roe, F. G. (1970) The North American Buffalo: A Critical Study of the Species in Its Wild State. Toronto: University of Toronto Press.

*Rothstein, A., and J. G. Griswold (1991) “Age and Sex Preferences for Social Partners by Juvenile Bison Bulls.” Animal Behavior 41:227–37.

*Sinclair, A. R. E. (1977) The African Buffalo: A Study of Resource Limitation of Populations. Chicago: University of Chicago Press.

*Tulloch, D. G. (1979) “The Water Buffalo, Bubalus bubalis, in Australia: Reproductive and Parent-Offspring Behavior.” Australian Wildlife Research 6:265–87.

OTHER HOOFED MAMMALS

Mountain and Plains Zebras have two main social units: breeding groups containing a herd stallion and three to five females with their offspring, and nonbreeding or “bachelor” groups. Groups combine to form herds numbering in the tens of thousands in Plains Zebras. Little is known of Takhi social organization in the wild, where the species is extinct (although it is beginning to be reintroduced from cap-418 tive populations). It is likely that they have a system similar to that of Mountain and Plains Zebras, including both bachelor and “harem” herds.

Behavioral Expression: Mounting between male Mountain Zebras is prefaced by a special ritualized display or “greeting” ceremony performed by two herd stallions, combining elements of courtship and sexual behaviors similar to those in heterosexual interactions. When two herd stallions meet, they approach each other with a stiff, high-stepping walk, holding their heads erect and ears forward as a friendly gesture. The males then rub first their noses and then their bodies together. Body rubbing is done either with the stallions facing in the same direction, or with one male’s head at the other’s rump. In the latter position, one male may nuzzle and sniff the other’s genitals with his muzzle. Finally, one stallion sometimes mounts the other, or they may take turns mounting each other; occasionally a male will walk a few steps while another stallion is mounted on him. Plains Zebra males have also been observed placing their head on the rump of another male, a ritualized movement (also found in heterosexual courtship) that is thought to indicate an intention to mount the other male. When a herd stallion meets a bachelor male, many of the same behaviors occur, except for mounting. In addition, the bachelor male displays a distinctive facial expression resembling that used by Zebra mares in heat—lowering the head and pulling the lips and mouth corners back to expose the teeth—combined with a high-pitched call. Bachelor males also “greet” each other this way, often leading to play-fighting in which the males gently bite at each other and rear up on their hind legs. Bachelor males also sometimes mount each other as part of play-fighting.

Takhi mares occasionally mount each other; in some cases, pregnant females perform this sexual behavior with other females. Mares may mount each other from a sideways position in addition to from behind (the usual position for heterosexual mounting, although younger males also sometimes use a lateral mounting position). Such females may be among the highest-ranking mares in the herd and can also be noticeably aggressive toward males, kicking or biting them when the latter try to court other females.

Frequency: In captivity, mounting and attempted mounting occur in about 60 percent of interactions between male Plains Zebras. Among wild Mountain Zebras, homosexual interactions are less frequent. About 20 percent of play interactions between bachelor males involve mounting, while herd stallions associate with bachelor males (including “greetings” interactions) about 5 percent of the time. Female homosexual mounting in Takhi occurs occasionally (in captivity).

Orientation: In Zebras, herd stallions that engage in homosexual mounting and courtshiplike “greeting” behavior with other males also court and mate with females. Bachelor males, on the other hand, are exclusively homosexual to the extent that they engage in such behaviors, since they do not generally participate in heterosexual activity while in the bachelor herds. A little more than half of the male population of Mountain Zebras consists of bachelor males; most males join bachelor herds when they are just under two years old and stay for an average of two and a half years. About half of all bachelor males go on to become herd stallions and therefore are sequentially bisexual. However, some males remain in the bachelor herds for their entire lives, never mating heterosexually. Among Takhi, at least some females that mount other females are functionally bisexual, since they may be pregnant when they engage in homosexual activity.

As noted above, a large proportion of the male population in Zebras, as well as in Takhi, are nonbreeding bachelors. Some female Zebras also join the bachelor herds and do not participate in heterosexual activity while there (they remain for just under a year, on average). Wild equids also engage in an assortment of nonprocreative heterosexual activities. Males of all three species sometimes perform heterosexual mounts without an erection or penetration, while Takhi mares sometimes REVERSE mount stallions. Male Mountain Zebras and Takhi also frequently masturbate by erecting the penis and flipping it against the belly. Female equids sometimes also engage in an activity known as CLITORAL WINKING as part of courtship, in which the clitoris is rhythmically erected and wetted against the labia (often in conjunction with urination). Mountain Zebras occasionally participate in incestuous copulations: both father-daughter and brother-sister matings have been documented, although generally such pairings are avoided because females leave their family’s herd before they reach sexual maturity. In addition, male Plains Zebras often try to mate with unrelated juvenile females that are not yet sexually mature. In fact, stallions—alone or in groups of up to 18 at a time—may “abduct” adolescent females by separating and chasing them from their family groups, after which they will try to copulate with the young mares. Interestingly, the female shows the behavioral signs of being “in heat” before she reaches the age when she can actually conceive; usually an “abducted” mare returns to her family group after her period of “heat” is finished. In contrast, in Takhi it is often the females who behave aggressively toward males (as mentioned above).

In these equids, a number of violent behaviors are also directed toward young foals. Mountain Zebra and Takhi stallions occasionally kill foals; in the latter species, infanticide occurs when the male grabs the youngster by its neck, shaking it and tossing it into the air. Female Mountain Zebras also sometimes accidentally kill their foals by kicking them; ironically, this may occur when they are trying to defend them from other mares, who are often aggressive toward unrelated foals. However, in a few cases females have adopted an unrelated foal, and in one instance a female even rejected her own offspring and adopted another. A Plains Zebra mare may also allow another mare’s foal to suckle from her. Although Takhi males are not as involved in parenting as mares, a stallion may act as a “surrogate mother” to his own foal if it has lost its mother, even allowing the foal to “suckle” on his penis sheath.

asterisked references discuss homosexuality/transgender

*Boyd, L. E. (1991) “The Behavior of Przewalski’s Horses and Its Importance to Their Management.” Applied Animal Behavior Science 29:301–18.

*———(1986) “Behavior Problems of Equids in Zoos.” In S. L. Crowell-Davis and K. A. Houpt, eds., Behavior, pp. 653–64. The Veterinary Clinics of North America: Equine Practice 2(3). Philadelphia: W. B. Saunders.

*Boyd, L. E. and K. A. Houpt (1994) “Activity Patterns.” In L. Boyd and K. A. Houpt, eds., Przewalski’s Horse: The History and Biology of an Endangered Species, pp. 195–227. Albany: State University of New York Press.

Houpt, K. A., and L. Boyd (1994) “Social Behavior.” In L. Boyd and K. A. Houpt, eds. Przewalski’s Horse: The History and Biology of an Endangered Species, pp. 229–54. Albany: State University of New York Press.

Klingel, H. (1990) “Horses.” In Grzimek’s Encyclopedia of Mammals, vol. 4, pp. 557-94. New York: McGraw-Hill.

———(1969) “Reproduction in the Plains Zebra, Equus burchelli boehmi: Behavior and Ecological Factors.” Journal of Reproduction and Fertility, suppl. 6:339-45.

Lloyd, P. H., and D. A. Harper (1980) “A Case of Adoption and Rejection of Foals in Cape Mountain Zebra, Equus zebra zebra.” South African Journal of Wildlife Research 10:61–62.

Lloyd, P. H., and O. A. E. Rasa (1989) “Status, Reproductive Success, and Fitness in Cape Mountain Zebra (Equus zebra zebra).” Behavioral Ecology and Sociobiology 25:411–20.

*McDonnell, S. M., and J. C. S. Haviland (1995) “Agonistic Ethogram of the Equid Bachelor Band.” Applied Animal Behavior Science 43:147-88.

Monfort, S. L., N. P. Arthur, and D. E. Wildt (1994) “Reproduction in the Przewalski’s Horse.” In L. Boyd and K. A. Houpt, eds., Przewalski’s Horse: The History and Biology of an Endangered Species, pp. 173-93. Albany: State University of New York Press.

*Penzhorn, B. L. (1984) “A Long-term Study of Social Organization and Behavior of Cape Mountain Zebras Equus zebra zebra.” Zeitschrift für Tierpsychologie 64:97–146.

Rasa, O. A. E., and P. H. Lloyd (1994) “Incest Avoidance and Attainment of Dominance by Females in a Cape Mountain Zebra (Equus zebra zebra) Population.” Behavior 128:169-88.

Ryder, O. A., and R. Massena (1988) “A Case of Male Infanticide in Equus przewalskii.” Applied Animal Behavior Science 21:187–90.

*Schilder, M. B. H. (1988) “Dominance Relationships Between Adult Plains Zebra Stallions in Semi-Captivity.” Behavior 104:300–319.

Schilder, M. B. H., and P. J. Boer (1987) “Ethological Investigations on a Herd of Plains Zebra in a Safari Park: Time-Budgets, Reproduction, and Food Competition.” Applied Animal Behavior Science 18:45–56.

van Dierendonck, M. C., N. Bandi, D. Batdorj, S. Dügerlham, and B. Munkhtsag (1996) “Behavioral Observations of Reintroduced Takhi or Przewalski Horses (Equus ferus przewalskii) in Mongolia.” Applied Animal Behavior Science 50:95–114.

Warthogs tend to associate in matriarchal groups (also known as SOUNDERS) of several females and their offspring, and in all-male “bachelor” groups. Only 3 percent of groups contain both males and females, and many Warthog males are solitary. Males join female groups only briefly for mating, which is usually promiscuous—both males and females copulate with multiple partners—and the only long-lasting bonds that form are between animals of the same sex, primarily females. Collared Peccaries live in herds of 5–15 individuals, containing animals of both sexes.

Behavioral Expression: Homosexual mounting occurs in both Collared Peccaries and Warthogs. In Collared Peccaries, females in heat often RIDE or mount other females, and males occasionally mount one another as well. In Warthogs, homosexual mounting also takes place among females in heat, though it is less common. Sometimes a female Warthog will mount another female from the side, a position that is also occasionally used in heterosexual mounting. Warthog females often develop long-lasting bonds with each other, and same-sex mounting can be a part of these pairings (stable male-female pairs do not occur in this species). The two females associate together for many years and may even jointly raise their young, combining their litters and suckling each other’s offspring. In addition, when one female is injured or temporarily unable to look after her young, the other female will take over parental duties. One such pair was seen consistently chasing away males who tried to get close to them. Biologists studying Warthogs call these pairs or groups of adult females without any males or offspring SPINSTER groups—they typically contain an older female with a younger one. Some of these pairings involve related females, such as sisters or mother and daughter—in which case some same-sex mounting may be incestuous—although nonrelated pairings also occur. Occasionally two male Warthogs pair off as well, though no sexual behavior has been observed between them.

Frequency: Homosexual mounting occurs commonly in Collared Peccaries during heat; it is less frequent in Warthogs, probably comprising 1–3 percent of all mountings. About 5 percent of all Warthog groups are “spinster” (female-only) groups.

Orientation: Females that participate in same-sex mounting are probably bisexual, since most also engage in heterosexual relations. Warthog female companions, for example, may mate with males and reproduce, even if they do not consistently socialize with males. More than a quarter of Warthog females do not get pregnant each season, however, so it is possible that some are involved exclusively in same-sex (bonding and/or sexual) activities.

Significant portions of Warthog populations do not procreate. In addition to the nonbreeding females and sex-segregated groups mentioned above, one- and two-year-olds that are sexually mature may remain with their mother’s group to help raise additional litters (rather than breeding themselves). These two species also participate in a variety of nonreproductive sexual behaviors. About 6 percent of heterosexual activity in Collared Peccaries, for example, involves females mounting males (REVERSE mounts), while another 22 percent of copulations are incomplete mounts by males. Males also frequently mount females during nonfertile periods, including pregnancy. Male Warthogs have been observed spontaneously ejaculating, including in their sleep. In addition, opposite-sex mountings in both species sometimes consist of a male mounting the female from the side without actual penetration (about 2 percent of sexual behavior in Collared Peccaries). Moreover, insemination does not necessarily occur even if penetration does, due to VAGINAL PLUGS. In both Collared Peccaries and Warthogs, a gelatinous barrier in the female’s reproductive tract is deposited by a male when he copulates, very likely insuring that sperm from any subsequent matings cannot impregnate the female. Since female Warthogs usually copulate with more than one male, and female Collared Peccaries often mate repeatedly with the same male (as many as 18 times in three hours), a large proportion of copulations are therefore probably nonprocreative. Females can also refuse copulations by covering the vulva with their tail and tightening their leg muscles upward. In Collared Peccaries, offspring are cared for not only by their biological mothers, but also by “nursemaids,” usually older sisters of the youngsters, that defend and nurse them. Often the nursemaids are not in fact sexually mature—they may be as young as six months old—with the amazing consequence that many nursemaids are themselves still nursing from their own “nursemaids.” It is thought that they are able to produce milk because they consume the mother’s placenta when she gives birth, perhaps thereby receiving some sort of hormonal influence from the mother. In Warthogs a number of violent counterreproductive activities also occur: adult males occasionally kill their younger brothers or cannibalize other males that they kill.

Same-sex mounting also occurs in White-lipped Peccaries (Tayassu pecari) among both males and females.

*asterisked references discuss homosexuality/transgender

Bissonette, J. A. (1982) Ecology and Social Behavior of the Collared Peccary in Big Bend National Park, Texas. Scientific Monograph Series no. 16. Washington, D.C.: U.S. National Park Service.

Byers, J. A., and M. Bekoff (1981) “Social, Spacing, and Cooperative Behavior of the Collared Peccary, Tayassu tajacu.” Journal of Mammalogy 62:767–85.

Child, G., H. H. Roth, and M. Kerr (1968) “Reproduction and Recruitment Patterns in Warthog (Phacochoerus aethiopicus) Populations.” Mammalia 32:6–29.

Cumming, D. H. M. (1975) A Field Study of the Ecology and Behavior of Warthog. Salisbury, Rhodesia: Trustees of the National Museums and Monuments of Rhodesia.

*Dubost, G. (1997) “Comportements comparés du Pécari à levres blanches, Tayassu pecari, et du Pécari à collier, T. tajacu (Artiodactylea, Tayassuidés) [Comparative Behaviors of the White-lipped Peccary and of the Collared Peccary (Artiodactyla, Tayassuidae)].” Mammalia 61:313–43.

Frädrich, H. (1965) “Zur Biologie und Ethologie des Warzenschweines (Phacochoerus aethiopicus Pallas), unter Beriicksichtigung des Verhaltens anderer Suiden [On the Biology and Ethology of Warthogs, in View of the Behavior of Other Suidae].” Zeitschrift für Tierpsychologie 22:328–93.

Packard, J. M., K. J. Babbitt, K. M. Franchek, and P. M. Pierce (1991) “Sexual Competition in Captive Collared Peccaries (Tayassu tajacu).” Applied Animal Behavior Science 29:319–26.

Schmidt, C. R. (1990) “Peccaries.” In Grzimek’s Encyclopedia of Mammals, vol. 5, pp. 48–55. New York: McGraw-Hill.

*Somers, M. J., O. A. E. Rasa, and B. L. Penzhorn (1995) “Group Structure and Social Behavior of Warthogs Phacochoerus aethiopicus.” Acta Theriologica 40:257–81.

*Sowls, L. K. (1997) Javelinas and Other Peccaries: Their Biology, Management, and Use. College Station: Texas A&M University Press.

*———(1984) The Peccaries. Tucson: University of Arizona Press.

*———(1974) “Social Behavior of the Collared Peccary Dicotyles tajacu (L.).” In V. Geist and F. Walther, eds., The Behavior of Ungulates and Its Relation to Management, vol. 1, pp. 144–65. IUCN Publication no. 24. Morges, Switzerland: International Union for Conservation of Nature and Natural Resources.

*———(1966) “Reproduction in the Collared Peccary (Tayassu tajacu).” In I. W. Rowlands, ed., Comparative Biology of Reproduction in Mammals, Symposia of the Zoological Society of London no. 15, pp. 155–72. London and New York: Academic Press.

Torres, B. (1993) “Sexual Behavior of Free-Ranging Amazonian Collared Peccaries (Tayassu tajacu.)” Mammalia 57:610–13.

Vicuñas live in cosexual groups usually containing 1 male, 3–10 females, and their offspring. In addition, all-male groups are a regular feature of Vicuña populations; they usually contain 5–10 animals, but may swell to include more than 150 individuals.

Behavioral Expression: Female Vicuñas sometimes mount each other, with one animal straddling the other’s back with her forelegs. This is similar to a heterosexual mating, except the mounted animal does not typically lie down as she would if a male were mounting her (even in heterosexual interactions, though, the female does not always cooperate by lying down). In one case, a pregnant female chased another female and mounted her. Adolescent males also sometimes mount one another during play-fighting, remaining astraddle for up to a quarter of a minute. Play-fights are gentle frolics in which the two males push and wrestle each other with their heads and long necks, interspersed with chasing or rearing on the hind legs.

Frequency: Same-sex mounting probably occurs only sporadically in Vicuñas. However, heterosexual mating is also infrequent: during a seven-month study period, for example, 5–11 heterosexual matings were observed compared to one mount between females.

Orientation: At least some females that mount other females are bisexual, since this behavior occurs in pregnant females. During the time that adolescent males are living in bachelor groups, the majority of their mounting activities are same-sex. Many of these males will go on to mate heterosexually, although about 10 percent of the nonbreeding animals in male bands are adults.

About 40 percent of Vicuñas do not breed: many are younger males living in the sex-segregated male groups (although these also include some adults), and there are solitary older animals as well. Among breeding animals, there is often considerable antagonism between the sexes: males have been known to fight with pregnant females, and territorial males are openly hostile toward females from neighboring bands, often chasing and attacking them. During copulation, females sometimes refuse to lie down; a male may try to force his partner to mate by bringing his full weight onto her back, causing the female to stagger underneath him. Adult males occasionally copulate with yearling females, who are probably not old enough to breed. Sexual activity between males and females also takes place outside of the breeding season.

*asterisked references discuss homosexuality/transgender

Bosch, P. C., and G. E. Svendsen (1987) “Behavior of Male and Female Vicuna (Vicugna vicugna Molina 1782) as It Relates to Reproductive Effort.” Journal of Mammalogy 68:425–29.

Carwardine, M. (1981) “Vicuna.” Wildlife 23:8–11.

Franklin, W. L., (1983) “Contrasting Socioecologies of South America’s Wild Camelids: The Vicuna and Guanaco.” In J. F. Eisenberg and D. G. Kleiman, eds., Advances in the Study of Mammalian Behavior, pp. 573–629. American Society of Mammalogists Special Publication no. 7. Stillwater, Okla.: American Society of Mammalogists.

———(1974) “The Social Behavior of the Vicuna.” In V. Geist and F. Walther, eds., The Behavior of Ungulates and Its Relation to Management, vol. 1, pp. 477–87. IUCN Publication no. 24. Morges, Switzerland: International Union for Conservation of Nature and Natural Resources.

Franklin, W. L., and W. Herre (1990) “South American Tylopods.” In Grzimek’s Encyclopedia of Mammals, vol. 5, pp. 96–111. New York: McGraw-Hill.

*Koford, C. B. (1957) “The Vicuna and the Puna.” Ecological Monographs 27:153–219.

Elephants have a complex and highly organized community life. Females usually live in matriarchal herds of up to 50 individuals (loosely organized into family groups) led by an older female and generally containing no permanent adult males. Bulls often form male-only herds of 7–15 individuals (particularly in the African species), but may also be loners. Breeding males associate only temporarily with the female herds and mate with several different females.

Behavioral Expression: Both African and Asiatic Elephant males participate in homosexual mounting. Among African Elephants, same-sex activity—which often takes place at or in watering holes—may be preceded by a great deal of caressing and affectionate behaviors. Two males intertwine their trunks, gently nudge each other, touch mouths in a “kiss,” place their trunk tips in each other’s mouth, roll over one another, and generally frolic together (sometimes with erections). One male often signals his intention to mount by extending his trunk along the other male’s back, sometimes pushing him forward with his tusks (a gesture also used in sexual interactions between males and females). Homosexual mounting may also be preceded by one male sniffing or touching the other’s penis with the tip of his trunk. Mounting occurs in the typical heterosexual position, with one male behind the other, and often the mounting male has an erect penis. Homosexual mating lasts about the same length as heterosexual mating, generally less than a minute, although one male may mount another several times in succession. Both older bulls and younger males participate in this activity. Among Asiatic Elephants, same-sex mounting sometimes occurs as part of play-fighting, in which two males swing their trunks at each other and gently rush at and butt one another. In African Elephants living in bull herds, a form of “erotic combat” also occurs. Two males push against each other while locking tusks and intertwining trunks; this activity stimulates the males sexually, and they develop full erections over up to half a dozen such bouts. Mounting sometimes occurs following a bout.

Although female homosexual activity has not yet been observed among wild Elephants, in captivity females sometimes masturbate one another with their trunks (the female’s clitoris is nearly 17 inches long when erect or engorged). In addition, both female and male Asiatic Elephants in captivity engage in a variety of same-sex interactions with one another, including mounting activities and touching of the genitals with the trunk. Pregnant females also sometimes participate in these interactions.

Male Elephants also form “companionships,” usually composed of an older bull and an attendant younger male (in contrast, there are no long-lasting heterosexual bonds in these species). In African Elephants, the younger male often helps the older one by guarding him or pulling down branches for him; in other cases, the older bull may help a younger male (or vice versa) who is injured or suffering from blindness or paralysis. The two males are constant companions and generally isolated from other Elephants; occasionally, an older bull will have two younger attendants. Among Asiatic Elephants, such male companionships appear not to be as long-lasting as in African Elephants. Younger attendant males in African Elephants are sometimes reported to have enlarged genitalia.

Frequency: In wild African and Asiatic Elephants, homosexual mounting is a fairly common and regular occurrence, especially among younger bulls. In addition, Asiatic Elephant males spend an average of 10 percent of their time in play-fighting (which can also include mounting between males), while individual African Elephant bulls may participate in erotic combat up to four or five times a day during some times of the year. Approximately 18 percent of male Asiatic Elephants (not living in mixed-sex herds) have a male companion. In captivity, about 11 percent of social interactions between male Asiatic Elephants involve sexual activities, compared to approximately a quarter of social interactions between females; overall, roughly 45 percent of sexual interactions involve same-sex participants.

Orientation: Some younger Asiatic Elephant males that participate in homosexual activity are bisexual, since they may direct their sexual attentions to both males and females. However, some males are probably exclusively homosexual for at least part of their lives, since many Asiatic and African males do not participate in heterosexual activity until they are much older. African Elephant males in companionships are also exclusively same-sex oriented, since they are nonbreeders.

Elephant heterosexual life is frequently characterized by segregation and even antagonism between the sexes. In Asiatic Elephants, males and females often live separate from each other: males only associate with female herds about 25—30 percent of the time, and approximately 60 percent of the herds are not accompanied by males. As described above, Elephant herd structure is matriarchal, and females have even developed alternative parenting and “baby-sitting” arrangements without the contribution of males. Asiatic Elephant mothers often leave their calves in “nursery groups” that the adult females take turns looking after, allowing the other mothers to forage on their own. Female African Elephants often look after and occasionally even suckle other calves in their matriarchal groups. Furthermore, in both African and Asiatic species males experience a periodic sexual cycle known as MUSTH. A male in musth exhibits a number of characteristic physiological and behavioral changes, including increased aggression, ear waving and head swinging, infrasonic rumbling calls, continuous urinal discharge, and secretion by the temporal glands (located on either side of the head). Musth can last a few days to several months; during this time, males tend to associate more with females, but once musth is over, they usually return to male-only groups. Among African Elephants, bulls frequent special areas during their nonmusth time where their interactions are exclusively with other males, and they sometimes form a stronger association with one or two particular bulls.

During heterosexual interactions, females may be overtly aggressive toward males. Female Asiatic Elephants, for example, often charge and chase males (especially younger ones) that are trying to mate with them. In addition, males sometimes try to mount juvenile animals, who squeal in protest until a female intervenes. In fact, it is thought that female aggressiveness toward males contributes to a significant delay in breeding in this species: although males are sexually mature when about 10 years old, most do not begin breeding until about 17 years old. Reproductive suppression also occurs in African Elephants: the onset of puberty in females may be delayed by up to 10 years in some populations as a result of social, nutritional, or physiological stresses. In addition, most males do not father their first offspring until they are 30—35 years old—this is 15—20 years after they become sexually mature. Other nonbreeding individuals include loner males (often older, postreproductive individuals), males in “companionships” (described above), as well as postreproductive or menopausal females (generally older than 50 years), and females who have nonbreeding intervals of up to 13 years between calves. Heterosexual relations are further complicated by an apparent mismatch in the structure of the male and female genitalia: unlike in most mammals, the female’s vaginal opening is placed far forward on her belly, hampering access by the male. Although his penis is able to assume a special S-shape to reach her vulva, penetration is often difficult to achieve. On occasion, the male’s organ will contact the female’s anus rather than her vulva, and he may ejaculate before achieving penetration. Heterosexual relations also often include touching and stimulation of the genitals with the trunk; in captivity, one female was also observed rubbing her clitoris against a male’s side while he was lying down.

Homosexual mounting in the Indian Rhinoceros (Rhinoceros unicornis) has been observed among adolescent females in captivity.

asterisked references discuss homosexuality/transgender

*Buss, I. O. (1990) Elephant Life: Fifteen Years of High Population Density. Ames, Iowa: Iowa State University Press.

Buss, I. 0,. and N. S. Smith (1966) “Observations on Reproduction and Breeding Behavior of the African Elephant.” Journal of Wildlife Management 30:375—88.

*Dixon, A., and M. MacNamara (1981) “Observations on the Social Interactions and Development of Sexual Behavior in Three Sub-adult, One-horned Indian Rhinoceros (Rhinoceros unicornis) Maintained in Captivity.” Zoologische Garten 51:65—70.

Douglas-Hamilton, I., and O. Douglas-Hamilton (1975) Among the Elephants. London: Collins & Harvill.

Eisenberg, J. F., G. M. McKay, and M. R. Jainudeen (1971) “Reproductive Behavior of the Asiatic Elephant (Elephas maximus maximus L.).” Behavior 38:193—225.

*Grzimek, B. (1990) “African Elephant.” In Grzimek’s Encyclopedia of Mammals, vol. 4, pp. 502—20. New York: McGraw-Hill.

*Jayewardene, J. (1994) The Elephant in Sri Lanka. Colombo, Sri Lanka: Wildlife Heritage Trust of Sri Lanka.

*Kühme, W. (1962) “Ethology of the African Elephant (Loxodonta africana Blumenbach 1797) in Captivity.” International Zoo Yearbook 4:113—21.

Laws, R. M. (1969) “Aspects of Reproduction in the African Elephant, Loxodonta africana.” Journal of Reproduction and Fertility, suppl. 6:193—217.

Lee, P. C. (1987) “Allomothering Among African Elephants.” Animal Behavior 35:278—91.

*McKay, G. M. (1973) Behavior and Ecology of the Asiatic Elephant in Southeastern Ceylon. Smithsonian Contributions to Zoology no. 125. Washington, D.C.: Smithsonian Institution Press.

*Morris, D. (1964) “The Response of Animals to a Restricted Environment.” Symposia of the Zoological Society of London 13:99—118.

Moss, C. (1988) Elephant Memories: Thirteen Years in the Life of an Elephant Family. New York: William Morrow and Co.

Moss, C., and J. H. Poole (1983) “Relationships and Social Structure of African Elephants.” In R. A. Hinde, ed., Primate Social Relationships: An Integrated Approach, pp. 315—25. Oxford: Blackwell Scientific Publications.

Poole, J. H. (1994) “Sex Differences in the Behavior of African Elephants.” In R. V. Short and E. Balaban, eds., The Differences Between the Sexes, pp. 331—46. Cambridge: Cambridge University Press.

———(1987) “Rutting Behavior in African Elephants: The Phenomenon of Musth.” Behavior 102:283— 316.

*Poole, T. B., V. J. Taylor, S. B. U. Fernando, W. D. Ratnasooriya, A. Ratnayeke, G. Lincoln, A. McNeilly, and A. M. V. R. Manatunga (1997) “Social Behavior and Breeding Physiology of a Group of Asian Elephants Elephas maximus at the Pinnawala Elephant Orphanage, Sri Lanka.” International Zoo Yearbook 35:297-310.

*Ramachandran, K. K. (1984) “Observations on Unusual Sexual Behavior in Elephants.” Journal of the Bombay Natural History Society 81:687—88.

*Rosse, I. C. (1892) “Sexual Hypochondriasis and Perversion of the Genetic Instinct.” Journal of Nervous and Mental Disease 19(11): 795—811.

*Shelton, D. J. (1965) “Some Observations on Elephants.” African Wild Life 19: 161—64.

*Sikes, S. K. (1971) The Natural History of the Elephant. New York: Elsevier Publishing Co.

CARNIVORES

Lions have two distinct forms of social organization. Some individuals are RESIDENTS, living in prides of up to a dozen or more adult females (usually all related to one another) with their cubs, along with an associated COALITION of one to nine adult males. Other Lions are NOMADS, ranging widely as solitary individuals or pairs. Female Cheetahs are largely solitary, while males are either RESIDENTS (with their own territories) or FLOATERS (without resident territories). Some males associate in groups of two to three (occasionally four) animals, often littermates (see below). The mating system is promiscuous or polygamous: males and females gen-432 erally mate with multiple partners, no long-term heterosexual bonds are formed, and males do not typically participate in parenting.

Behavioral Expression: In female Lions, homosexual interactions are often initiated by one female pursuing another and crawling under her to encourage the other female to mount her. When mounting another female, a Lioness displays a number of behaviors also associated with heterosexual mating, including gently biting the mountee on the neck, growling, making pelvic thrusts, and rolling on her own back afterward. Sometimes Lionesses take turns mounting each other. Because most females in a pride are related to each ther—on average about as closely related as cousins—homosexual behavior among Lionesses may be largely incestuous. Among male pride-mates (residents), homosexual activity often begins with a great deal of affectionate activity (which is also a component of “greetings” interactions between males). This includes mutual head-rubbing (often accompanied by a low moaning or humming noise), presentation of the hindquarters to the other male, sliding and rubbing against each other, circling one another, and rolling on the back with an erect penis. This may lead to intense caressing and eventually mounting of one male by the other, including pelvic thrusting. Sometimes three males rub and roll together, mounting each other in turn. A male Lion sometimes courts a particular individual, keeping company with him for several days while engaging in sexual behavior. He typically defends his partner against intruding males, and often other males in the group will join him in attacking any interfering males. Because male pride-mates, like females, are usually related to each other (as close, on average, as half brothers), this activity may also be incestuous. Nomadic male Lions also form long-lasting platonic “companionships” with other males, spending nearly all of their time together; these male pair- or trio-bonds are generally stronger than heterosexual bonds between residents. Companions are usually close in age; some are pride-mates or brothers, although about half of all companionships include unrelated individuals. Females occasionally form companionships with each other as well.

Female Cheetahs sometimes court other females, including participation in courtship chases, play-fighting, and mating circles. Courtship chases take place in the early morning, late afternoon, or on moonlit nights; groups of Cheetahs—in—cluding females—chase a female in heat for up to 150 yards. This may be interspersed with mock-fighting, in which the courting animals (females or males) rise up on their hind legs and drop their forelegs on the female being courted. Females also sometimes join MATING CIRCLES, where the animals lie in a circle around the courted female, often while the males take turns fighting each other. A female Cheetah may also mount another female who is in heat, clasping her with the forelegs, gently biting the scruff of her neck (as in heterosexual copulation), and thrusting against her. Male homosexual mounting occurs as well, and one male may also mount another male that is in the act of mating with a female. During courtship interactions, males also sometimes lick and nuzzle another male’s genitals while closely following him, occasionally exhibiting an erection while doing so.

Male Cheetahs often live in permanent partnerships or COALITIONS, consisting of a pair or trio of animals; about 30 percent of these associations include animals that are not related to each other, while the remainder consist of brothers. Partners are strongly bonded to one another and probably remain together for life. Spending almost all (93 percent) of their time in each other’s company, male pair-mates frequently groom one another (licking each other’s face and neck), defend each other in fights, and prefer resting together in close contact (even if this means that one of them will not be fully shaded against the harsh midday sun). Bonded males also become strongly distressed when separated, continuously searching and calling loudly for one another with birdlike yip or chirp calls. On being reunited, they may engage in a variety of affectionate and/or sexual activities, including reciprocal mounting with erections, face-rubbing, and STUTTERING (a purrlike vocalization often associated with sexual excitement). These activities appear to be more common between siblings than nonsiblings. Very rarely, paired males may temporarily adopt or look after lost cubs (most other parents in this species—foster or otherwise—are single mothers).

Frequency: In Lions, homosexual behavior in females is fairly common in captivity, while in the wild, two Lionesses were observed to mount each other three times over two days. In males, homosexual mounting may account for up to 8 percent of all mounting episodes. About 47 percent of all companionships involving adult nomadic Lions are between males, and about 37 percent are between females. Homosexual behavior (courtship and sexual) in Cheetahs is also quite frequent (at least in captive or semiwild conditions). In the wild, 27—40 percent of males live in same-sex pairs while 16—19 percent live in same-sex trios. In one study, 1 out of 11 instances of foster-parenting involved a pair of males looking after a cub (representing perhaps less than 1 percent of all families, adoptive and nonadoptive).

Orientation: Female Lions and male Cheetahs that participate in homosexual mounting may be bisexual, since same-sex activity sometimes alternates (or co-occurs) with heterosexual mounting in the same session. Some female Lions react aggressively to homosexual overtures and therefore these individuals are probably predominantly heterosexual. However, other females engage in same-sex mounting even in the presence of males, indicating more of a “preference” for homosexual activity. Many male Cheetahs living in partnerships do court and mate with females. However, pairs or trios of males are only with females 9 percent of the time, and they may experience reduced heterosexual mating opportunities compared to single males. Moreover, same-sex coalitions usually constitute life-long pair-bonds (which are not found between males and females in this species). Only about half of all companionships of two to three male Lions ever become residents that mate with a pride of females. Those that don’t may associate exclusively with other males for most of their lives, while some that do join a pride may participate in both same-sex and opposite-sex activities.

More than 60 percent of male Lions (solitary or in companionships) do not become residents during their lives and therefore do not participate in breeding. When they do, however, Lions have extraordinarily high heterosexual copulation rates. The female may mate as often as four times an hour when she is in heat over a continuous period of three days and nights (without sleeping), and sometimes with up to five different males—far in excess of the amount required if mating were simply for fertilization. A number of other nonprocreative sexual behaviors occur in these felids as well. Lions sometimes mate during pregnancy (up to 13 percent of all sexual activity), and as much as 80 percent of all heterosexual mating in some populations may not result in reproduction. In fact, following arrival of new males in a pride, females often increase their sexual activity while reducing their fertility (by failing to ovulate). In addition, “oral sex” is a feature of heterosexual foreplay—female Lions may lick and rub the male’s genitals, while Cheetahs of both sexes lick their partner’s genitals as part of heterosexual courtship. Male Lions have also been observed masturbating in captivity: an unusual technique is used, in which the Lion lies on his back and rolls his hindquarters up above his head, so that he can rub his penis with one of his front legs.

In wild Cheetahs, incestuous activity occasionally takes place when adult males try to mount their mothers, who typically react aggressively to such advances. In fact, heterosexual relations are in general characterized by a great deal of aggression between the sexes. In Lions, heterosexual copulation is often accompanied by snarling, biting, growling, and threats, and sometimes the female actually wheels around and slaps the male. During Cheetah courtship chases, males often knock females down and slap them, and these interactions may develop into full-scale fights. When the female is not in heat, the two sexes live largely segregated lives. Family life in these species may also be fraught with violence: infanticide occurs in Lions (where it accounts for more than a quarter of all cub deaths) as well as Cheetahs. Abandonment by their mother is the second highest cause of cub mortality in Cheetahs, and mother Cheetahs occasionally eat their own cubs if they have been killed by a predator (adult male Cheetahs also sometimes cannibalize each other). However, female Lions often participate in productive alternative family arrangements amongst themselves, such as communal care and suckling of young, as well as the formation of CRÈCHES or nursery groups. Female Cheetahs also sometimes (reluctantly) adopt orphaned or lost cubs.

*asterisked references discuss homosexualityltransgender

*Benzon, T. A., and R. F. Smith (1975) “A Case of Programmed Cheetah Acinonyx jubatus Breeding.” International Zoo Yearbook 15:154—57.

Bertram, B. C. R. (1975) “Social Factors Influencing Reproduction in Wild Lions.” Journal of Zoology, London 177:463—82.

*Caro, T. M. (1994) Cheetahs of the Serengeti Plains: Group Living in an Asocial Species. Chicago: University of Chicago Press.

*———(1993) “Behavioral Solutions to Breeding Cheetahs in Captivity: Insights from the Wild.” Zoo Biology 12:19—30.

*Caro, T. M., and D. A. Collins (1987) “Male Cheetah Social Organization and Territoriality.” Ethology 74:52—64.

*———(1986) “Male Cheetahs of the Serengeti.” National Geographic Research 2:75—86.

*Chavan, S. A. (1981) “Observation of Homosexual Behavior in Asiatic Lion Panthera leo persica.” Journal of the Bombay Natural History Society 78:363-64.

*Cooper, J. B. (1942) “An Exploratory Study on African Lions.” Comparative Psychology Monographs 17:1— 48.

Eaton, R. L. (1978) “Why Some Felids Copulate So Much: A Model for the Evolution of Copulation Frequency.” Carnivore 1:42—51.

*———(1974a) The Cheetah: The Biology, Ecology, and Behavior of an Endangered Species. New York: Van Nostrand Reinhold.

*———(1974b) “The Biology and Social Behavior of Reproduction in the Lion.” In R. L. Eaton, ed., The World’s Cats, vol. 2: Biology, Behavior, and Management of Reproduction, pp. 3–58. Seattle: Woodland Park Zoo.

*Eaton, R. L., and S. J. Craig (1973) “Captive Management and Mating Behavior of the Cheetah.” In R. L. Eaton, ed., The World’s Cats, vol. 1: Ecology and Conservation, pp. 217–254. Winston, Oreg.: World Wildlife Safari.

Herdman, R. (1972) “A Brief Discussion on Reproductive and Maternal Behavior in the Cheetah Acinonyx jubatus.” In Proceedings of the 48th Annual AAZPA Conference (Portland, OR), pp. 110–23. Wheeling, W. Va.: American Association of Zoological Parks and Aquariums.

Laurenson, M. K. (1994) “High Juvenile Mortality in Cheetahs (Acinonyx jubatus) and Its Consequences for Maternal Care.” journal of Zoology, London 234:387-408.

Morris, D. (1964) “The Response of Animals to a Restricted Environment.” Symposia of the Zoological Society of London 13:99–118.

Packer, C., L. Herbst, A. E. Pusey, J. D. Bygott, J. P. Hanby, S. J. Cairns, and M. B. Mulder (1988) “Reproductive Success of Lions.” In T. H. Clutton-Brock, ed., Reproductive Success: Studies of Individual Variation in Contrasting Breeding Systems, pp. 363–83. Chicago and London: University of Chicago Press.

Packer, C., and A. E. Pusey (1983) “Adaptations of Female Lions to Infanticide by Incoming Males.” American Naturalist 121:716–28.

———(1982) “Cooperation and Competition Within Coalitions of Male Lions: Kin Selection or Game Theory?” Nature 296:740–42.

Pusey, A. E., and C. Packer (1994) “Non-Offspring Nursing in Social Carnivores: Minimizing the Costs.” Behavioral Ecology 5:362–74.

*Ruiz-Miranda, C. R., S. A. Wells, R. Golden, and J. Seidensticker (1998) “Vocalizations and Other Behavioral Responses of Male Cheetahs (Acinonyx jubatus) During Experimental Separation and Reunion Trials.” Zoo Biology 17:1–16.

*Schaller, G. B. (1972) The Serengeti Lion. Chicago: University of Chicago Press.

Subba Rao, M. V., and A. Eswar (1980) “Observations on the Mating Behavior and Gestation Period of the Asiatic Lion, Panthera leo, at the Zoological Park, Trivandrum, Kerala.” Comparative Physiology and Ecology 5:78–80.

Wrogemann, N. (1975) Cheetah Under the Sun. Johannesburg: McGraw-Hill.

Red Fox society is characterized by highly complex and flexible living arrangements and social interactions, varying both between and within populations. Many Foxes live in groups with several, often related, adult females and one male (or rarely several); mated pairs are characteristic of other populations. Mating systems range from monogamy to polygamy. Wolves have a highly developed social system revolving around the pack, a group of usually a dozen or so individuals consisting of a mated pair and up to two generations of their offspring; occasionally, a few unrelated adults also live in the pack. Much less is known of the social life of wild Bush Dogs, although it appears that they, too, live in groups (possibly also pairs) and hunt in packs of usually a dozen individuals (though much larger groups containing hundreds of dogs have also been reported).

Behavioral Expression: When the breeding female in a Red Fox group comes into heat, both the male and female group members become sexually interested in her. Homosexual interactions involve the younger females—usually her daughters—running up to the vixen in heat, sniffing her genitals and mounting her. Although the mounting female clasps the other tightly, the older vixen usually responds to these sexual advances aggressively (as she does to most sexual approaches by males) by rearing up and “boxing” with the other female while gaping her mouth. The younger females may also mount each other, all the while making staccato, rasping click sounds known as GECKERING and SNIRKING. Pairs of Red Fox females also sometimes coparent their young, sharing a den, rearing their cubs together, bringing food for each other, and even suckling each other’s young. Although coparents are often related to each other, some may not be relatives.

Male Wolves often mount each other when the highest-ranking female in their pack comes into heat (a time when heterosexual activity also reaches its peak). As in Red Foxes, homosexual activity may be incestuous, since the males in the pack are often related to each other. A male Wolf sometimes also mounts another male when the latter is mounting a female. Male Bush Dogs have also been observed mounting each other, often accompanied by playful nipping of the legs or hindquarters.

Frequency: In captivity, homosexual mounting in Red Foxes and Wolves occurs frequently when the breeding female is in heat. In Bush Dogs, mounting between males is less common. The prevalence of these behaviors in the wild is not known.

Orientation: Many female Red Foxes that mount other females may be exclusively same-sex oriented, since such younger or lower-ranking individuals usually do not mate with males. For some females, this homosexual orientation may be longlasting—perhaps even continuing for a female’s entire life—since as many as 50–70 percent of vixens never leave their home groups to begin breeding on their own. Male Wolves that mount each other are bisexual, also showing sexual interest in females. However, their heterosexual activity is limited to the highest-ranking breeding female: males routinely ignore lower-ranking females in favor of homosexual activity.

In all three of these wild dog species, reproductive suppression is a prominent feature of the social system. For example, only a fraction of female Red Foxes reproduce—a third or more of all vixens (depending on the population) are non-breeders, and in some areas as many as 95 percent of adult females do not reproduce. There are multiple mechanisms for this “birth control.” In some cases, nonbreeding females simply do not mate, or else they fail to come into heat (a similar phenomenon occurs in Bush Dogs). In other cases, females become pregnant, but routinely abort their fetuses or abandon their young once they are born. Neglect or abuse of pups (leading to their death) has been documented in both Red Foxes and Bush Dogs, as well as cannibalism (in Red Foxes). In Wolves, the highest-ranking individuals (especially males) often prevent other animals from mating by intruding or attacking them directly; as many as a quarter of all mounts may be interrupted this way. In other cases, Wolves simply show no sexual interest in the opposite sex; these and other factors function to curtail reproduction in 40–80 percent of all packs. Breeding may also be inhibited by an incest taboo when a pack comes to consist entirely of closely related individuals (usually siblings). However, mother-son and brother-sister matings have occasionally been observed, and some packs may be highly inbred. In both Red Foxes and Wolves (and to a lesser extent, Bush Dogs), nonbreeding animals sometimes help the breeding female raise her young, including feeding, guarding, and “baby-sitting” them. There are even cases of a female Red Fox adopting an entire litter after their biological mother has died or been killed. However, some nonbreeding Red Foxes do not contribute any such care, and there is actually some evidence that more offspring may be successfully reared when there are fewer such “helpers” present in the group. Nonbreeding lone Wolves that do not act as helpers may constitute as much as 28 percent of some populations.

In addition to patterns of reproductive suppression, a number of nonreproductive heterosexual activities also occur in these canids. About 8 percent of female Red Foxes mate outside of the breeding period (this practice occurs in Wolves as well). Because males also have a sexual cycle ensuring that they cannot produce sperm during this time, such matings are definitively nonprocreative. About half of all heterosexual mounts in Wolves do not involve thrusting, penetration, or ejaculation; female Wolves also sometimes mount and thrust against males (REVERSE mounting). When mating does occur in Wolves and Red Foxes, individuals often engage in multiple copulations (i.e., more than the number of times simply required for fertilization). These often involve “copulatory ties” that keep the partners joined at the genitals for long periods. Heterosexual relations are sometimes fraught with difficulty, for example when female Red Foxes aggressively gape at males trying to mount them, or when both male and female Wolves display indifference or aggression toward animals trying to mate with them. In fact, one study showed that less than 3 percent of all heterosexual courtships in Wolves actually result in copulation.

Several forms of intersexuality or transgender occasionally occur in Raccoon Dogs (Nyctereutes procyonoides). Some individuals, for example, combine female genitals with testes, while others have a mosaic chromosome pattern that combines a male pattern (XY) with a joint male-female pattern (XXY).

*asterisked references discuss homosexuality/transgender

Creel, S., and D. Macdonald (1995) “Sociality, Group Size, and Reproductive Suppression Among Carnivores.” Advances in the Study of Behavior 24:203–57.

Derix, R., J. van Hooff, H. de Vries, and J. Wensing (1993) “Male and Female Mating Competition in Wolves: Female Suppression vs. Male Intervention.” Behavior 127:141-74.

Druwa, P. (1983) “The Social Behavior of the Bush Dog (Speothos).” Carnivore 6:46–71.

*Fentener van Vlissengen, J. M., M. A. Blankenstein, J. H. H. Thijssen, B. Colenbrander, A. J. E. P. Verbruggen, and C. J. G. Wensing (1988) “Familial Male Pseudohermaphroditism and Testicular Descent in the Raccoon Dog (Nyctereutes).” Anatomical Record 222:350–56.

van Hooff, J. A. R. A. M., and J. A. B. Wensing (1987) “Dominance and Its Behavioral Measures in a Captive Wolf Pack.” In H. Frank, ed., Man and Wolf: Advances, Issues, and Problems in Captive Wolf Research, pp. 219–52. Dordrecht: Dr W. Junk.

*Kleiman, D. G. (1972) “Social Behavior of the Maned Wolf (Chrysocyon brachyurus) and Bush Dog (Speothos venaticus): A Study in Contrast.” Journal of Mammalogy 53:791-806.

Lloyd, H. G. (1975) “The Red Fox in Britain.” In M. W. Fox, ed., The Wild Canids: Their Systematics, Behavioral Ecology, and Evolution, pp. 207–15. New York: Van Nostrand Reinhold.

Macdonald, D. W. (1996) “Social Behavior of Captive Bush Dogs (Speothos venaticus).” Journal of Zoology, London 239:525–43.

*———(1987) Running with the Fox. New York: Facts on File.

*———(1980) “Social Factors Affecting Reproduction Amongst Red Foxes (Vulpes vulpes L., 1758).” In E. Zimen, ed., The Red Fox: Symposium on Behavior and Ecology, pp. 123-75. Biogeographica no. 18. The Hague: Dr W. Junk.

———(1979) “‘Helpers’ in Fox Society.” Nature 282:69–71.

———(1977) “On Food Preference in the Red Fox.” Mammal Review 7:7–23.

Macdonald, D. W., and P. D. Moehlman (1982) “Cooperation, Altruism, and Restraint in the Reproduction of Carnivores.” In P. P. G. Bateson and P. H. Klopfer, eds., Perspectives in Ethology, vol. 5: Ontogeny, pp. 433–67.

Mech, L. D. (1970) The Wolf: The Ecology and Behavior of an Endangered Species. New York: Natural History Press.

Packard, J. M., U. S. Seal, L. D. Mech, and E. D. Plotka (1985) “Causes of Reproductive Failure in Two Family Groups of Wolves.” Zeitchrift für Tierpsychologie 68:24-40.

Packard, J. M., L. D. Mech, and U. S. Seal (1983) “Social Influences on Reproduction in Wolves.” In L. N. Carbyn, ed., Wolves in Canada and Alaska: Their Status, Biology, and Management, pp. 78–85. Canadian Wildlife Service Series no. 45. Ottawa: Canadian Wildlife Service.

Porton, I. J., D. G. Kleiman, and M. Rodden (1987) “Aseasonality of Bush Dog Reproduction and the Influence of Social Factors on the Estrous Cycle.” Journal of Mammalogy 68:867–71.

Schantz, T. von (1984) “‘Non-Breeders’ in the Red Fox Vulpes vulpes: A Case of Resource Surplus.” Oikos 42:59–65.

———(1981) “Female Cooperation, Male Competition, and Dispersal in the Red Fox Vulpes vulpes.” Oikos 37:63–68.

*Schenkel, R. (1947) “Ausdrucks-Studien an Wölfen: Gefangenschafts-Beobachtungen [Expression Studies of Wolves: Captive Observations].” Behavior 1:81-129.

Schotté, C. S., and B. E. Ginsburg (1987) “Development of Social Organization and Mating in a Captive Wolf Pack.” In H. Frank, ed., Man and Wolf: Advances, Issues, and Problems in Captive Wolf Research, pp. 349–74. Dordrecht: Dr W. Junk.

Sheldon, J. W. (1992) Wild Dogs: The Natural History of the Nondomestic Canidae. San Diego: Academic Press.

Smith, D., T. Meier, E. Geffen, L. D. Mech, J. W. Burch, L. G. Adams, and R. K. Wayne (1997) “Is Incest Common in Gray Wolf Packs?” Behavioral Ecology 8:384–91.

Storm, G. L., and G. G. Montgomery (1975) “Dispersal and Social Contact Among Red Foxes: Results From Telemetry and Computer Simulation.” In M. W. Fox, ed., The Wild Canids: Their Systematics, Behavioral Ecology, and Evolution, pp. 237-46. New York: Van Nostrand Reinhold. *Wurster-Hill, D. H., K. Benirschke, and D. I. Chapman (1983) “Abnormalities of the X Chromosome in Mammals.” In A. A. Sandberg, ed., Cytogenetics of the Mammalian X Chromosome, Part B, pp. 283–300. New York: Alan R. Liss.

*Zimen, E. (1981) The Wolf: His Place in the Natural World. London: Souvenir Press.

*———(1976) “On the Regulation of Pack Size in Wolves.” Zeitschrift für Tierpsychologie 40:300–341.

Grizzly Bears and Black Bears are largely solitary animals. Some Grizzly populations, however, tend to aggregate around abundant food sources such as salmon, marine mammals (stranded onshore), garbage dumps, and even insect swarms; fairly complex social interactions may develop in these contexts. The heterosexual mating system is polygamous, as both males and females generally mate with multiple partners; males do not contribute to parenting.

Behavioral Expression: Female Grizzly Bears sometimes bond with each other and raise their young together as a single family unit. The two mothers become inseparable companions, traveling and feeding together throughout the summer and fall seasons as they share in the parenting of their cubs. Female companions have not been observed interacting sexually with one another, however. A bonded pair jointly defends their food (such as Elk or Bison carcasses), and the two females also protect one another and their offspring (including defending them against attacks by Grizzly males). The cubs regard both females as their parents, following and responding to either mother equally; bonded females occasionally also nurse each other’s cubs. If one female dies, her companion usually adopts her cubs and looks after them along with her own.

As winter approaches and Grizzlies prepare for hibernation, female coparents often continue to associate with one another. Foraging together late into the fall, they are apparently reluctant to end their relationship and may even delay the onset of their own sleep. Although paired females do not hibernate together, they frequently visit each other (with their cubs) prior to hibernation, staying nearby while their partner prepares her den. They also sleep together outside their denning sites during this final preparatory period and only retreat to their separate dens once the snow gets too deep. Most Grizzlies seek solitude prior to hibernating and locate their winter dens miles away from each other (and with rugged terrain separating them), but bonded females often hibernate relatively close to one another. Such females have even been known to abandon their traditional denning locations to be nearer to their coparent. One female, for example, moved her usual den site more than 14 miles to be closer to her companion. Pair-bonds are not usually resumed after hibernation, although one female may adopt her companion’s yearling offspring the following season. The average age of a bonded female is about 11 years, although Grizzlies as young as 5 and as old as 19 have formed bonds with other females. Companions may be of the same age, or one female might be several years older than the other. Sometimes more than two females are involved: three Grizzlies may form a strongly bonded “triumvirate,” and groups of four or five females have even been known to associate (sometimes also forming pair- or trio-bonds within such a group).

Younger male Black Bears (adolescents and cubs) sometimes mount their siblings, both male and female. One male approaches another with his ears in a CRESCENT configuration (facing forward and perpendicular from the head), then rears up on his hind legs in a STANDING OVER position, in which he places his front paws on the other male’s back. This develops into sexual mounting as he clasps his partner and gently bites the loose skin on his shoulder, sometimes making pelvic thrusts. The other male often rolls over and begins play-fighting with the mounting male, pawing and biting at him.

Intersexual or hermaphrodite Black and Grizzly Bears occur in some populations. These individuals are genetically female and have female internal reproductive organs, combined with various degrees of external male genitalia. In some cases, they have a penislike organ (complete with a penis bone or BACULUM) that is not connected to the internal reproductive organs, while in others the penis is more fully developed, serving as both a genital orifice connected to the womb as well as a urinary organ. Most transgendered Bears are mothers, mating with males and bearing offspring. Some individuals actually copulate and give birth through their “penis”: their male partner inserts his organ into the tip of the intersexual Bear’s phallus, and the resulting offspring emerge through the penis as well.

Frequency: Female bonding and coparenting among Grizzly Bears occur sporadically. In a 12-year study of one population, for example, bonds between females were observed during 4 of those years (a third of the study period), with roughly 20 percent of all females participating in same-sex bonding and coparenting at some point in their life (usually 1–2 years out of an adult life span of 7–12 years). About 9 percent of all Grizzly cubs are raised in families headed by two (or more) pair-bonded mothers (constituting about 4 percent of all families). Sexual activity between younger male Black Bears occurs only occasionally, comprising perhaps less than 2 percent of their play. The incidence of intersexual Bears is probably sporadic as well, although some populations appear to have fairly high proportions: in Alberta, for example, researchers found that 4 out of 38 Black Bears (11 percent) and 1 of 4 Grizzlies were transgendered.

Orientation: Extended heterosexual pair-bonding and parenting by male-female couples do not occur among Grizzly Bears; however, only a subset of females bond with each other and coparent their young. Thus, some individuals are probably more inclined to form same-sex attachments than others, and these females may even develop same-sex bonds on more than one occasion. Although such females mate with males (and may not bond with females in other years), their primary social relationship during the time they are bonded is with their female companion (and their young). Male Black Bears participate in homosexual mounting only as youngsters and adolescents; most probably go on to mate heterosexually as adults.

Some Grizzly and Black Bear populations have significant numbers of nonbreeding animals. Each year, perhaps as many as one-third to one-half of all female Grizzlies do not mate or are otherwise nonreproductive (including copulating with males without becoming pregnant), and some individuals do not breed during their whole lives. In some Black Bear populations, only 16–50 percent of the adult females reproduce each year, and many skip breeding for several years. Female Bears who do become pregnant exhibit DELAYED IMPLANTATION—the fertilized embryo ceases development for about five months before implanting in the uterus. In some cases embryos are reabsorbed, aborted, or prevented from implanting rather than carried to term (e.g., when food supplies are inadequate). In addition, many female Grizzlies and Black Bears delay reproducing anywhere from one to four years after they become sexually mature. Juvenile (sexually immature) Black and Grizzly Bears also engage in sexual activity with each other, including mounting and licking of the vulva. Among adult male Grizzly Bears, higher-ranking individuals often have lower copulation rates because of their preoccupation with aggressive interactions, and in some populations top-ranked males may actually go entire breeding seasons without mating at all. When mating does take place, one partner may display indifference or refusal, and as many as 47 percent of all copulations are incomplete in that they do not involve full penetration or ejaculation. Occasionally, a particularly aggressive male will force a female to mate with him, although females usually have control of the interaction. In fact, females often mate with multiple partners—as many as eight males in a single breeding season for Grizzlies, four to six for Black Bears—and cubs belonging to the same litter may be fathered by different males. Nevertheless, male Black and Grizzly Bears can become violent toward females and cubs, occasionally even killing and cannibalizing adults and/or young. Female Black Bears also sometimes kill cubs that are not their own (especially during the nursing period), although it is not uncommon for mothers of both species to adopt cubs that have been orphaned or abandoned.

Intersexual or transgendered individuals also occur among Polar Bears (Ursus maritimus), comprising about 2 percent of some populations.

*asterisked references discuss homosexuality/transgender

Alt, G. L. (1984) “Cub Adoption in the Black Bear.” Journal of Mammalogy 65:511-12.

Brown, G. (1993) The Great Bear Almanac. New York: Lyons and Beuford.

*Cattet, M. (1988) “Abnormal Sexual Differentiation in Black Bears (Ursus americanus) and Brown Bears (Ursus arctos).” Journal of Mammalogy 69:849–52.

*Craighead, F. C., Jr. (1979) Track of the Grizzly. San Francisco: Sierra Club Books. *Craighead, F. C., Jr., and J. J. Craighead (1972) “Grizzly Bear Prehibernation and Denning Activities as Determined by Radiotracking.” Wildlife Monographs 32:1–35

*Craighead, J. J., J. S. Sumner, and J. A. Mitchell (1995) The Grizzly Bears of Yellowstone: Their Ecology in the Yellowstone Ecosystem, 1959–1992. Washington, D.C. and Covelo, Calif.: Island Press.

*Craighead, J. J., M. G. Hornocker, and F. C. Craighead Jr. (1969) “Reproductive Biology of Young Female Grizzly Bears.” Journal of Reproduction and Fertility, suppl. 6:447–75.

Egbert, A. L. (1978) “The Social Behavior of Brown Bears at McNeil River, Alaska.” Ph.D. thesis, Utah State University.

Egbert, A. L., and A. W. Stokes (1976) “The Social Behavior of Brown Bears on an Alaskan Salmon Stream.” In M. R. Pelton, J. W. Lentfer, and G. E. Folk, eds., Bears—Their Biology and Management: Papers from the Third International Conference on Bear Research and Management, pp. 41–56. Morges, Switzerland: International Union for Conservation of Nature and Natural Resources.

Erickson, A. W., and L. H. Miller (1963) “Cub Adoption in the Brown Bear.” Journal of Mammalogy 44:584–85.

Goodrich, J. M., and S. J. Stiver (1989) “Co-occupancy of a Den by a Pair of Great Basin Black Bears.” Great Basin Naturalist 4:390–91.

*Henry, J. D., and S. M. Herrero (1974) “Social Play in the American Black Bear: Its Similarity to Canid Social Play and an Examination of Its Identifying Characteristics.” American Zoologist 14:371–89.

Jonkel, C. J., and I. McT. Cowan (1971) “The Black Bear in the Spruce-Fir Forest.” Wildlife Monographs 27:1–57.

Rogers, L. (1976) “Effects of Mast and Berry Crop Failures on Survival, Growth, and Reproductive Success of Black Bears.” Transactions of the North American Wildlife and Natural Resources Conference 41:431–38.

Schenk, A., and K. M. Kovacs (1995) “Multiple Mating Between Black Bears Revealed by DNA Fingerprinting.” Animal Behavior 50:1483–90.

Stonorov, D., and A. W. Stokes (1972) “Social Behavior of the Alaska Brown Bear.” In S. Herrero, ed., Bears—Their Biology and Management: Papers from the Second International Conference on Bear Research and Management, pp. 232-42. Morges, Switzerland: International Union for Conservation of Nature and Natural Resources.

Tait, D. E. N. (1980) “Abandonment as a Reproductive Tactic—the Example of Grizzly Bears.” American Naturalist 115:800–808.

Wimsatt, W. A. (1969) “Delayed Implantation in the Ursidae, with Particular Reference to the Black Bear (Ursus americanus Pallus).” In A. C. Enders, ed., Delayed Implantation, pp. 49–76. Chicago: University of Chicago Press.

Spotted Hyenas live in matrilineal clans of 30–80 individuals. Females are dominant to males and remain in their home group for life, while males emigrate to single-sex groups during adolescence and then join other clans (usually for only a few years at a time) on reaching adulthood. This species has a highly organized social system, engaging in cooperative hunting and communal denning. The breeding system is polygynous: generally only one male in each clan mates with several females. Spotted Hyenas are largely nocturnal.

Behavioral Expression: Female Spotted Hyenas have an extraordinary genital configuration that makes them superficially resemble males: the clitoris is 90 percent of the length of the male’s penis (nearly seven inches long) and equal to it in diameter; it can be fully erected. In addition, the labia are fused to resemble a “scrotum” containing fat and connective tissue that give the appearance of testes. There is no vaginal opening—instead, the female mates and gives birth (as well as urinates) through the tip of her clitoris. Heterosexual mating is accomplished by retracting the clitoris inside the abdomen, essentially turning it inside out to form a passageway within which the male can insert his penis. Homosexual mounting between females also occurs in this species; in some cases, an adolescent or younger adult mounts an older one. During a homosexual encounter, one female approaches another with her clitoris erect, often “flipping” it up against her abdomen as a sign of sexual arousal (also seen in males preparing to mate). She may lick her partner on the back, then mount by rising up and clasping her front paws around the other female, resting her head on the other’s neck, and thrusting against her. Clitoral penetration may also occur, though it is not common. Sometimes the female being mounted appears to be disinterested or nonchalant and may even wander off during mounting. These are also characteristics of heterosexual courtship and copulation—females often walk away or do not permit males to achieve penetration and, indeed, may be overtly aggressive toward them. Spotted Hyenas also perform a MEETING CEREMONY involving clitoral erection and genital licking: two females stand parallel to each other but with their heads in opposite directions so that they can access each other’s genitals. One or both of them lifts up her hind leg and allows the other to sniff, nuzzle, and lick her erect clitoris and “scrotum”—sometimes for as long as half a minute at a time—occasionally accompanied by a soft groaning or whining sound. Although meeting ceremonies are sometimes performed between males and females (or between two males), they are most common between females.

Frequency: All adult female Spotted Hyenas have enlarged clitorides and labial “scrota.” Homosexual mounting probably occurs only occasionally in this species, although the majority of meeting ceremonies—anywhere from 55–95 percent—occur between adult females.

Orientation: Most females who participate in same-sex mounting and meeting ceremonies are probably functionally bisexual (if not predominantly heterosexual), also mating with males.

The female Spotted Hyena’s reproductive anatomy and genitals are not optimal for breeding. Heterosexual mating is often difficult, as males have trouble locating and penetrating the clitoral opening. In addition, many females (and infants) suffer severe trauma and even death during the birth process. Because there is no vaginal canal, Hyenas must give birth through the clitoris itself—an extraordinarily painful process, considering that the newborn’s head is significantly larger than the diameter of the clitoris. This causes the clitoral head to rupture in all females during their first birth, and it is estimated that about 9 percent of females in the wild die during their first labor. In addition, the newborn must travel an extraordinarily long way through the female’s birth canal, which makes a 180-degree turn to exit through the clitoris. Because the umbilical cord is less than a third of the length of the birth canal, many babies suffocate during birth—perhaps as many as 60 percent of infants are stillborn to first-time mothers, and a female’s lifetime production of offspring may be reduced by as much as 25 percent because of such complications. Once born, up to a quarter of Spotted Hyena youngsters may be killed by their siblings, who are fiercely competitive and aggressive toward one another. Infanticide (usually by females) also occasionally occurs among Spotted Hyenas, and cannibalism has been reported as well. Most males do not breed at all: the social system of Spotted Hyenas is such that only one male in a clan gets to mate with the females (although other males may participate in heterosexual courtship). Some males, unable to copulate, engage in a form of “masturbation” in which they thrust their penis in the air and spontaneously ejaculate; others have been seen mounting cubs.

Homosexual mounting occurs in Dwarf Mongooses (Helogale undulata), a weasel-like carnivore of Africa. In one group studied in captivity, 16 percent of mounting took place between animals of the same sex (mostly males, including brothers), and some individuals had preferred partners with whom they interacted most frequently. Homosexual behavior has also been observed in two other species of small carnivores: male Common Raccoons (Procyon lotor) and female Martens (Martes sp.).

*asterisked references discuss homosexuality/transgender

*Burr, C. (1996) A Separate Creation: The Search for the Biological Origins of Sexual Orientation. New York: Hyperion.

*East, M. L., H. Hofer, and W. Wickler (1993) “The Erect ‘Penis’ Is a Flag of Submission in a Female-Dominated Society: Greetings in Serengeti Spotted Hyenas.” Behavioral Ecology and Sociobiology 33:355–70.

*Frank, L. G. (1996) “Female Masculinization in the Spotted Hyena: Endocrinology, Behavioral Ecology, and Evolution.” In J. L. Gittleman, ed., Carnivore Behavior, Ecology, and Evolution, vol. 2, pp. 78–131. Ithaca: Cornell University Press.

———(1986) “Social Organization of the Spotted Hyena (Crocuta crocuta). I. Demography. II. Dominance and Reproduction.” Animal Behavior 34:1500–1527.

Frank, L. G., J. M. Davidson, and E. R. Smith (1985) “Androgen Levels in the Spotted Hyena Crocuta crocuta: The Influence of Social Factors.” Journal of Zoology, London 206:525–31.

Frank, L. G., and S. E. Glickman (1994) “Giving Birth Through a Penile Clitoris: Parturition and Dystocia in the Spotted Hyena (Crocuta crocuta).” Journal of Zoology, London 234:659-90.

Frank, L. G., S. E. Glickman, and P. Licht (1991) “Fatal Sibling Aggression, Precocial Development, and Androgens in Neonatal Spotted Hyenas.” Science 252:702-04.

*Frank, L. G., S. E. Glickman, and I. Powch (1990) “Sexual Dimorphism in the Spotted Hyena (Crocuta crocuta ).” Journal of Zoology, London 221:308-13.

*Frank, L. G., M. L. Weldele, and S. E. Glickman (1995) “Masculinization Costs in Hyenas.” Nature 377:584–85.

*Glickman, S. E., C. M. Drea, M. Weldele, L. G. Frank, G. Cunha, and P. Licht (1995) “Sexual Differentiation of the Female Spotted Hyena (Crocuta crocuta).” Paper presented at the 24^th International Ethological Conference, Honolulu, Hawaii.

*Glickman, S. E., L. G. Frank, K. E. Holekamp, L. Smale, and P. Licht (1993) “Costs and Benefits of ‘Andro-genization’ in the Female Spotted Hyena: The Natural Selection of Physiological Mechanisms.” In P. P. G. Bateson, N. Thompson, and P. Klopfer, eds., Perspectives in Ethology, vol. 10: Behavior and Evolution, pp. 87–117. New York: Plenum Press.

*Hamilton, W. H., III, R. L. Tilson, and L.G. Frank (1986) “Sexual Monomorphism in Spotted Hyenas (Crocuta crocuta).” Ethology 71:63–73.

*Harrison Mathews, L. (1939) “Reproduction in the Spotted Hyena, Crocuta crocuta (Erxleben).” Philosophical Transactions of the Royal Society of London, Series B 230:1-78.

*Hofer, H., and M. L. East (1995) “Virilized Sexual Genitalia as Adaptations of Female Spotted Hyenas.” Revue Suisse de Zoologie 102:895–906.

*Kinsey, A. C., W. B. Pomeroy, C. E. Martin, and P. H. Gebhard (1953) Sexual Behavior in the Human Female. Philadelphia: W. B. Saunders.

Kruuk, H. (1975) Hyena. Oxford: Oxford University Press.

———(1972) The Spotted Hyena, a Study of Predation and Social Behavior. Chicago: University of Chicago Press.

*Mills, M. G. L. (1990) Kalahari Hyenas: Comparative Behavioral Ecology of Two Species. London: Unwin Hyman.

*Neaves, W. B., J. E. Griffin, and J. D. Wilson (1980) “Sexual Dimorphism of the Phallus in Spotted Hyena (Crocuta crocuta).” Journal of Reproduction and Fertility 59:509–13.

*Rasa, O. A. E. (1979a) “The Ethology and Sociology of the Dwarf Mongoose (Helogale undulata rufula).” Zeitschrift für Tierpsychologie 43:337-406.

*———(1979b) “The Effects of Crowding on the Social Relationships and Behavior of the Dwarf Mongoose (Helogale undulata rufula).” Zeitschrift für Tierpsychologie 49:317-29.

MARSUPIALS

Eastern Gray Kangaroos often associate in large groups of 40–50 animals—sometimes known as MOBS. These comprise smaller cosexual groups of up to 15 individuals, largely females and their young along with a few males. Some individuals are solitary. No pair-bonding occurs between males and females, and the mating system is polygamous or promiscuous. Whiptail Wallabies have a similar social organization, while Red-necked Wallabies are largely solitary (although groups of 8–30 animals may form at times).

Behavioral Expression: Pair-bonds occasionally develop between female Eastern Gray Kangaroos, involving frequent mutual grooming in which the partners affectionately lick, nibble, and rake the fur on each other’s head and neck with their paws. Females in such associations also sometimes court and mount each other, and sexual activity may occur as well between females who are not necessarily bonded to one another. Significantly, heterosexual pair-bonds are not found in this species. In Red-necked Wallabies, females frequently mount each other: one female grabs the other from behind, wrapping her forearms around her partner’s abdomen and tucking her forepaws inside her partner’s thighs. This position resembles heterosexual copulation except that the mounting female is higher up on her partner’s body. Sexual activity is often accompanied by grooming, fur-nibbling and licking, pawing, and nosing of the partner. Males also sometimes mount one another, usually during play-fights in which the partners gently push, wrestle, or “box” one another with their forearms. Occasional affectionate activities such as grooming, licking, embracing, and touching also take place during these sessions, and sometimes one male will sniff or nuzzle the other’s scrotum. Courtship and sexual interactions between male Whiptail Wallabies involve TAIL-LASHING, a sinuous, sideways movement of the tail indicating sexual arousal, often accompanied by an erection. Mounting also occurs; one male sometimes presents his hindquarters to the other by crouching with his chest on the ground and raising his rump. Prior to mounting, a male frequently sniffs the other male’s scrotum (as in Red-necked Wallabies). Swept up in a courtship frenzy, males also sometimes embark on homosexual chases as a part of heterosexual interactions. A group of males will be pursuing a female in heat, furiously circling and dashing after her at breakneck speed; occasionally, other males on the sidelines are then drawn into the excitement of these wild chases—and they are as likely to pursue other males as they are the female.

In Eastern Gray Kangaroos, intersexual or hermaphrodite individuals also occur: some animals, for example, have both a penis and a pouch (the latter usually found only in females), mammary glands, and testes, all combined with body proportions that are generally intermediate between male and female. Chromosomally, these individuals have a mosaic of the female type (XX), the male type (XY), and a combined XXY pattern.

Frequency: Female homosexual mounting in Eastern Gray Kangaroos occurs sporadically: in one study of a wild population, for example, homosexual behavior was recorded eight times during four months of observation. It should be noted, however, that heterosexual mating is rarely observed as well: only one male-female mating was seen during that same time, while only three heterosexual copulations were recorded during a three-year study of Red-necked Wallabies. In captivity, mounting between female Red-necked Wallabies is quite common, but male homosexual activity is much less frequent. During play-fights between males, courtship and sexual behaviors occur roughly once every five hours of activity. Homosexual mounts between males account for about 1 percent of all mounting activity in Whiptail Wallabies.

Orientation: In captive groups of Eastern Gray Kangaroos (which included both sexes), four of six females formed same-sex pairs. Male Red-necked Wallabies may be sequentially bisexual during their lifetimes: sexual interactions during play-fighting are most common among adolescent males, while adults are probably more heterosexually oriented. Male Whiptail Wallabies that court or mount other males also interact sexually with females, i.e., they are simultaneously bisexual.

Female Red-necked Wallabies are often harassed by males trying to mate with them (similar behavior also occurs in Whiptail Wallabies). As many as seven males at a time may pursue a single female, and they may injure her while mating: females have been seen limping or with cuts on their backs after heterosexual copulations. Mating attempts may also be interrupted by other males charging the pair and trying to dislodge the mounting male. In this species, only about 18 percent of the males ever mate with females. Nonbreeding females also occur in Eastern Gray Kangaroos. In addition, females who are pregnant (including late-term), not in heat, or sexually immature also occasionally participate in heterosexual activity, and males also regularly masturbate by thrusting the erect penis into the paws. DELAYED IMPLANTATION is another notable feature of the reproductive cycle in these species.

Homosexual mounting occurs in a number of other Kangaroo and Wallaby species: between females in Yellow-footed Rock Wallabies (Petrogale xanthopus), and between males in Western Gray Kangaroos (Macropus fuliginosus), Red Kangaroos (Macropus rufus), Agile Wallabies (Macropus agilis), Black-footed Rock Wallabies (Petrogale lateralis), and Swamp Wallabies (Wallabia bicolor). Transgendered or intersexual individuals of various types are also found in several species, including Red Kangaroos, Euros (Macropus robustus), Tammar Wallabies (Macropus eugenii), and Quokkas (Setonix brachyurus). Some of these individuals have female body proportions and external genitalia, female or combined male-female internal reproductive organs, a scrotum, and absence of a pouch and mammary glands. Others have male reproductive organs, intermediate or female body proportions, and a pouch and mammary glands.

*asterisked references discuss homosexuality/transgender

Coulson, G. (1997) “Repertoires of Social Behavior in Captive and Free-Ranging Gray Kangaroos, Macropus giganteus and Macropus fuliginosus (Marsupialia: Macropodidae).” Journal of Zoology, London 242:119–30.

*———(1989) “Repertoires of Social Behavior in the Macropodoidea.” In G. C. Grigg, P. J. Jarman, and I. D. Hume, eds., Kangaroos, Wallabies, and Rat-Kangaroos, pp. 457–73. Chipping Norton, NSW: Surrey Beatty and Sons.

*Grant, T. R., (1974) “Observations of Enclosed and Free-Ranging Gray Kangaroos Macropus giganteus.” Zeitschrift für Säugetierkunde 39:65–78.

*———(1973) “Dominance and Association Among Members of a Captive and a Free-Ranging Group of Gray Kangaroos (Macropus giganteus).” Animal Behavior 21:449–56.

Jarman, P. J., and C. J. Southwell (1986) “Grouping, Association, and Reproductive Strategies in Eastern Gray Kangaroos.” In D. I. Rubenstein and R. W. Wrangham, eds., Ecological Aspects of Social Evolution, pp. 399–428. Princeton: Princeton University Press.

Johnson, C. N. (1989) “Social Interactions and Reproductive Tactics in Red-necked Wallabies (Macropus rufogriseus banksianus).” Journal of Zoology, London 217:267–80.

Kaufmann, J. H. (1975) “Field Observations of the Social Behavior of the Eastern Gray Kangaroo, Macropus giganteus” Animal Behavior 23:214–21.

*———(1974) “Social Ethology of the Whiptail Wallaby, Macropus parryi, in Northeastern New South Wales.” Animal Behavior 22:281–369.

*LaFollette, R. M. (1971) “Agonistic Behavior and Dominance in Confined Wallabies, Wallabia rufogrisea frutica.” Animal Behavior 19:93–101.

Poole, W. E. (1982) “Macropus giganteus Shaw 1790, Eastern Gray Kangaroo.” Mammalian Species 187:1–8.

———(1973) “A Study of Breeding in Gray Kangaroos, Macropus giganteus Shaw and M. fuliginosus (Desmarest), in Central New South Wales.” Australian Journal of Zoology 21:183–212.

Poole, W. E., and P. C. Catling (1974) “Reproduction in the Two Species of Gray Kangaroos, Macropus giganteus Shaw and M. fuliginosus (Desmarest). I. Sexual Maturity and Oestrus.” Australian Journal of Zoology 22:277–302.

*Sharman, G. B., R. L. Hughes, and D. W. Cooper (1990) “The Chromosomal Basis of Sex Differentiation in Marsupials.” Australian Journal of Zoology 37:451–66.

*Stirrat, S. C., and M. Fuller (1997) “The Repertoire of Social Behaviors of Agile Wallabies, Macropus agilis.” Australian Mammalogy 20:71–78.

*Watson, D. M., and D. B. Croft (1993) “Playfighting in Captive Red-Necked Wallabies, Macropus rufogriseus banksianus.” Behavior 126:219–245.

Tree Kangaroos and Rufous Bettongs are largely solitary, although they sometimes associate in pairs, trios, or small groups of adults and young. About 15 percent of Bettong groups are same-sex. The mating systems of these species, though poorly understood, may involve polygamy or promiscuity, perhaps combined with monogamous pair-bonding in some populations of Rufous Bettongs. Males do not generally participate in raising their own offspring.

Behavioral Expression: Female Rufous Bettongs sometimes court and mount other females, using behavior patterns also found in opposite-sex contexts. A homosexual interaction begins with one female approaching another and then sniffing and nuzzling her genital and pouch openings as well as her anus. The courting female becomes sexually aroused and exhibits a sinuous TAIL-LASHING, in which she moves her tail rapidly from side to side. The other female may initially react with hostility (as do females in heterosexual courtships), lying on her side and kicking with her hind feet while softly growling. As a result, the courting female might perform FOOT-DRUMMING, in which she stands upright on her hind legs near the other female and stamps one foot on the ground in front of her. If the other female calms down, the courting female may mount her by clasping her waist from behind and thrusting against her. Some homosexual interactions in Rufous Bettongs involve adult females courting and mounting juvenile females and vice versa. Sometimes males in the vicinity try to intervene or disrupt females engaging in homosexual behavior, but in other cases they simply ignore the activity. Mountings between females, including pelvic thrusting, also occur in Doria’s and Matschie’s Tree Kangaroos.

Frequency: Homosexual interactions occur fairly frequently in captive Rufous Bettongs: in one study, 3 out of 8 mounts were between females, and homosexual activity was observed a total of 19 times over one month. In Tree Kangaroos same-sex mounting occurs only occasionally.

Orientation: Female Rufous Bettongs that participate in homosexual behavior are probably bisexual, since most mate with males and become successful mothers. Most female Tree Kangaroos that mount other females probably also participate in heterosexual activity, although at least one Matschie’s Tree Kangaroo that participated in same-sex mounts was a nonbreeder.

Heterosexual interactions in Rufous Bettongs have a number of nonprocreative aspects. For example, adult males generally make more sexual approaches to juvenile females than to sexually mature adult females. Nonreproductive REVERSE mounts—in which females mount males—occasionally occur in this species, as do attempted mounts by males on females who are not in heat. In the latter case, the female typically responds aggressively, vigorously kicking and growling at him. Although most heterosexual interactions occur between pairs of animals, sometimes two female Rufous Bettongs consort simultaneously with the same male as part of a trio. Among Matschie’s Tree Kangaroos, a form of infanticide known as POUCH-ROBBING has occasionally been observed in captivity, in which females are severely aggressive toward other infants and may actually pull joeys from their mother’s pouch and kill them.

Female Tasmanian Rat Kangaroos (Bettongia gaimardi) also engage in homosexual mounting.

*asterisked references discuss homosexuality/transgender

*Coulson, G. (1989) “Repertoires of Social Behavior in the Macropodoidea.” In G. C. Grigg, P. J. Jarman, and I. D. Hume, eds., Kangaroos, Wallabies, and Rat-Kangaroos, pp. 457–73. Chipping Norton, NSW: Surrey Beatty and Sons.

Dabek, L. (1994) “Reproductive Biology and Behavior of Captive Female Matschie’s Tree Kangaroos, Dendrolagus matschiei.” Ph.D. thesis, University of Washington.

Frederick, H., and C. N. Johnson (1996) “Social Organization in the Rufous Bettong, Aepyprymnus rufescens.” Australian Journal of Zoology 44:9–17.

Ganslosser, U. (1993) “Stages in Formation of Social Relationships—an Experimental Investigation in Kangaroos (Macropodoidea: Mammalia).” Ethology 94:221-47.

*———(1979) “Soziale Kommunikation, Gruppenleben, Spiel- und Jugendverhalten des Doria-Baumkanguruhs (Dendrolagus dorianus Ramsay, 1833) [Social Communication, Group Life, and Play Behavior of Doria’s Tree Kangaroo].” Zeitschrift für Säugetierkunde 44:137–53.

*Ganslosser, U., and C. Fuchs (1988) “Some Quantitative Data on Social Behavior of Rufous Rat-Kangaroos (Aepyprymnus rufescens Gray, 1837 (Mammalia: Potoroidae)) in Captivity.” Zoologischer Anzeiger 220:300–312.

George, G. G. (1977) “Up a Tree with Kangaroos.” Animal Kingdom 80(2):20–24.

*Hutchins, M., G. M. Smith, D. C. Mead, S. Elbin, and J. Steenberg (1991) “Social Behavior of Matschie’s Tree Kangaroo (Dendrolagus matschiei) and Its Implications for Captive Management.” Zoo Biology 10:147–64.

Jarman, P. J. (1991) “Social Behavior and Organization in the Macropodoidea.” Advances in the Study of Behavior 20:1–50.

*Johnson, P. M. (1980) “Observations of the Behavior of the Rufous Rat-Kangaroo, Aepyprymnus rufescens (Gray), in Captivity.” Australian Wildlife Research 7:347–57.

Koalas are largely nocturnal and solitary, although in some populations they tend to live in scattered clusters of two to six females with several males. The mating system is probably promiscuous or polygamous (animals mate with multiple partners), and males take no part in raising their young.

Behavioral Expression: Female Koalas in heat sometimes mount each other in the trees: while one female clings vertically to the trunk, another climbs behind her and reaches around to simultaneously hold on to the tree. She begins to make pelvic thrusts against the other female, while also typically gripping the other female’s neck in her teeth (as does the male during heterosexual mounting). Occasionally one female mounts another from the side (a position sometimes also used by younger males). Usually the mounted female does not display the receptive posture (which involves arching her back while throwing her head back), and homosexual mounts are generally briefer than heterosexual ones. Like male-female copulations, homosexual interactions sometimes involve aggression between the participants: one female may attack the other or pin her to the ground following a mounting. Sometimes two females take turns mounting each other, and homosexual mounting is often interspersed with other signs of intense sexual arousal, including chasing, bellowing, and jerking. BELLOWING is an extraordinary call (also made by males) that has been described as a combination of rasping, growling, wheezing, grunting, rumbling, and braying. It consists of a long series of in-drawn, snorelike breaths alternating with exhalated, belchlike sounds. JERKING is a display resembling the hiccups, in which the female simultaneously jerks her body upward and flicks her head backward repeatedly. Male Koalas also sometimes mount each other, and a few even perform the jerking display like females in heat.

Frequency: In captivity, same-sex mounting accounts for 11 percent of all copulatory activity, with the majority of this being mounts between females.

Orientation: Koalas that participate in homosexual mounting are probably bisexual, since females that mount other females have also been observed mating with males.

Heterosexual relations in Koalas are marked by a striking amount of aggression and violence: more than two-thirds of fights are between males and females rather than between males. Females are sometimes “pestered” by males that persistently follow, touch, bite, or snap at them; if the female returns the bites, the encounter can escalate into a severe fight. Males have been known to brutally attack females—including pregnant and nursing mothers—knocking them from the trees and savagely mauling them. In fact, it is typical for males to nip females on the neck during mating, and for heterosexual copulations to end with the male attacking the female. Females also fight with males (though less violently), and aggressiveness toward males is considered to be a defining feature of estrus for female Koalas. Occasionally adults are also abusive toward babies: mothers sometimes bite their young, while males have been observed attacking infants that interrupt them during a mating with their mother. Many heterosexual interactions are nonprocreative, since males often try to mount females who are not in heat. Although the females typically rebuff their advances, in some cases the males are able to mount them, often thrusting against the female and ejaculating on her without any penetration. Females in heat also sometimes mount males (REVERSE mounts).

Many wild populations of Koalas have particularly high rates of female infertility (and significantly reduced reproductive rates) due to venereal disease. More than half of all females in some areas are infected with genital chlamydia, a bacteria that causes a number of reproductive tract diseases and, ultimately, sterility. This pathogen has apparently been present in Koala populations for a relatively long time, as records of the associated diseases date back to at least the 1890s. Although the exact mode of its transmission is not yet fully understood, two routes have been implicated: sexual and mother-to-young. The latter may be due to the infant Koala’s habit of eating its mother’s feces directly from her anus during weaning, since she produces a special form of excrement known as PAP especially for feeding her young (this practice is also found in a number of other marsupials).

In another marsupial, the Common Brushtail Possum (Trichosurus vulpecula), intersexuality or hermaphroditism occasionally occurs: one individual, for example, had male body proportions, coloring, and genitals combined with mammary glands and a pouch.

*asterisked references discuss homosexuality/transgender

Brown, A. S., A. A. Girjes, M. F. Lavin, P. Timms, and J. B. Woolcock (1987) “Chlamydial Disease in Koalas.” Australian Veterinary Journal 64:346-50.

*Gilmore, D. P. (1965) “Gynandromorphism in Trichosurus vulpecula.” Australian Journal of Science 28:165.

Lee, A., and R. Martin (1988) The Koala: A Natural History. Kensington, Australia: New South Wales University Press.

Phillips, K. (1994) Koalas: Australia’s Ancient Ones. New York: Macmillan.

*Sharman, G. B., R. L. Hughes, and D. W. Cooper (1990) “The Chromosomal Basis of Sex Differentiation in Marsupials.” Australian Journal of Zoology 37:451–66.

Smith, M. (1980a) “Behavior of the Koala, Phascolarctos cinereus (Goldfuss) in Captivity. III. Vocalizations.” Australian Wildlife Research 7:13–34.

*———(1980b) “Behavior of the Koala, Phascolarctos cinereus (Goldfuss) in Captivity. V. Sexual Behavior.” Australian Wildlife Research 7:41–51.

———(1980c) “Behavior of the Koala, Phascolarctos cinereus (Goldfuss) in Captivity. VI. Aggression.” Australian Wildlife Research 7:177–90.

———(1979) “Behavior of the Koala, Phascolarctos cinereus (Goldfuss) in Captivity. I. Non-Social Behavior.” Australian Wildlife Research 6:117-29.

*Thompson, V. D. (1987) “Parturition and Development in the Queensland Koala Phascolarctos cinereus adustus at San Diego Zoo.” International Zoo Yearbook 26:217–22.

Weigler, B. J., A. A. Girjes, N. A. White, N. D. Kunst, F. N. Carrick, and M. F. Lavin (1988) “Aspects of the Epidemiology of Chlamydia psittaci Infection in a Population of Koalas (Phascolarctos cinereus) in Southeastern Queensland, Australia.” Journal of Wildlife Diseases 24:282–91.

Fat-tailed Dunnarts often live together in small groups or pairs that share nests; these groupings are temporary and may consist of individuals of the same sex (especially outside of the breeding season). Although little is known about the social system of Northern Quolls, it appears that most individuals are largely solitary. Both species are nocturnal.

Behavioral Expression: Homosexual mounting occurs among female, and to a lesser extent male, Northern Quolls. One animal climbs on top of another as in a heterosexual mating, grasping its chest with its front paws, and sometimes even riding on the back of the mounted animal as it walks around. In Fat-tailed Dunnarts, females in heat sometimes mount other females.

Frequency: In captivity, homosexual mounting among Northern Quolls occurs in almost two-thirds of encounters between females and 10 percent of encounters between males, though this may not reflect the frequency of its occurrence in the wild. Same-sex mounting only happens occasionally in female Fat-tailed Dunnarts.

Orientation: It is possible that some individuals in these species engage exclusively in same-sex behavior, while others may be bisexual, but little is known about the life histories of specific individuals. In one study, none of the Northern Quolls that participated in homosexual behavior engaged in heterosexual mounting (although observations were not made during the breeding season), while one female Fat-tailed Dunnart that mounted another female did not breed during a nearly yearlong study.

Reproduction in Northern Quolls is characterized by an extraordinary phenomenon sometimes known as MALE DIE-OFF. In many areas, virtually the entire male population perishes following the breeding season, while females typically survive to breed for another couple of seasons (some variation occurs between geographic locations and years in the proportion of males and females surviving). This complete annihilation of males is also a feature of a number of other carnivorous marsupial social systems and is found to a much lesser extent in Fat-tailed Dunnarts. Although the exact mechanism responsible for male mortality is not fully understood, it is thought to result from a number of stress-induced factors, perhaps directly related to participation in procreation. There is some evidence that nonbreeding males with lower testosterone levels—essentially “lower-ranking” males—have a higher survival rate than males that reproduce. Female Northern Quolls also routinely practice “abortion” or elimination of unborn young. As many as 17 embryos may begin developing in the female’s uterus, but because females typically have no more than 8 nipples in their pouch, most of the embryos and/or newborn young will not survive. In Fat-tailed Dunnarts, breeding females can be noticeably aggressive toward males, attacking them when they attempt to mount; in captivity, females have even been known to kill their mates. In this species, heterosexual copulation can be a remarkably long affair, with the male remaining mounted on the female for hours at a time (sometimes as long as 11 hours); the female may struggle and attempt to escape during such arduous matings. In Northern Quolls, females often have neck and chest wounds inflicted by the male during mating. Adult male Fat-tailed Dunnarts sometimes display sexual interest in juvenile females, and incestuous matings have also been recorded. In addition, females in heat occasionally mount males (REVERSE mountings).

Male Stuart’s Marsupial Mice (Antechinus stuartii) mount individuals of both sexes during the mating period. Transgendered (intersexual) Tasmanian Devils (Sarcophilus harrisii) have also been reported: one individual had female genitalia and internal reproductive organs, combined with a scrotum and a pouch with mammary glands on only one side.

*asterisked references discuss homosexuality/transgender

Begg, R. J. (1981) “The Small Mammals of Little Nourlangie Rock, N.T. III. Ecology of Dasyurus hallucatus, the Northern Quoll (Marsupialia: Dasyuridae).” Australian Wildlife Research 8:73–85.

Croft, D. B. (1982) “Communication in the Dasyuridae (Marsupialia): A Review.” In M. Archer, ed., Carnivorous Marsupials, vol. 1, pp. 291–309. Chipping Norton, Australia: Royal Zoological Society of New South Wales.

*Dempster, E. R. (1995) “The Social Behavior of Captive Northern Quolls, Dasyurus hallucatus.” Australian Mammalogy 18:27-34.

Dickman, C. R., and R. W. Braithwaite (1992) “Postmating Mortality of Males in the Dasyurid Marsupials, Dasyurus and Parantechinus.” Journal of Mammalogy 73:143-47.

*Ewer, R. F. (1968) “A Preliminary Survey of the Behavior in Captivity of the Dasyurid Marsupial, Sminthopsis crassicaudata (Gold).” Zeitschrift für Tierpsychologie 25:319-65.

*Lee, A. K., and A. Cockburn (1985) Evolutionary Ecology of Marsupials. Cambridge: Cambridge University Press.

Morton, S. R. (1978) “An Ecological Study of Sminthopsis crassicaudata (Marsupialia: Dasyuridae). II. Behavior and Social Organization. III. Reproduction and Life History.” Australian Wildlife Research 5:163–211.

Schmitt, L. H., A. J. Bradley, C. M. Kemper, D. J. Kitchener, W. F. Humphreys, and R. A. How (1989) “Ecology and Physiology of the Northern Quoll, Dasyurus hallucatus (Marsupialia, Dasyuridae), at Mitchell Plateau, Kimberley, Western Australia.” Journal of Zoology, London 217:539–58.

*Sharman, G. B., R. L. Hughes, and D. W. Cooper (1990) “The Chromosomal Basis of Sex Differentiation in Marsupials.” Australian Journal of Zoology 37:451–66.

RODENTS, INSECTIVORES, AND BATS

Squirrels are generally not gregarious, especially outside of the breeding season, and Red Squirrels defend individual territories throughout the year. The mating system is promiscuous: males and females mate with multiple partners, and only females raise the offspring. Chipmunks are territorial and live in elaborate underground burrows.

Behavioral Expression: Male and female Red Squirrels participate in homosexual mountings, particularly outside of the breeding season. One animal approaches the other from behind (either on the ground or vertically, as on a tree trunk) and grasps it around the waist. The posture used is the same as for heterosexual mating, with the mounter tucking its paws in front of the haunches of the other animal. The mounter often licks, nibbles, or grooms the fur on its partner’s nape or the sides of its neck, and mounting may also be accompanied by play-fighting (harmless “boxing” or kicking sessions) and soft buzzing or mok-calls. Sometimes three animals of the same sex participate in mounting activities at the same time, either alternating among themselves or else all three mounting each other simultaneously (one behind the other in a row). Unlike heterosexual copulation, mounting may be reciprocal, and the mounted animal is usually a more willing participant (although occasionally it will turn around to bite the mounter). In addition, same-sex mounting does not usually involve penetration or pelvic thrusting and is not usually preceded by a courtship chase. Among Gray Squirrels, a similar type of same-sex mounting (with grooming) occurs primarily among younger animals (sometimes among siblings). The activity is often initiated differently from in Red Squirrels, in that the mounting animal makes a bouncing leap onto its partner before grasping it around the waist. Adult male Least Chipmunks also sometimes mount one another.

Occasionally two female Red Squirrels form a bond with each other that includes sexual and affectionate activities and joint parenting. The two share a den (tree hole), follow one another about, and often touch noses or gently nudge each other’s flanks. They also take turns mounting each other, each female nibbling or stroking her partner’s fur while mounting. The pair may raise a single litter of young together; although the youngsters are probably the biological offspring of only one female, both partners may nurse them. In addition, they cooperate in taking care of the young: one such pair was observed leading their lost baby out of a tree and across a street back to their home den. Notably, heterosexual pairs do not usually form in this species: females typically raise young on their own and are generally very aggressive toward other adults that try to approach them.

Frequency: In Red Squirrels, 18 percent of mounts are homosexual; the majority of these are between males, who may participate in same-sex mounts as often as once every half hour outside the breeding season. This is slightly higher than the rate of heterosexual mounting at the same time of the year. Young Gray Squirrels participate in same-sex mounting at a much higher rate, up to 10 times an hour for some age groups (which is more than three times the rate of heterosexual mounting). Among Least Chipmunks, one male was seen to mount another 20 times over four days. Pair-bonding with joint parenting between female Red Squirrels probably occurs only occasionally, although no systematic study has been conducted to determine its prevalence.

Orientation: Adult Red Squirrels that participate in same-sex mounting are seasonally bisexual: outside of the breeding season they engage in both same-sex and opposite-sex mounting, while during the breeding season they mostly participate in heterosexual matings. Females that pair with each other, however, are involved primarily in same-sex activity for the duration of their association, although one and possibly both are functionally bisexual (since they reproduce). Younger animals tend to mount their siblings and therefore are either simultaneously bisexual (interacting with both males and females) or, among males, primarily homosexual (interacting mostly with other males even if females are present). Gray Squirrels are sequentially or chronologically bisexual: juveniles, adolescents, and young adults (up to one and a half years old) show a preference for homosexual activity, while older adults generally exhibit much less same-sex mounting. Since males do not usually start breeding until they are 18 months old, some individuals may be involved exclusively in homosexuality up to that time.

Both Red and Gray Squirrels participate in a wide range of nonprocreative sexual activities. Heterosexual mounting outside of the breeding periods is common, especially in Red Squirrels. Since males have a seasonal sexual cycle that renders them infertile at these times (like females), this activity is definitely nonreproductive. In addition, penetration is usually not involved, and REVERSE mounting (females mounting males) also occurs, accounting for about 5 percent of such activity in Red Squirrels. Sexual behavior also takes place in other situations that are not optimal for breeding. Juveniles of both species often participate in mounting or sexual chases, for example, including incestuous activity between siblings or mothers being mounted by their offspring. Interspecies mating chases have also been observed between Gray Squirrels and fox squirrels (Sciurus niger).

During Gray Squirrel mating chases, as many as 34 males may pursue and harass a single female; when cornered in a tree cavity or at the end of a limb, she often defends herself by screaming and lunging at the males and then bolting away. Mounts by males result in full copulation only 40 percent of the time, as females usually escape from a male that is trying to mate with them. In addition, mating pairs are often attacked by other males, who knock the couple from the tree or savagely bite them, in some cases inflicting fatal wounds on the female. When mating does occur, the female copulates with several different males, sometimes as many as eight during a single mating bout. Mating chases in Red Squirrels can involve up to seven males at a time; a female may drag a male mounted on her for some distance or vigorously try to shake him off her back. In Gray Squirrels, sperm coagulates in the female’s vagina following copulation, forming a plug that may prevent inseminations by other males. However, females often remove these plugs, thereby preventing insemination by the male who just mated with them (while at the same time possibly allowing subsequent males to impregnate them). Young Red Squirrels sometimes suffer fatal injuries from adults during territory takeovers, and Gray Squirrel youngsters are occasionally attacked and/or cannibalized by adults. Not all adults participate in breeding: about a third of female Red Squirrels in some populations are nonbreeders, while about 30 percent of male Gray Squirrels do not mate with females each breeding season (and some individuals skip entire seasons).

*asterisked references discuss homosexuality/transgender

Barkalow, F. S., Jr., and M. Shorten (1973) The World of the Gray Squirrel. Philadelphia and New York: J.B. Lippincott.

Ferron, J. (1981) “Comparative Ontogeny of Behavior in Four Species of Squirrels (Sciuridae).” Zeitschrift für Tierpsychologie 55:193–216.

*———(1980) “Le comportement cohésif de l’Écureuil roux (Tamiasciurus hudsonicus) [Cohesive Behavior of the Red Squirrel].” Biology of Behavior 5:118–38.

*Horwich, R. H. (1972) The Ontogeny of Social Behavior in the Gray Squirrel (Sciurus carolinensis). Berlin and Hamburg: Paul Parey.

Koprowski, J. L. (1994) “Sciurus carolinensis.” Mammalian Species 480:1–9.

———(1993) “Alternative Reproductive Tactics in Male Eastern Gray Squirrels: ‘Making the Best of a Bad Job.’” Behavioral Ecology 4:165–71.

———(1992a) “Do Estrous Female Gray Squirrels, Sciurus carolinensis, Advertise Their Receptivity?” Canadian Field-Naturalist 106:392–94.

———(1992b) “Removal of Copulatory Plugs by Female Tree Squirrels.” Journal of Mammalogy 73:572–76.

———(1991) “Mixed-species Mating Chases of Fox Squirrels, Sciurus niger, and Eastern Gray Squirrels, S. carolinensis.” Canadian Field-Naturalist 105:117–18.

*Layne, J. C. (1954) “The Biology of the Red Squirrel, Tamiasciurus hudsonicus loquax (Bangs), in Central New York.” Ecological Monographs 24:227–67.

Moore, C. M. (1968) “Sympatric Species of Tree Squirrels Mix in Mating Chase.” Journal of Mammalogy 49:531–33.

Price, K., and S. Boutin (1993) “Territorial Bequeathal by Red Squirrel Mothers.” Behavioral Ecology 4:144–49.

*Reilly, R. E. (1972) “Pseudo-Copulatory Behavior in Eutamias minimus in an Enclosure.” American Midland Naturalist 88:232.

Smith, C. C. (1978) “Structure and Function of the Vocalizations of Tree Squirrels (Tamiasciurus).” Journal of Mammalogy 59:793–808.

*———(1968) “The Adaptive Nature of Social Organization in the Genus of Tree Squirrels Tamiasciurus.” Ecological Monographs 38:31–63.

Thompson, D. C. (1978) “The Social System of the Gray Squirrel.” Behavior 64:305–28.

———(1977) “Reproductive Behavior of the Gray Squirrel.” Canadian Journal of Zoology 55:1176–84.

———(1976) “Accidental Mortality and Cannibalization of a Nestling Gray Squirrel.” Canadian Field-Naturalist 90:52–53.

These two species of Marmots are highly social creatures that live in clusters of colonies; each colony is a series of underground burrows that is home to one male, one to three females, and their offspring. Males are generally not involved directly in parental care of their young. Occasionally an additional SATELLITE male is peripherally associated with an Olympic Marmot colony.

Behavioral Expression: Olympic and Hoary Marmot females often mount other females and participate in other same-sex affectionate and sexual behaviors, especially when they are in heat. A homosexual encounter often begins with a “greeting” interaction in which the two females touch noses or mouths, or one female nuzzles her nose on the other’s cheek or mouth. She may also gently chew on the ear or neck of the other female, who then responds by raising her tail. The first female sometimes also sniffs or nuzzles the other’s genitals with her mouth. At this point she may mount the other female, gently biting her neck fur while she thrusts against her partner. The female being mounted arches her back and holds her tail to the side to facilitate the sexual interaction.

Frequency: Homosexual behavior is quite common in Marmots: in one study of Hoary Marmots, for example, three of five observed mounts by adults were between females.

Orientation: Many female Marmots that participate in same-sex mountings also mate with males. However, some nonbreeding females in Hoary Marmots (see below) probably also participate, which means that they may be involved only in homosexual interactions for those seasons that they do not breed.

Although many Marmots form monogamous heterosexual pair-bonds, in some populations the majority (two-thirds) of Hoary Marmots actually live in trios consisting of one male and two females. Occasionally a “quartet” of one male and three females live together as well. Some male Hoary Marmots also seek promiscuous matings with females outside their colony, a behavior that has been termed GALLIVANTING. A form of reproductive suppression occurs in this species as well: females usually procreate every other year, but 11 percent of the time, a female “skips” breeding for two consecutive years. This is especially common in trios, where the two females alternate their skipping patterns. Males sometimes still try to mount females that are not breeding, however. Sexual activity also occurs among juveniles, including mounting of adults.

*asterisked references discuss homosexuality/transgender

*Barash, D. P. (1989) Marmots: Social Behavior and Ecology. Stanford: Stanford University Press.

———(1981) “Mate Guarding and Gallivanting by Male Hoary Marmots (Marmota caligata).” Behavioral Ecology and Sociobiology 9:187–93.

*———(1974) “The Social Behavior of the Hoary Marmot (Marmota caligata).” Animal Behavior 22:256–61.

*———(1973) “The Social Biology of the Olympic Marmot.” Animal Behavior Monographs 6:171–245.

Holmes, W. G. (1984) “The Ecological Basis of Monogamy in Alaskan Hoary Marmots.” In J. O. Murie and G. R. Michener, eds., The Biology of Ground-Dwelling Squirrels: Annual Cycles, Behavioral Ecology, and Sociality, pp. 250–74. Lincoln: University of Nebraska Press.

Wasser, S. K., and D. P. Barash (1983) “Reproductive Suppression Among Female Mammals: Implications for Biomedicine and Sexual Selection Theory.” Quarterly Review of Biology 58:513–38.

Cavies live in colonies of 20–50 animals, although no permanent social groupings occur. Each female usually has her own home bush under which she lives and raises her young. The mating system is promiscuous, in that males and females copulate with multiple partners without forming any long-lasting heterosexual bonds.

Behavioral Expression: Cavies participate in a wide variety of homosexual courtship patterns, most of which are also found in heterosexual interactions. In Dwarf Cavies, adult males are sexually attracted to juveniles of both sexes. A typical homosexual courtship begins with the adult and the younger male sitting quietly together—often right in front of the youngster’s mother, who is not visibly disturbed. The two males may kiss and nuzzle their noses together, after which the adult begins to gently nibble on the juvenile’s rump. This is often followed by a courtship behavior known as CHIN-RUMP FOLLOWING, in which the adult male places his chin on the youngster’s rump, as they move together in circles or figure-eight patterns. If the male is especially aroused, he will stop to pat his paws against the juvenile’s rump, sometimes even licking, sniffing, and nuzzling the anus and perineal region while lifting up the youngster’s hindquarters with his nose. Adult males frequently have favorite males that they prefer to court and interact sexually with, actively seeking them out while ignoring others.

Female Cuis (and less commonly, males) use a stylized form of same-sex courtship chasing known as REARING: one female approaches another and rears up on her hind legs as if to mount, then drops back down on all fours to follow the other female, repeating the pattern. Sometimes this leads to actual mounting, in which one female thrusts against the other in an upright posture behind her. Homosexual mounting is common when females are in heat, but it also occurs when a female is not in heat and even when she is pregnant. Among Apereas, females court one another by performing the RUMBA: in this courtship dance, one female rhythmically sways her hindquarters from side to side while slowly approaching, circling, or following another female. She may also make a burbling sound known as RUMBLING. Adult male Apereas sometimes court younger males by RUMPING, in which the adult throws one or both hind legs over the rump of the youngster.

Dwarf Cavies also sometimes bond with animals of the same sex, forming “companionships” and even coparenting arrangements. Two (occasionally three) females share a home (living under the same bush), frequently sitting together and kissing each other with prolonged nuzzling of mouths and noses. They may even cooperate in nursing one another’s young. Adult males occasionally also have an adolescent companion; the two males sit and feed together, as well as kiss one another. Sometimes the adult male will permit his companion to mount a female that he is courting.

Frequency: Homosexual courtships make up 58 percent of adult-juvenile chin-rump follows (and 44 percent of all such courtships) in Dwarf Cavies, while more than a third of Cui courtship rearing interactions are between females. Homosexual courtships are less common in Apereas.

Orientation: Most Cavies that participate in same-sex activities are probably bisexual. For example, adult male Apereas and Dwarf Cavies court both juvenile males and females, while same-sex bonded Dwarf Cavies usually copulate with members of the opposite sex. However, there are differences in the apparent preference of adult males for homosexual interactions: in Dwarf Cavies, the majority of adult-juvenile courtships are homosexual, while in Apereas fewer such courtships are same-sex.

Cavies regularly engage in heterosexual courtship and sexual behaviors that are nonprocreative. Female Cuis that are pregnant, lactating, or not in heat, for example, often participate in mounting and courtship (including REVERSE mounting of males). Aperea males commonly court pregnant females. Male Dwarf Cavies occasionally masturbate by sitting back on their haunches, making pelvic thrusts, and then licking and nuzzling the erect penis. As mentioned above, sexual behavior between adults and juveniles is widespread in these species. About a quarter of all courtship and sexual interactions in Dwarf Cavies involve adult males and juveniles, while adult male Cuis also chin-rump follow juvenile females as young as two weeks old. In addition, juvenile Cuis of both sexes sometimes mount both adult males and females, including their own mothers. Cui mothers have also developed an extensive system of communal nursing in which most females suckle young other than their own. Although each female nurses her own offspring for longer periods than she does others’, she may actually spend a greater total amount of time nursing nonoffspring.

Homosexual behavior occurs in several other rodents. Adult males in two other species of Cavies, the Mocó or Rock Cavy (Kerodon rupestris) and the Prea (Galea spixii), also sometimes court juvenile males, and youngsters mount adults of both sexes as well. Male Spinifex Hopping Mice (Notomys alexis) from Australia sometimes engage in sexual and bonding activities with one another, including mounting, nesting together, feeding and resting beside each other, and burrowing in tandem. Both male and female Brown Rats (Rattus norvegicus, the wild ancestor of the common household and laboratory rat) participate in homosexual mounting. Male Eastern Cottontail Rabbits (Sylvilagus floridanus) sometimes court other males in addition to females, including displays such as the JUMP SEQUENCE, in which the two males alternately rush toward and jump over one another. Males in this species also occasionally attempt to mount other males. In some populations of Kangaroo Rats (Dipodomys ordii), as many as 16 percent of the animals are intersexed, having the reproductive organs of both sexes (including a vagina, penis, uterus, and testes).

*asterisked references discuss homosexuality/transgender

*Barnett, S. A. (1958) “An Analysis of Social Behavior in Wild Rats.” Proceedings of the Zoological Society of London 130:107-52.

*Happold, M. (1976) “Social Behavior of the Conilurine Rodents (Muridae) of Australia.” Zeitschrift für Tierpsychologie 40:113–82.

Künkele, J., and H. N. Hoeck (1995) “Communal Suckling in the Cavy Galea musteloides.” Behavioral Ecology and Sociobiology 37:385–91.

*Lacher, T. E., Jr. (1981) “The Comparative Social Behavior of Kerodon rupestris and Galea spixii and the Evolution of Behavior in the Caviidae.” Bulletin of the Carnegie Museum of Natural History 17:1–71.

*Marsden, H. M., and N. R. Holler (1964) “Social Behavior in Confined Populations of the Cottontail and the Swamp Rabbit.” Wildlife Monographs 13:1–39.

*Pfaffenberger, G. S., F. W. Weckerly, and T. L. Best (1986) “Male Pseudohermaphroditism in a Population of Kangaroo Rats, Dipodomys ordii.” Southwestern Naturalist 31:124–26.

*Rood, J. P. (1972) “Ecological and Behavioral Comparisons of Three Genera of Argentine Cavies.” Animal Behavior Monographs 5:1–83.

*———(1970) “Ecology and Social Behavior of the Desert Cavy (Microcavia australis).” American Midland Naturalist 83:415–54.

Stahnke, A., and H. Hendrichs (1990) “Cavy Rodents.” In Grzimek’s Encyclopedia of Mammals, vol. 3, pp. 325-37. New York: McGraw-Hill.

Long-eared Hedgehogs live in burrows and are largely nocturnal and solitary, although small groups of animals may gather at feeding or resting sites. Males take no part in parental care.

Behavioral Expression: Homosexual interactions in female Long-eared Hedgehogs involve a great deal of courtship and affectionate behaviors as well as direct sexual encounters, frequently consisting of oral sex. A typical lesbian interaction begins, often at dusk, with two females rubbing each other, sliding along each other’s body, and cuddling. One female might also crawl directly under the other, sliding back from her throat to her belly. Another courtship display involves one female stretching out full length and pressing her belly against the ground with a concave “arch” in her back. During sexual contact, females intensively lick, sniff, and nibble on each other’s genitals. Sometimes, to have better access, one female will raise the hindquarters of the other high into the air with her paws and lower jaw, lifting her partner’s hind legs clear off the ground while she continues licking. At other times, one or both females will present their raised hindquarters as an invitation for the other to mount as in heterosexual copulation. Often the presenting female is in such a state of arousal that her hindquarters are actually lifted too high for the other female to fully mount her, although she may try. In captivity, homosexual encounters have been observed between adult sisters, that is, members of the same litter.

Frequency: Homosexual interactions occur frequently between females paired together in captivity, but the incidence of this activity in wild Long-eared Hedgehogs is not known.

Orientation: Female Long-eared Hedgehogs may have a latent capacity for bisexual or homosexual behavior, since same-sex activity surfaces when females are kept together without males. However, it appears that this may initiate a preference for homosexuality that can be long-lasting: one pair of females who courted and had sex with each other refused to participate in heterosexual activity for more than two years after they were separated, although eventually both did mate with males and reproduce.

Oral-genital stimulation is a frequent component of heterosexual encounters in Long-eared Hedgehogs, with males licking and sniffing the female’s genitals. Cannibalism also occurs in this species: animals may eat already dead hedgehogs or else kill them directly and then devour them.

Homosexual activity occurs in several species of Tree Shrews, a group of animals found in Southeast Asia and thought to have affiliations with insectivores (and possibly also primates). In Common Tree Shrews (Tupaia glis), for example, about a third of all sexual activity occurs between females, including sexual approaches and following, genital licking and sniffing, and mounting. Same-sex mounting has also been observed in Slender Tree Shrews (T. gracilis), Mountain Tree Shrews (T. montana), and Long-footed Tree Shrews (T. longipes). In the latter species, mounting between females accounts for about 9 percent of all mounting activity. Female Long-footed Tree Shrews sometimes form consortships with one another as well; these typically last longer than heterosexual consortships (several months as opposed to several hours) and involve mutual grooming, lying on or next to each other, and sleeping together. Male and female homosexuality also occur in North American Porcupines (Erethizon dorsatum), including periods of exclusive homosexual activity among males.

*asterisked references discuss homosexuality/transgender

*Kaufmann, J. H. (1965) “Studies on the Behavior of Captive Tree Shrews (Tupaia glis).” Folia Primatologica 3:50–74.

*Kinsey, A. C., W. B. Pomeroy, C. E. Martin, and P. H. Gebhard (1953) Sexual Behavior in the Human Female. Philadelphia: W. B. Saunders.

Maheshwari, U. K. (1984) “Food of the Long Eared Hedgehog in Ravine Near Agra.” Acta Theriologica 29:133–37.

*Poduschka, W. (1981) “Abnormes Sexualverhalten Zusammengehaltener, Weiblicher Hemiechinus auritus syriacus (Insectivora: Erinaceinae) [Abnormal Sexual Behavior of Confined Female Hemiechinus auritus syriacus].” Bijdragen tot de Dierkunde 51:81–88.

Prakash, I. (1953) “Cannibalism in Hedgehogs.” Journal of the Bombay Natural History Society 51:730–31.

Reeve, N. (1994) Hedgehogs. London: T. and A. D. Poyser.

Schoenfeld, M., and Y. Yom-Tov (1985) “The Biology of Two Species of Hedgehogs, Erinaceus europaeus concolor and Hemiechinus auritus aegyptus, in Israel.” Mammalia 49:339–55.

*Sorenson, M.W., and C. H. Conaway (1968) “The Social and Reproductive Behavior of Tupaia montana in Captivity.” Journal of Mammalogy 49:502–12.

*———(1966) “Observations on the Social Behavior of Tree Shrews in Captivity.” Folia Primatologica 4:124–45.

Gray-headed Flying Foxes live in groups known as CAMPS, which may contain many thousands of individuals. These camps are segregated by sex for most of the year: males and females roost in separate trees—or in separate locations within the same tree—except during the breeding season (generally March-April). Some individuals become nomadic, solitary, or much less gregarious following the breeding season. Livingstone’s Fruit Bats appear to have a polygamous mating system, in which males mate with multiple female partners but do not participate in raising their offspring. Vampire Bat colonies may contain up to 2,000 individuals, although most have 20–100. The female group is the primary social unit, consisting of 8–12 females (many of whom are related to each other) and their young. Males sometimes form “bachelor” groups of up to 8 individuals, or they may roost in the same tree with female groups.

Behavioral Expression: Gray-headed Flying Foxes of both sexes engage in a form of mutual homosexual grooming and caressing when they are in their separate camps. One animal wraps its wings around another of the same sex in an embrace, licking and gently biting the chest and wings of its partner, rubbing its head on the other’s chest, and grooming it with its claws. Males may have an erection while they do this, and individuals generally utter a continuous pulsed, grating call while engaged in this activity. Livingstone’s Fruit Bats participate in similar forms of grooming and other homosexual activities. Combined with bouts of intense body licking—either mutual or one-sided—both males and females in this species sometimes lick, nuzzle, and sniff the genitals of a same-sex partner (one male was even seen to drink another’s urine as part of this activity). Clasping, play-wrestling, and gentle mouthing or biting of the partner occur as well. This may lead to homosexual mounting, in which one Bat grips the other from behind, holding the scruff of its neck in its mouth (as in heterosexual mating, although males do not usually experience erections or penetration during same-sex activity). Females sometimes mount their adult daughters and vice versa. In one instance, a daughter repeatedly approached, pursued, and mounted her mother for extended periods, and even successfully fought off males who were interested in mating with her mother.

Male Vampire Bats also participate in sexual grooming and licking of one another. Two males hang belly to belly, each with an erect penis. One male then works his tongue over the entire body of the other male, paying particular attention to licking the other male’s genitals. Sometimes one male will masturbate himself while licking his partner, using his free foot to rub his own penis. Although overt sexual behavior has not been observed among female Vampire Bats, females do form long-lasting bonds with one another. Companions share the same roost, groom one another, huddle together, and go foraging with each other. Another important aspect of these female companionships is blood-sharing: one female feeds the other by “donating” or regurgitating blood for her to consume (males also occasionally engage in reciprocal blood-sharing). Associations like these can last for five to ten years or more, and some females bond with several different female companions simultaneously.

Frequency: Overt sexual behavior among Gray-headed Flying Foxes and Vampire Bats probably occurs only occasionally (and is more common in male Flying Foxes than in females), but various same-sex activities occur regularly in Livingstone’s Fruit Bats (in captivity). In Vampire Bats, between one-half and three-quarters of all companionships or close associations are between females.

Orientation: Little is known of the individual life histories of these Bats, and so it is difficult to draw any definitive conclusions regarding the orientation of their sexual behavior. Nevertheless, it is likely that many Gray-headed Flying Foxes are seasonally bisexual, since they participate in homosexual activities when they are in the sex-segregated camps during the nonbreeding season. Among Vampire Bats in captivity, some males seem to show what amounts to a preference for homosexual activity, since they bypass females in order to interact sexually with another male (although it is not known whether this “preference” is temporary or long-lasting). Livingstone’s Fruit Bats may be simultaneously bisexual, able to alternate between same-sex and opposite-sex activities in a relatively short span of time.

Heterosexuality in all three of these species of Bats is characterized by a variety of nonreproductive sexual behaviors. Gray-headed Flying Foxes copulate throughout the year, including outside the breeding season when females cannot get pregnant, and mating also takes place during pregnancy. In addition, males have a distinct annual hormonal cycle that affects sperm production, with the result that many of their matings are nonprocreative. Male Livingstone’s Fruit Bats sometimes participate in heterosexual mounting without an erection or penetration, and females may REVERSE mount males as well. A prominent feature of Gray-headed Flying Fox sexual behavior is oral sex, in which the male deeply tongues the female’s genitalia for long periods. Both male and female Livingstone’s Fruit Bats also lick the genitals of their partners during heterosexual interactions. In Vampire Bats, masturbation occurs among younger males, while male Livingstone’s Fruit Bats have been observed licking their own penises to erection. Female Vampire Bats sometimes mate with several different males in succession. In this species, a vaginal plug forms in the female’s reproductive tract following copulation, which may prevent insemination from subsequent matings. When not in heat females frequently refuse to mate with males altogether, especially aggressive ones. Heterosexual relations in Livingstone’s Fruit Bats are also less than amicable: females sometimes cuff males or otherwise refuse their advances, and partners may threaten, wrestle, cuff, and bite each other during actual courtship and mating. Vampire Bats have developed an alternative form of parenting behavior in their female groups known as FOOD SHARING: females sometimes help each other feed infants by regurgitating blood for young that are not their own.

Male Serotine Bats (Eptesicus serotinus), a Eurasian species, have been observed making sexual advances toward other males in captivity. While suspended upside down, one male approaches another with his penis erect and mounts him from behind, grasping him above the neck and thrusting his penis between the other male’s legs (under the membrane that stretches between his limbs). Homosexual activity in several species of British Bats is also common among wild males during the spring and summer (i.e., outside of the breeding season). These include Noctules (Nyctalus noctula), Common Pipistrelles (Pipistrellus pipistrellus), Brown Long-eared Bats (Plecotus auritus), Daubenton’s Bats (Myotis daubentonii), and Natterer’s Bats (Myotis nattereri) (including interspecies encounters between the latter two). Among wild Little Brown Bats (Myotis lucifugus) in North America, males often mount other males (as well as females) during the late fall, when many of the mounted individuals are semitorpid. These same-sex copulations usually include ejaculation, and the mounted animal often makes a squawking vocalization. Homosexual behavior also occurs in several other species of Fruit Bats: male Rodrigues Fruit Bats (Pteropus rodricensis) participate in same-sex mounting, while younger male Indian Fruit Bats (Pteropus giganteus) often mount one another (with erections and thrusting) while play-wrestling.

*asterisked references discuss homosexuality/transgender

*Barclay, R. M. R., and D. W. Thomas (1979) “Copulation Call of Myotis lucifugus: A Discrete Situation-Specific Communication Signal.” Journal of Mammalogy 60:632–34.

*Courts, S. E. (1996) “An Ethogram of Captive Livingstone’s Fruit Bats Pteropus livingstonii in a New Enclosure at Jersey Wildlife Preservation Trust.” Dodo 32:15–37.

DeNault, L. K., and D. A. McFarlane (1995) “Reciprocal Altruism Between Male Vampire Bats, Desmodus rotundus.” Animal Behavior 49:855–56.

*Greenhall, A. M. (1965) “Notes on the Behavior of Captive Vampire Bats.” Mammalia 29:441–51.

Martin, L., J. H. Kennedy, L. Little, H. C. Luckhoff, G. M. O’Brien, C. S. T. Pow, P. A. Towers, A. K. Waldon, and D. Y. Wang (1995) “The Reproductive Biology of Australian Flying-Foxes (Genus Pteropus).” In P. A. Racey and S. M. Swift, eds., Ecology, Evolution, and Behavior of Bats, pp. 167–84. Oxford: Clarendon Press.

*Nelson, J. E. (1965) “Behavior of Australian Pteropodidae (Megachiroptera).” Animal Behavior 13:544–57.

*———(1964) “Vocal Communication in Australian Flying Foxes (Pteropodidae; Megachiroptera).” Zeitschrift für Tierpsychologie 21:857–70.

*Neuweiler, V. G. (1969) “Verhaltensbeobachtungen an einer indischen Flughundkolonie (Pteropus g. giganteus Briinn) [Behavioral Observations on a Colony of Indian Fruit-Bats].” Zeitschrift für Tierpsychologie 26:166–99.

*Rollinat, R., and E. Trouessart (1896) “Sur la reproduction des chauves-souris [On the Reproduction of Bats].” Mémoires de la Societe Zoologique de France 9:214-40.

*———(1895) “Deuxième note sur la reproduction des Chiropteres [Second Note on the Reproduction of the Chiroptera].” Comptes Rendus Hebdomadaires des Séances et Mémoires de la Société de Biologie 47:534–36.

Schmidt, C. (1988) “Reproduction.” In A. M. Greenhall and U. Schmidt, eds., Natural History of Vampire Bats, pp. 99–109. Boca Raton, Fla.: CRC Press.

*Thomas, D. W., M. B. Fenton, and R. M. R. Barclay (1979) “Social Behavior of the Little Brown Bat, Myotis lucifugus. I. Mating Behavior. II. Vocal Communication.” Behavioral Ecology and Sociobiology 6:129–46.

Trewhella, W. J., P. F. Reason, J. G. Davies, and S. Wray (1995) “Observations on the Timing of Reproduction in the Congeneric Comoro Island Fruit Bats, Pteropus livingstonii and P. seychellensis comorensis.” Journal of Zoology, London 236:327–31.

Turner, D. C. (1975) The Vampire Bat: A Field Study in Behavior and Ecology. Baltimore: Johns Hopkins University Press.

*Vesey-Fitzgerald, B. (1949) British Bats. London: Methuen.

Wilkinson, G. S. (1988) “Social Organization and Behavior.” In A. M. Greenhall and U. Schmidt, eds., Natural History of Vampire Bats, pp. 85–97. Boca Raton, Fla.: CRC Press.

*———(1985) “The Social Organization of the Common Vampire Bat. I. Pattern and Cause of Association. II. Mating System, Genetic Structure, and Relatedness.” Behavioral Ecology and Sociobiology 17:111–34.

———(1984) “Reciprocal Food Sharing in the Vampire Bat.” Nature 308:181–84.

GEESE, SWANS, AND DUCKS

Greylag Geese usually associate in flocks containing a complex mixture of pairs, families with offspring, single birds, and subgroups of juveniles. Following the breeding season, migratory flocks sometimes contain thousands of birds. The mating system generally involves long-term, monogamous pair-bonding.

Behavioral Expression: Homosexual pairs made up of two ganders are a prominent form of pair-bonding in Greylag Geese. Male couples are stable and long-lasting: some have been documented as persisting for more than fifteen years, and most homosexual pairs (like heterosexual ones) are probably lifelong partnerships (Greylag Geese can live to be more than 20 years old). “Widower” ganders may even exhibit signs of “grief,” becoming despondent and defenseless upon the loss of their male partner. Most heterosexual pairs are also lifelong (and partners grieve the loss of their mates), but in many cases gander pairs are actually more closely bonded than male-female pairs, due in part to the intensity of their displays. One of these is the TRIUMPH CEREMONY, a pair-bonding behavior in which the two partners approach each other with extended necks and spread wings while making loud gabbling calls. Gander pairs spend significantly more time in this activity than do heterosexual pairs. They are also generally more vocal than male-female pairs—they often utter PRESSED CACKLING calls (rapid syllables produced with a high-pressure airstream) together in a cheek-to-cheek position and may even perform extended duets with ROLLING calls (deeper and louder notes).

Paired ganders also sometimes engage in courtship and sexual behavior with one another. Pair-bonding is often initiated with the BENT-NECK DISPLAY, in which one male approaches and follows another with a distinct “kink” in his neck, his bill pointing downward. As a prelude to mating, both males perform aquatic displays such as NECK-DIPPING or NECK-ARCHING, in which the head is dipped below the surface while the neck is held in an elegant curve, its feathers ruffled to reveal their distinctive patterning. Following these displays, one male may mount the other as in heterosexual copulation. If there is a size difference between the two males, often the larger male mounts the smaller one. If the two ganders are equal in size, either bird may mount the other, and they often exchange positions when they copulate on different days. Following mating, the male who mounted his partner performs a display in which he lifts his head up and arches his folded wings almost vertically above his back. Sometimes, during homosexual activity one male may “masturbate” by mounting a log or some other object (a common form of masturbation in birds). In addition, a third bird—either male or female—occasionally joins a homosexual pair in their courtship activities, and may even be mounted by one of the ganders. In all cases, though, the concluding display takes place between the members of the male pair rather than with the third bird. Some gander pairs do not regularly engage in full mounting behavior, in part because both males prefer to mount each other without either one permitting himself to be mounted.

Gander pairs often assume a powerful, high-ranking position within their flock, owing to their superior strength and courage. They are notably more aggressive than heterosexual pairs, frequently threatening, charging, chasing, and jointly attacking predators as well as other geese (especially unpaired males) and often appear to “terrorize” other birds. Paradoxically, each individual gander in a homosexual pair is significantly less aggressive than a male in a heterosexual pair—it is their combined strength that gives the couple its advantage. Homosexual pairs also differ from heterosexual ones in spending significantly more time on the periphery of the flock or away from it, especially during the spring breeding season. This, combined with the gander pair’s greater vigilance behavior (as well as the pair’s aggressiveness), has led some researchers to suggest that homosexual pairs may act as “guardians” for the flock as a whole. Sometimes a female is attracted to a gander pair—perhaps because of their strength and high standing—and tries to establish a bond with one or both of them. Often the males simply ignore such a female, but in some cases she is allowed to join them to form a trio. When this happens, one or both ganders may copulate with the female, although their homosexual bond usually remains primary. The trio may raise a family together, with the two ganders often searching for a nest site together and jointly defending their eggs and goslings. Occasionally, three ganders bond with each other as a same-sex trio, which may also later be joined by a female to form a “quartet”; again, goslings can be raised by all four birds together.

Although most gander pairs are stable partnerships, occasionally one or both birds may behave antagonistically toward his partner. Fights sometimes erupt when one male tries to mount the other, while occasionally the aggression aimed at an intruder is turned back on one of the partners. Bonded ganders (especially in trios) may also become “jealous” of the attentions their partner shows toward another bird. Some gander pairs are incestuous, as brothers may form long-term homosexual bonds. In addition, interspecies same-sex pairs also occur, for example between Greylag Geese and Mute Swans. Like Greylag-only gander pairs, these partnerships are long-lasting and distinguish themselves by their aggressiveness, with the two males frequently defending their territory against intruders.

Frequency: Homosexual couples constitute a significant proportion of pairs in Greylag Geese: an average of 14 percent of pairs in some populations are same-sex, and in some years this proportion can be even higher, with more than 20 percent of all pair-bonds consisting of ganders.

Orientation: Some Greylag males in gander pairs are exclusively homosexual, since they remain in a monogamous same-sex pair-bond for their entire lives (or re-pair with another gander on the death of their partner). Other males, however, are bisexual: some copulate with a female while remaining primarily bonded to a male (as described above), while others are involved in bisexual trios. Still other males alternate or switch between female and male partners over their lives—for example, ganders in heterosexual pairs sometimes find a male partner after the death of their mate. More than half of all widowers re-pair with a bird of the opposite sex, less than a third remain single, while the remainder form homosexual bonds.

Several variations on the monogamous, lifelong pair-bond occur in this species. Divorce occasionally happens: in some populations as many as a quarter of all females, for example, may abandon their mates and find a new gander, and overall, 5–8 percent of pairs divorce. Greylag Geese also sometimes form polygamous heterosexual trios, in which bonding occurs primarily between birds of the opposite sex—two males with a female or, more rarely, two females with a male. In addition, some families foster-parent chicks by combining broods with another family, while widowed ganders occasionally adopt goslings. Birds in heterosexual pairs may engage in promiscuous courtship and mating. Ganders sometimes try to mount females other than their mate, while females may pursue other males—much to the consternation of their mates, who often try to physically prevent them from engaging in “extramarital” activities. Although Greylag Geese become sexually mature in their third year, some one-year-olds form pair-bonds and even engage in courtship and sexual activity long before they begin breeding. Like homosexual pairs, heterosexual associations may also occur between related birds (especially parent-offspring), or birds of different species (e.g., with Canada Geese). However, sibling pairings are much less common among birds of the opposite sex.

*asterisked references discuss homosexuality/transgender

Ens, B. J., S. Choudhury, and J. M. Black (1996) “Mate Fidelity and Divorce in Monogamous Birds.” In J. M. Black, ed., Partnerships in Birds: The Study of Monogamy, pp. 344–401. Oxford: Oxford University Press.

Huber, R. (1988) “Sex-Specific Behavior in Greylag Geese, Anser anser L.” Texas Journal of Science 40:107–9.

*Huber, R., and M. Martys (1993) “Male-Male Pairs in Greylag Geese (Anser anser).” Journal für Ornithologie 134:155-64.

*Lorenz, K. (1991) Here Am I—Where Are You? The Behavior of the Greylag Goose. New York: Harcourt Brace Jovanovich.

*———(1979) The Year of the Greylag Goose. New York: Harcourt Brace Jovanovich.

Olsson, H. (1978) “Probable Polygamy in the Greylag Goose, Anser anser, and an Instance of Combined Broods.” Vår Fågelvårld 37:257–58.

*Schönfeld, M. (1985) “Beitrag zur Biologie der Schwane: ‘Männchenpaar’ zwischen Graugans und Hock-erschwan [Contribution to the Biology of Swans: ‘Male Pairing’ Between a Greylag Goose and a Mute Swan].” Der Falke 32:208.

Snow Geese are extremely gregarious and nest in dense colonies that can number in the thousands of birds; Canada Goose breeding grounds are generally less dense. In both species, birds usually pair in long-term, monogamous bonds (albeit with a number of variations—see below), and outside of the mating season they gather in large flocks.

Description:

Behavioral Expression: In Canada Geese, two birds of the same sex sometimes form a pair-bond. Both male and female homosexual pairs occur, and the partners may be either adults or juveniles; homosexual pair-bonds often persist for many years (as do heterosexual ones). Courtship behavior in the form of HEAD-DIPPING is frequently a part of such bonds: in this display, one bird ritually splashes water over the back of its head and neck by dipping its head deep into the water and then lifting it back up. In heterosexual contexts, this is often a prelude to copulation, but homosexual copulation is not a prominent feature of same-sex pairs. One exception involves trios: occasionally a bond forms between three birds—two females and one male—and sometimes one of the females will mount and copulate with the other female. Some lesbian pairs try to raise a family: one female in a homosexual pair, for example, built a nest and laid eggs while her partner stood guard, then the other female built her own nest next to the first and also laid eggs. None of the eggs hatched, however, because the females constantly rolled the eggs (which were probably not fertile in any case) back and forth between their nests and broke all of them.

More successful lesbian parenting occurs in Snow Geese. Pair-bonds between females are strong: when one member of the pair is absent from her mate, the other begins loudly calling to her until she returns. The pair builds a single nest in which each female lays eggs; as a result, such nests may have SUPERNORMAL CLUTCHES containing double the number of eggs found in heterosexual nests (8 eggs versus 4–5). Both birds take turns incubating the eggs (in heterosexual pairs, the male does not incubate). Since one or both females sometimes copulate with males, some of their eggs may be fertile. When they hatch, both females raise the goslings, including defending them against intruders and predators (such as Herring Gulls) by standing over them with cupped wings. Male homosexual pairs are not found in Snow Geese, although occasionally a cross-species pairing does develop between a male Snow Goose and a male Canada Goose. The two birds become constant companions, following one another and roosting close together, although nest-building and copulation do not usually take place. However, same-sex mounting does sometimes occur between male Snow Geese who take part in heterosexual “gang rapes.” In this species, males often sexually harass females, chasing them and forcing them to copulate. In some cases, other males gather together in large “spectator” groups—sometimes containing as many as 20–80 males—to watch and perhaps even join in. Occasionally, one male mounts another male as part of the group sexual activity that ensues.

Frequency: In Canada Geese, up to 12 percent of pairs in some (semiwild) populations are homosexual. The proportion is much smaller in Snow Geese: about 1 in 200 nests belongs to a pair of females. Approximately 4 percent of all mountings during Snow Goose rape attempts are between males.

Orientation: In one study of Canada Geese, 18 percent of the males formed homosexual pair-bonds while 6–12 percent of females did. Some birds in same-sex pairs appear to “prefer” their homosexual association, even if they have the opportunity for heterosexual interactions. In one case, a male harassed a female who was part of a long-lasting lesbian pair and separated her from her companion, mating with her. However, the next year she returned to her female partner and their pair-bond resumed. On the other hand, some birds have a preference for heterosexual pairings: many males remain unpaired if there are no available females rather than forming homosexual pair-bonds with each other. In Snow Geese, females in homosexual pairs may be functionally bisexual—they sometimes copulate with up to three different males to fertilize their eggs—although their same-sex pair-bond remains primary. Males who mount other males are otherwise primarily heterosexual, since most are paired with females and the majority of their sexual interactions are probably not with males.

As mentioned above, heterosexual rape is common in Snow Geese: during some mating seasons, each female is subjected to a rape attempt every five days (on average). Females are occasionally successful in thwarting such attacks, but males who rape can be very aggressive and may attack in groups. Sometimes the female’s mate can successfully chase an intruder off, but often he is not around to defend her because he is also raping another female. Significantly, most rapes are nonreproductive: more than 80 percent of all rape attempts are directed toward females that are nonfertilizable, such as incubating birds, and only about 2 percent of goslings are actually fathered this way. Rape is much less common among Canada Geese. However, ganders frequently harass and attack neighboring females when their mates are gone, often leading to abandonment of their eggs—as many as one-quarter of all nests may end up being deserted this way.

Several other variations on the heterosexual nuclear family occur in these species. Although most male-female pairs remain together for life, divorce and remating do occasionally take place in both Canada and Snow Geese. In addition, although most Snow Goose families remain together until the next breeding season, in some populations as many as 20 percent of the families split or break up before that time, usually because of separation of juveniles. Polygamous, heterosexual trios consisting of one male and two females sometimes form in Canada Geese (these differ from the bisexual trios described above in that the females are not bonded to each other). Some birds pair outside of their species, and Snow and Canada Geese may in fact mate with each other. CRÈCHES or combined broods—containing as many as 60 young—are sometimes found in Canada Geese, attended by one or several heterosexual pairs. In addition, families often “trade” goslings, caring for young other than their own on either a temporary or permanent basis. Up to 46 percent of Canada Goose broods and at least 13 percent of Snow Goose broods may contain adopted young, and over 60 percent of Canada broods in some populations experience a loss and/or gain of goslings due to adoption. Egg “adoption” is also common in Snow Geese because females often lay eggs in nests other than their own: 15–22 percent of all nests contain such eggs (although in some colonies more than 80 percent of nests may be affected), and more than 5 percent of all goslings are raised by a female other than their biological mother. Females that lay eggs in others’ nests are often aided by their mates, who distract the nest-owning gander by acting as a decoy for him to attack, allowing the female to approach the nest and lay her eggs. Sometimes the intruding female actually helps with building or repairing the nest; for her part, the nest-owning female often actively adopts foreign eggs that have not been laid directly in the nest by rolling them into her own clutch.

Snow Goose females also occasionally “abandon” their eggs by laying in what are known as DUMP NESTS, which contain large numbers of unincubated eggs from many different females. Abandonment of nests may also be triggered by the stresses of reproduction: females can lose up to a third of their body mass while incubating, and some individuals desert their clutches or even starve on the nest as a result of such hardships. Most Snow Goose nesting colonies also have a nonbreeding flock on their peripheries. In some years, the proportion of nonbreeding adults is sizable—as much as 40 percent of the population—and occasionally an entire colony will forgo breeding (for example if the weather is particularly adverse). Many Canada Goose heterosexual pairs are nonbreeding as well: in some populations, for example, more than a quarter of all male-female pairs do not procreate, although they may copulate frequently. In fact, some nonbreeders have sexual activity rates that are almost twice as high as pairs that do reproduce.

*asterisked references discuss homosexuality/transgender

*Allen, A. A. (1934) “Sex Rhythm in the Ruffed Grouse (Bonasa umbellus Linn.) and Other Birds.” Auk 51:180–99.

Ankney, C. D., and C. D. MacInnes (1978) “Nutrient Reserves and Reproductive Performance of Female Lesser Snow Geese.” Auk 95:459–71.

*Collias, N. E., and L. R. Jahn (1959) “Social Behavior and Breeding Success in Canada Geese (Branta canadensis) Confined Under Semi-Natural Conditions.” Auk 76:478-509.

*Conover, M. R. (1989) “What Are Males Good For?” Nature 342:624–25.

Cooke, E, and D. S. Sulzbach (1978) “Mortality, Emigration, and Separation of Mated Snow Geese.” Journal of Wildlife Management 42:271-80.

Cooke, F., M. A. Bousfield, and A. Sadura (1981) “Mate Change and Reproductive Success in the Lesser Snow Goose.” Condor 83:322–27.

*Diamond, J. M. (1989) “Goslings of Gay Geese.” Nature 340:101.

Ewaschuk, E., and D. A. Boag (1972) “Factors Affecting Hatching Success of Densely Nesting Canada Geese.” Journal of Wildlife Management 36:1097–106.

*Grether, G. F., and A. M. Weaver (1990) “What Are Sisters Good For?” Nature 345:392.

*Klopman, R. B. (1962) “Sexual Behavior in the Canada Goose.” Living Bird 1:123–29.

Lank, D. B., P. Mineau, R. F. Rockwell, and F. Cooke (1989) “Intraspecific Nest Parasitism and Extra-Pair Copulation in Lesser Snow Geese.” Animal Behavior 37:74-89.

Luekpe, K. (1984) “A Strange Goose: Canada-Snow Hybrid?” Passenger Pigeon 46:92.

MacInnes, C. D., R. A. Davis, R. N. Jones, B. C. Lieff, and A. J. Pakulak (1974) “Reproductive Efficiency of McConnell River Small Canada Geese.” Journal of Wildlife Management 38:686–707.

Martin, K., F. G. Cooch, R. F. Rockwell, and F. Cooke (1985) “Reproductive Performance in Lesser Snow Geese: Are Two Parents Essential?” Behavioral Ecology and Sociobiology 17:257–63.

^*Mineau, P., and F. Cooke (1979) “Rape in the Lesser Snow Goose.” Behavior 70:280–91.

Nastase, A. J., and D. A. Sherry (1997) “Effect of Brood Mixing on Location and Survivorship of Juvenile Canada Geese.” Animal Behavior 54:503–7.

Prevett, J. P. and C. D. MacInnes (1980) “Family and Other Social Groups in Snow Geese.” Wildlife Monographs 71:1–46.

*Quinn, T. W., J. C. Davies, F. Cooke, and B. N. White (1989) “Genetic Analysis of Offspring of a Female-Female Pair in the Lesser Snow Goose (Chen c. caerulescens).” Auk 106:177–84.

*Starkey, E. E. (1972) “A Case of Interspecific Homosexuality in Geese.” Auk 89:456–57.

Syroechkovsky, E. V. (1979) “Podkladyvaniye byelymi gusyami yaits v chuzhiye gnyezda [The Laying of Eggs by White Geese into Strange Nests].” Zoologichesky Zhurnal 58:1033—41.

Williams, T. D. (1994) “Adoption in a Precocial Species, the Lesser Snow Goose: Intergenerational Conflict, Altruism, or a Mutually Beneficial Strategy?” Animal Behavior 47:101–7.

Zicus, M. C. (1984) “Pair Separation in Canada Geese.” Wilson Bulletin 96:129–30.

Black Swans sometimes flock by the thousands and usually form mated pairs (although with numerous variations—see below) that nest either colonially or in separate territories. Mute Swans also generally develop long-term, monogamous bonds and nest in widely spaced territories, although some pairs form nesting colonies. Outside of the breeding season, they often associate in flocks.

Behavioral Expression: Some male Black Swans form stable, long-lasting homosexual pairs. Like heterosexual mates, same-sex partners often remain together for many years. The two males frequently perform the GREETING CEREMONY, a pair-bonding display that helps solidify and reinforce their partnership: the birds face one another, raise their wings (sometimes flapping them to expose the white feathers), and call repeatedly while extending their necks and lifting their bills up. Males in homosexual pairs also perform a courtship behavior known as HEAD-DIPPING. In this display—a prelude to copulation—the two birds repeatedly immerse first the head, then the neck, and finally the body in a wavelike fashion, sometimes for extended periods of 20–25 minutes. This can lead to homosexual mounting, although if one male does not want to participate in sexual activity he may respond aggressively to his partner’s overtures.

Male pairs of Black Swans fiercely defend territories that, during the mating season, are often significantly larger than those of heterosexual pairs. Because two males are able to pool their strength, they are more successful at chasing away other swans and can often annex a major portion of a pond (1,500–3,300 square feet) into their territory. In contrast, heterosexual pairs are often relegated to less favorable nesting areas and smaller territories (15–60 square feet). Homosexual pairs are also successful parents, acquiring nests and eggs in two different ways. Some male pairs associate temporarily with a female, building a nest together, mating with her, and then chasing her away once the eggs are laid, after which they begin parenting as a male couple. Other homosexual pairs chase heterosexual pairs from their nests and adopt the eggs that have already been laid. The two males incubate the clutch, hatch the eggs, and raise the chicks together. In fact, homosexual pairs are often more successful than heterosexual ones at raising chicks, in part because they have access to the best nesting sites and the largest territories, and probably because they also share incubation duties more equally. On average, 80 percent of homosexual parenting efforts are successful, compared to only about 30 percent of heterosexual ones.

Both male and female homosexual pairs occur in Mute Swans. In female pairs, both birds build a nest, lay eggs (which are usually infertile), and incubate the eggs. Sometimes one female stands guard over both the nest and her mate (as does the male in heterosexual pairs) and defends their territory. If their nest is disturbed by intruders, the females may begin a second nest and lay a new clutch of eggs, while still attending to the first as best they can. Male pairs also annually build nests together on which they take turns sitting, although unlike Black Swans they do not acquire any eggs. Male Mute Swans also sometimes form homosexual pair-bonds with other species, including Trumpeter Swans (Cygnus buccinator) and Greylag Geese.

Frequency: Overall, male couples constitute 5–6 percent of all pairings in Black Swans; in a given year, an average of 13 percent of the birds are in homosexual pair-bonds, and sometimes this proportion is as high as 20 percent. Homosexual parents account for 20–25 percent of all successful families. Same-sex bonds probably occur only sporadically in Mute Swans.

Orientation: Many Black and Mute Swans in same-sex pairs are probably exclusively homosexual, since they do not engage in heterosexual copulation or pairing and usually ignore unpaired birds of the opposite sex. However, some male pairs of Black Swans—while primarily homosexual—form short-lived bisexual trios in order to mate with females and thereby father their own offspring.

Populations of both Mute and Black Swans contain large proportions of nonbreeding birds. More than half of all Mute Swans are nonbreeders (as much as 89 percent of some populations), often gathering into their own flocks separate from breeding pairs. Many birds nest only once or twice during their entire lifetimes (which can last for 15–20 years), and a few never breed. Overall, only about a fifth of all Black Swans nest in any year, and in some populations more than 90 percent of the adults do not breed. Young, sexually mature Black Swans may remain with their parents and delay their breeding for many years (as long as three to eight years in some cases). On occasion, such a youngster will form an incestuous pair-bond with its parent: male Swans have been known to mate with their mother on the death of their father. Brother-sister and parent-offspring matings also occur in Mute Swans, as do heterosexual pairings with other species of swans (such as bewick’s, whistling, whooper, and Trumpeter) and geese (e.g., Snow, Canada, and Greylag). In fact, Black and Mute Swans may pair with each other, and trios of a male Black with two female Mute Swans have also been observed. Heterosexual trios within the same species are also common: about 14 percent of all bonds in Black Swans involve two males with a female, while Mute Swan trios are usually made up of two females with a male.

In addition to such polygamous associations, several other alternative family arrangements occur. “Foster parenting” or adoption takes place frequently among Black Swans (and occasionally in Mute Swans). In some colonies, more than two-thirds of all cygnets are raised in broods that combine offspring from 2–4 families (and occasionally from as many as 30 different families). Such BROOD AMALGAMATIONS—which may have up to 40 youngsters—are attended by a single pair of adults, who are not necessarily the biological parents of any of the cygnets. Adoption also occasionally occurs when adults “steal” eggs laid near their nest by other birds, rolling them into their own nest. Single parenting is a prominent feature of Black Swan social life: often a male or female deserts its mate during incubation, and in some colonies the majority of nests are attended by single parents. Occasionally, a pair “separates” rather than divorces, with one bird taking the newly hatched young while the other remains to incubate the rest of the eggs. Among Mute Swans, the divorce rate is 3–10 percent of all pairs, and about a fifth of all birds have two to four mates during their lifetime. Some Mute Swans are nonmonogamous, courting or mating with another bird while remaining paired with their partner; some of this activity may involve REVERSE copulations (in which the female mounts the male). Many within-pair copulations are nonprocreative, since most pairs mate far more often than is required for fertilization of the eggs. Swans also sometimes engage in behaviors that are counterreproductive. A third of all Black Swan eggs, for example, are lost through abandonment of the nest by the parent (s), while 3 percent of Mute Swan parents desert their nests, and birds often attack and even kill youngsters that stray into their territory. Eggs are sometimes also destroyed during territorial disputes, and adult birds may be killed as a direct result of such attacks as well (accounting for 3 percent of all deaths).

*asterisked references discuss homosexuality/transgender

Bacon, P. J., and P. Andersen-Harild (1989) “Mute Swan.” In 1. Newton, ed., Lifetime Reproduction in Birds, pp. 363–86. London: Academic Press.

Braithwaite, L. W. (1982) “Ecological Studies of the Black Swan. IV. The Timing and Success of Breeding on Two Nearby Lakes on the Southern Tablelands of New South Wales.” Australian Wildlife Research 9:261–75.

*———(1981) “Ecological Studies of the Black Swan. III. Behavior and Social Organization.” Australian Wildlife Research 8:135–46.

*———(1970) “The Black Swan.” Australian Natural History 16:375-79.

Brugger, C., and M. Taborsky (1994) “Male Incubation and Its Effect on Reproductive Success in the Black Swan, Cygnus atratus.” Ethology 96:138–46.

Ciaranca, M. A., C. C. Allin, and G. S. Jones (1997) “Mute Swan (Cygnus olor).” In A. Poole and F. Gill, eds., The Birds of North America: Life Histories for the 21st Century, no. 273. Philadelphia: Academy of Natural Sciences; Washington, D.C.: American Ornithologists’ Union.

Dewer, J. M. (1942) “Ménage à Trois in the Mute Swan.” British Birds 30:178.

Huxley, J. S. (1947) “Display of the Mute Swan.” British Birds 40:130–34.

*Kear, J. (1972) “Reproduction and Family Life.” In P. Scott, ed., The Swans, pp. 79–124. Boston: Houghton Mifflin.

*Low, G. C. and Marquess of Tavistock (1935) “The Extent to Which Captivity Modifies the Habits of Birds.” Bulletin of the British Ornithologists’ Club 55:144–54.

Mathiasson, S. (1987) “Parents, Children, and Grandchildren—Maturity Process, Reproduction Strategy, and Migratory Behavior of Three Generations and Two Year-Classes of Mute Swans Cygnus olor.” In M. O. G. Eriksson, ed., Proceedings of the Fifth Nordic Ornithological Congress, 1985, pp. 60–70. Acta Regiae Societatis Scientiarum et Litterarum Gothoburgensis Zoologica no. 14. Göteborg: Kungl. Vetenskaps- och Vitterhets-Samhället.

Minton, C. D. T. (1968) “Pairing and Breeding of Mute Swans.” Wildfowl 19:41–60.

*O’Brien, R. M. (1990) “Black Swan, Cygnus atratus.” In S. Marchant and P. J. Higgins, eds., Handbook of Australian, New Zealand, and Antarctic Birds, vol. 1, pp.1178–89. Melbourne: Oxford University Press.

Ogilvie, M. A. (1972) “Distribution, Numbers, and Migration.” In P. Scott, ed., The Swans, pp. 29–55. Boston: Houghton Mifflin.

Rees, E. C., P. Lievesley, R. A. Pettifor, and C. Perrins (1996) “Mate Fidelity in Swans: An Interspecific Comparison.” In J. M. Black, ed., Partnerships in Birds: The Study of Monogamy, pp. 118–37. Oxford: Oxford University Press.

*Ritchie, J. P. (1926) “Nesting of Two Male Swans.” Scottish Naturalist 159:95.

*Schönfeld, M. (1985) “Beitrag zur Biologie der Schwane: ‘Männchenpaar’ zwischen Graugans und Hock-erschwan [Contribution to the Biology of Swans: ‘Male Pairing’ Between a Greylag Goose and a Mute Swan].” Der Falke 32:208.

Sears, J. (1992) “Extra-Pair Copulation by Breeding Male Mute Swan.” British Birds 85:558–59.

*Whitaker, J. (1885) “Swans’ Nests.” The Zoologist 9:263–64.

Williams, M. (1981) “The Demography of New Zealand’s Cygnus atratus Population.” In G. V. T. Matthews and M. Smart, eds., Proceedings of the 2nd International Swan Symposium (Sapporo, Japan), pp. 147–61. Slimbridge: International Waterfowl Research Bureau.

Mallard Ducks and Blue-winged Teals are highly sociable birds, usually congregating in their own flocks of hundreds or (in Mallards) even thousands for most of the year. During the breeding season, they typically form monogamous pairs, although many variations exist. As in many other duck species, heterosexual pairs usually separate soon after incubation begins. Females then incubate the eggs and raise their families on their own.

Behavioral Expression: Female Mallards sometimes mount and copulate with other females in the early fall, when ducks congregate in groups and begin to establish pair-bonds. Two females may engage in the PUMPING display, a prelude or invitation to mating in which the head is bobbed up and down so that the bill touches the water in a horizontal position. Following this, one female flattens her body on the water and extends her neck, allowing the other female to mount. While copulating, the mounting female may grab her partner’s neck feathers in her bill or gently peck at her head. After dismounting, she performs a concluding display (also shown by females in heterosexual interactions) in which she dips her head in the water and then shakes the drops down her back while beating her wings. Homosexual mountings occasionally occur later in the season between heterosexually paired females and single females.

Homosexual pair-bonds also occur in both male and female Mallards. As in heterosexual pairs, the two partners keep close company, swimming together as well as resting, preening, and feeding in perfect synchrony. Same-sex partners also “defend” their mate from the approach of other Mallards. Females use a special INCITING display for this, in which they trail their partner while looking back over their shoulder and making a trembling call. Overt sexual activity is not generally a feature of same-sex partnerships, however: drake pairs, for example, engage in mutual head pumping and feather ruffling (which are preludes to copulation) but neither partner mounts the other or invites his mate to mount him. Interestingly, though, some males in homosexual pairs have been observed attempting to rape or forcibly copulate with males outside their pair-bond (just the way drakes in heterosexual pairs often participate in nonmonogamous raping of females—see below). Among females, homosexual pair-bonds are more ephemeral, generally occurring only in the pre-and postbreeding seasons. Some drake pairs are also temporary, while others are long-lasting, persisting for years and possibly even for life.

Male Mallards that have been raised together also frequently develop homosexual bonds of great strength and longevity. When large numbers of such birds are present, they often form their own groups, known as CLUBS. They flock together for hours or even days at a time, excitedly running about and swimming together while quacking continuously. Sometimes a female associates herself with a drake pair to form a bisexual trio; although one or both males may mate with her, their homosexual bond remains primary. Less commonly, females that have been raised together may also form a pair-bond, jointly incubating a nest and coparenting any ducklings that may result from promiscuous matings with males.

Blue-winged Teal drakes will court each other in the absence of females, even competing and fighting with one another for the attentions of another male.

Frequency: Homosexual copulations and pairings between female Mallard Ducks occur sporadically and are most common during the fall. In one study, roughly a quarter of the days on which sexual activity was observed included same-sex mountings. The proportion of male homosexual pairs varies between populations, anywhere from 2–19 percent of all pairs.

Orientation: Several forms of bisexuality occur among Mallards: females may participate in homosexual copulations while paired with a male, and both sexes may form seasonal homosexual attachments prior to or following a period of heterosexual mating. Some males are probably more exclusively homosexual, forming ongoing same-sex bonds that last for many years. In addition, most males probably have a bisexual potential: when raised in all-male groups, Mallards usually form lifelong homosexual pairs, and re-pair with other males on being “widowed.” Nevertheless, even among males that have not been raised together, approximately 13–17 percent still participate in homosexual pairing for at least a portion of their lives. In Blue-winged Teals, homosexual behavior appears to be primarily a manifestation of a bisexual potential, since same-sex pairing or courtship have so far only been observed in males isolated from females.

Mallard pairs regularly engage in nonreproductive matings. For example, copulation is common during the five-to-seven months that heterosexual couples are together prior to the breeding season (when males are not producing sperm). Later in the breeding season, however, male-female relations are often marked by hostility, since forced copulation or rape is a common feature of opposite-sex interactions in both Mallards and Blue-winged Teals. Following egg-laying, male Mallards regularly abandon their female mates (who thus become “single parents”), congregate in all-male groups, and begin pursuing other females to try to forcibly mate with them. Rapes also occur between paired ducks in both species. As many as a 12–40 males may chase a single female in aerial or aquatic pursuit; drakes have even been known to grab and mount females underwater when they dive (attempting to escape), or to knock females to the ground in midflight. In some populations, as many as 7–10 percent of all females die each year as a result of drownings or other injuries incurred during rapes. Occasionally, males even try to mate with dead females. Even while they are still paired earlier in the breeding season, males frequently court and attempt to mate with (or rape) females other than their mate. About 3–7 percent of offspring are a result of such nonmonogamous matings, and in some populations multiple parentage occurs in at least 17–25 percent of all broods.

Mallards also sometimes form trio-bonds, either one male with two females (2–4 percent of all heterosexual bonds) or, more commonly, two males with one female (3–6 percent of all bonds). Paired males sometimes switch mates during the breeding season as well, and at least 9 percent of all heterosexual couples divorce between breeding seasons. Overall, long-term male-female pair-bonds (lasting two or more seasons) are rare in this species. Mallard mothers can be extremely aggressive in defense of their young, even killing other youngsters that stray from their own broods. In some populations the greatest cause of mortality among ducklings is attacks from other mothers. Occasionally, however, two broods join together and are defended by a single mother for short periods.

Homosexual pairs also form among male Wood Ducks (Aix sponsa) that are raised together; such pairs are lifelong, and the two males may even search for nesting sites together each year. Female Chiloe Wigeons (Anas sibilatrix) have also been known to pair together in captivity; the partners remain bonded for many years and each lays eggs in their nest.

*asterisked references discuss homosexuality/transgender

Bailey, R. O., N. R. Seymour, and G. R. Stewart (1978) “Rape Behavior in Blue-winged Teal.” Auk 95:188-90.

Barash, D. P. (1977) “Sociobiology of Rape in Mallards (Anas platyrhynchos): Responses of the Mated Male.” Science 197:788–89.

Boos, J. D., T. D. Nudds, and K. Sjöberg (1989) “Posthatch Brood Amalgamation by Mallards.” Wilson Bulletin 101:503–5.

*Bossema, I., and E. Roemers (1985) “Mating Strategy, Including Mate Choice, in Mallards.” Ardea 73:147–57.

Cheng, K. M., J. T. Burns, and F. McKinney (1983) “Forced Copulation in Captive Mallards. III. Sperm Competition.” Auk 100:302-10.

Evarts, S., and C. J. Williams (1987) “Multiple Paternity in a Wild Population of Mallards.” Auk 104:597–602.

*Geh, G. (1987) “Schein-Kopula bei Weibchen der Stockente Anas platyrhynchos [Pseudo-Copulation of Female Mallard Ducks].” Anzeiger der Ornithologischen Gesellschaft in Bayern 26:131–32.

*Hochbaum, H. A. (1944) The Canvasback on a Prairie Marsh. Washington, D.C.: American Wildlife Institute.

Huxley, J. S. (1912) “A ‘Disharmony’ in the Reproductive Habits of the Wild Duck (Anas boschas L.).” Biologisches Centralblatt 32:621–23.

*Lebret, T. (1961) “The Pair Formation in the Annual Cycle of the Mallard, Anas platyrhynchos L.” Ardea 49:97–157.

*Lorenz, K. (1991) Here Am I—Where Are You? The Behavior of the Greylag Goose. New York: Harcourt Brace Jovanovich.

*———(1935) “Der Kumpan in der Umwelt des Vögels.” Journal für Ornithologie 83:10–213, 289–413. Reprinted as “Companions as Factors in the Bird’s Environment.” In K. Lorenz (1970), Studies in Animal and Human Behavior, vol. 1, pp. 101-258. Cambridge, Mass.: Harvard University Press.

Losito, M. P., and G. A. Baldassarre (1996) “Pair-bond Dissolution in Mallards.” Auk 113:692-95.

McKinney, F., S. R. Derrickson, and P. Minneau (1983) “Forced Copulation in Waterfowl.” Behavior 86:250–94.

Mjelstad, H., and M. Sætersdal (1990) “Reforming of Resident Mallard Pairs Anas platyrhynchos, Rule Rather Than Exception?” Wildfowl 41:150–51.

Raitasuo, K. (1964) “Social Behavior of the Mallard, Anas platyrhynchos, in the Course of the Annual Cycle.” Papers on Game Research (Helsinki) 24:1-72.

*Ramsay, A. O. (1956) “Seasonal Patterns in the Epigamic Displays of Some Surface-Feeding Ducks.” Wilson Bulletin 68:275–81.

*Schutz, F. (1965) “Homosexualität und Pragung: Eine experimentelle Untersuchung an Enten [Homosexuality and Developmental Imprinting: An Experimental Investigation of Ducks].” Psychologische Forschung 28:439–63.

*Titman, R. D., and J. K. Lowther (1975) “The Breeding Behavior of a Crowded Population of Mallards.” Canadian Journal of Zoology 53:1270–83.

Weston, M. (1988) “Unusual Behavior in Mallards.” Vogeljaar 36:259.

Williams, D. M. (1983) “Mate Choice in the Mallard.” In P. Bateson, ed., Mate Choice, pp. 33–50. Cambridge: Cambridge University Press.

Lesser Scaup Ducks are highly social, gathering into large waterborne flocks or “rafts” that may number in the tens of thousands. They form pair-bonds during the mating season, but males typically leave their mates following egg-laying (see below) and join large all-male groups. Australian Shelducks also form mated pairs during the breeding season (both parents care for the young) but otherwise associate in flocks. Musk Ducks are largely solitary except during the mating season; adult males are territorial, and they are probably polygamous or promiscuous (copulating with more than one female).

Behavioral Expression: Male Lesser Scaup Ducks occasionally try to copulate with one another; drakes who participate in such homosexual activity are usually unpaired birds. While same-sex mounting does not occur among females, coparenting does. In this species, males usually abandon their female mates shortly after incubation of the eggs begins. Most females take care of their young entirely on their own as single parents, but sometimes two females join together and help each other raise their families. Accompanying their combined broods of 20 or more ducklings, the two females cooperate in all parental duties, including coordinated defense of the youngsters. If a predator or intruder approaches, one female distracts it by boldly approaching and feigning an injury, while her partner stealthily leads all of the ducklings away to safety. As their offspring get older, however, female coparents show less of this “distraction” behavior; at the approach of a predator, they may depart with one another and temporarily leave their ducklings behind to fend for themselves. Occasionally three females join forces and raise their combined broods—as many as 50 or more ducklings—as a parenting trio. Interestingly, duckling survival rates are not significantly different in families with one as opposed to two (or three) female parents.

Female Australian Shelducks often court one another and form homosexual pair-bonds. In December, when birds begin pairing, females display to each other with ritual preening movements and chases. These often develop into a full-fledged WATER-THRASHING DISPLAY, in which one female swims toward the other while making sideways pointing movements with her outstretched head and neck. She may also dive and resurface, then chase after the other female. Her partner is frequently captivated by this performance and responds by enthusiastically diving and chasing in return; the two females may, as a result, form a bond that lasts until the next pairing season. Females that engage in homosexual courtship and pairing are usually younger adult or juvenile birds.

Male Musk Ducks perform an extraordinary courtship display that attracts both males and females. The male arches his back and lifts his head up, engorging his large throat pouch; at the same time he fans and bends his tail forward over his back at an extreme angle—a feat made possible because of two extra vertebrae. This gives the bird an astounding, reptilian appearance. While in this posture, he kicks both feet backward or to the side, producing enormously loud splashes or jets of water. Multiple kicks of various types are given in series, and often the courting male rapidly back-paddles in between kicks. He also produces a wide variety of sounds during these PADDLE-KICK, PLONK-KICK, and WHISTLE-KICK displays, including ker-plonks (made by the kicking and splashing) combined with whirr or cuc-cuc vocalizations, and even a distinctive whistling sound. In addition, many displaying males emit a musky odor (hence the name of the bird), and their plumage is so oily that puddles of oil may form on the surface of the water around them. This display—perhaps one of the most dramatic of all birds—draws both males and females, who crowd around the courting male. Often, males appear to be more attracted than females, swimming much closer to the displaying male and sometimes even making physical contact by gently and repeatedly nudging their breast against his shoulder. The displaying male is in a trancelike state and rarely responds directly to any of the onlookers. Indeed, although homosexual copulation has not been observed as a part of these displays, heterosexual mating has hardly ever been seen during such courtship sessions either.

Frequency: Homosexual mounting probably occurs only occasionally in Lesser Scaup Ducks, but female coparenting is a regular feature of some populations. As many as a quarter to a third or more of all families have two mothers, although in other populations they are less frequent, comprising about 12 percent of families in some years. Same-sex courtship and pairing occur frequently among younger Australian Shelduck females, while male Musk Ducks are routinely attracted to displaying males.

Orientation: A variety of bisexual arrangements characterize these duck species. Some female Lesser Scaups (perhaps 30–40 percent of the population) have a seasonal alternation between same-sex and opposite-sex pairings: they begin the breeding season in heterosexual pairs, but end it in same-sex associations. Most Australian Shelduck females in homosexual pairs probably go on to form heterosexual bonds as adults. Musk Duck males display to both females and other males; some of the males they attract are also interested in females, but others are apparently only attracted to the courting male.

As described above, separation of heterosexual pairs with subsequent female single-parenting (or coparenting) is the usual pattern for Lesser Scaup families. Several other alternative parenting and pairing arrangements occur in these species. Occasionally a female Lesser Scaup associates with a mated pair and even lays eggs in their nest. Musk Ducks often lay their eggs in other birds’ nests, where they are foster-parented by both their own and foreign species—including many other kinds of ducks (e.g., the blue-billed duck, Oxyura australis) as well as Dusky Moorhens. For their part, Lesser Scaups occasionally raise ducklings of other species of ducks, hatched from eggs that have been laid in their nests by, for example, redheads (Aythya americana). Australian Shelducks sometimes foster-parent chicks as well: about 5 percent of all broods contain “extra” ducklings from other families, and about 1 percent of all ducklings are adopted or “exchanged” between families. Lesser Scaup ducklings are occasionally abandoned by their mothers and may be adopted into other families. Abandonment of eggs is also prevalent: female Lesser Scaups may desert entire clutches, while egg DUMPING is common in Australian Shelducks. Many Shelduck pairs copulate but then lay or abandon the resulting eggs in caves, along the shore, or on islands, never incubating or hatching them. Most of these pairs—who may constitute close to half the population—have been unable to secure a breeding territory of their own. Many other birds are non-breeders as well: a large proportion of Lesser Scaups of both sexes, and Australian Shelduck females, are younger birds that are sexually mature but unpaired. In addition, it is thought that reproduction in younger male Musk Ducks may be suppressed by the presence of older males.

Although many Australian Shelducks form long-lasting heterosexual bonds, about 10 percent of breeding pairs divorce, and many more juvenile pairs separate. In Lesser Scaups, nonmonogamous copulations are common, accounting for more than half of all heterosexual activity. Many of these are rapes or forced copulations performed by paired males on females other than their mate; occasionally groups of up to eight males will pursue a female and try to mate with her. Only about 20 percent of such rapes involve penetration—the male Lesser Scaup, like most waterfowl (but unlike most other birds), does have a penis. More than a quarter of all such attempts are nonreproductive, occurring too early in the breeding season, during incubation, after breeding, or on nonbreeding females. In fact, the highest rates of attempted rape occur on females just before their molting period, when they are nonfertilizable. In Australian Shelducks, it is the females who vigorously pursue males, often courting already paired drakes in dramatic aerial chases. One or several females may try to maneuver in between a mated pair to separate the male, even grabbing at the tail feathers of his mate to force her to change direction. Females frequently suffer broken wings and may even be killed when they hit obstacles during such high-speed chases.

Interspecies homosexual pairs involving several other kinds of ducks and geese have been observed in captive birds. A pair consisting of a female Common Shelduck (Tadorna tadorna) with a female Egyptian Goose (Alopochen aegyptiacus), for example, both laid eggs in a shared nest and jointly incubated them.

*asterisked references discuss homosexuality/transgender

*Afton, A. D. (1993) “Post-Hatch Brood Amalgamation in Lesser Scaup: Female Behavior and Return Rates, and Duckling Survival.” Prairie Naturalist 25:227-35.

———(1985) “Forced Copulation as a Reproductive Strategy of Male Lesser Scaup: A Field Test of Some Predictions.” Behavior 92:146–67.

———(1984) “Influence of Age and Time on Reproductive Performance of Female Lesser Scaup.” Auk 101:255–65.

Attiwell, A. R., J. M. Bourne, and S. A. Parker (1981) “Possible Nest-Parasitism in the Australian Stiff-Tailed Ducks (Anatidae: Oxyurini).” Emu 81:41–42.

Bellrose, F. C. (1976) Ducks, Geese, and Swans of North America. Harrisburg, PA: Stackpole.

Fullagar, P. J., and M. Carbonell (1986) “The Display Postures of the Male Musk Duck.” Wildfowl 37:142–50.

Gehrman, K. H. (1951) “An Ecological Study of the Lesser Scaup Duck (Aythya affinis Eyton) at West Medical Lake, Spokane County, Washington.” Master’s thesis, State College of Washington (Washington State University).

*Hochbaum, H. A. (1944) The Canvasback on a Prairie Marsh. Washington, D.C.: American Wildlife Institute.

*Johnsgard, P. A. (1966) “Behavior of the Australian Musk Duck and Blue-billed Duck.” Auk 83:98–110.

*Low, G. C., and Marquess of Tavistock (1935) “The Extent to Which Captivity Modifies the Habits of Birds.” Bulletin of the British Ornithologists’ Club 55:144–54.

*Lowe, V. T. (1966) “Notes on the Musk Duck Biziura lobata.” Emu 65:279–89.

*Munro, J. A. (1941) “Studies of Waterfowl in British Columbia: Greater Scaup Duck, Lesser Scaup Duck.” Canadian Journal of Research, section D 19:113–38.

O’Brien, R. M. (1990) “Musk Duck, Biziura lobata.” In S. Marchant and P. J. Higgins, eds., Handbook of Australian, New Zealand, and Antarctic Birds, vol. 1, pp. 1152–60. Melbourne: Oxford University Press.

Oring, L. W. (1964) “Behavior and Ecology of Certain Ducks During the Postbreeding Period.” Journal of Wildlife Management 28:223–33.

*Riggert, T. L. (1977) “The Biology of the Mountain Duck on Rottnest Island, Western Australia.” Wildlife Monographs 52:1–67.

Rogers, D. I. (1990) “Australian Shelduck, Tadorna tadornoides.” In S. Marchant and P. J. Higgins, eds., Handbook of Australian, New Zealand, and Antarctic Birds, vol. 1, pp. 1210-18. Melbourne: Oxford University Press.

OTHER AQUATIC BIRDS

Common Murres and Laysan Albatrosses spend eight to nine months of the year at sea (often in large flocks for Murres). The remainder of the time, they gather at traditional nesting sites in extraordinary densities—Murre colonies, for example, can contain hundreds of thousands of pairs. The mating system is a combination of long-term pair-bonds and promiscuous copulations.

Behavioral Expression: Male Common Murres—usually heterosexually paired—often try to copulate with birds other than their mate, including other males. Homosexual mountings—like heterosexual promiscuous mountings—are usually performed on birds returning to the colony after having been away (for example, while feeding). Immediately upon spotting an arriving male (or female), another male runs toward him, making a harsh, yodel-like crowing sound. He then hooks his neck around the other male and attempts to copulate with him. The other male usually prevents or resists the mounting attempt by standing upright, running away, or directly attacking him. Homosexual mountings also take place during “gang rape” attempts, which occur in 20–30 percent of all promiscuous matings. Groups of males—sometimes as many as ten at a time—gather to try to forcibly copulate with the same female, and occasionally males also mount each other during the ensuing sexual activity.

A similar form of rape occurs among Laysan Albatrosses. Early in the breeding season, males often leave their partner’s side to try to copulate with males or females that are passing through the breeding colony. This is especially true if they momentarily and inadvertently spread and droop their wings (signals usually given by a female before copulation). Groups of five or six males often pursue the same individual, all jostling to mount him or her; typically a male will hook his bill across the neck of the bird being pursued, to throw it off balance. Homosexual mountings are common in these group rape attempts, and “pile-ups” or stacks of up to four males mounted on top of each other have been observed. Rape attempts—whether on males or females—never result in ejaculation, since the bird being mounted always resists the advances of the pursuing bird. A completely different homosexual activity also occurs in this species: occasionally two birds of the same sex perform an elaborate courtship dance with one another. This complex synchronized display involves more than 25 different postures. The two birds stand facing each other, stretching their heads upward during SKY CALLS and SKY MOOS, clap their bills, and bow, strut, and circle around their partner, all the while making a cacophony of clicking, whinnying, wailing, and grunting sounds.

Frequency: At least 5–6 percent of all promiscuous mating attempts on arriving Common Murres are homosexual, and one out of ten arriving males is mounted by another male (compared to three out of four arriving females). Homosexual copulation attempts probably represent 1 percent or less of all mountings (both promiscuous and between pair-bonded birds). In Laysan Albatrosses, rape attempts are frequent before egg laying and probably occur with equal regularity on males and females. Approximately 9 percent of courtship dances take place between two females and 4 percent between two males.

Orientation: About two-thirds of all male Common Murres participate in promiscuous copulations; only a fraction of these engage in homosexual mountings. Male Laysan Albatrosses are as likely to pursue and mount other males as females in their rape attempts. Although it is difficult to draw firm conclusions without detailed study of individual birds, most males that engage in homosexual behavior in these species are probably functionally bisexual, since they are usually already paired with a female (although a few Common Murres who participate in such activity may be unpaired). However, their primary orientation is probably heterosexual since relatively few of their sexual interactions are with other males. The same probably holds for males being mounted by other males: because they usually resist forced mounts by other males, it is likely that most such males are heterosexually oriented. However, most females also resist forced mountings by males, so it is possible that males are reacting negatively to the forced nature of the copulation attempt, as much if not more so than to the sex of the bird mounting them.

As mentioned above, promiscuous copulations occur frequently in these species. About 10 percent of all Common Murre matings are forced copulations between a male and a female other than his partner, and on some days each female is subjected to such a rape attempt nearly every hour. Females usually respond aggressively to such attacks, and their mates also try to defend them, although sometimes an intruding male will actually disrupt a copulation between a mated pair by knocking the male off his partner’s back. In about 15 percent of all promiscuous matings, the female does not react aggressively and appears to cooperate in allowing the male to make genital contact. Female Laysan Albatrosses always resist rape attempts and may be severely injured in the process: one female was attacked by four different gangs of males in ten minutes, losing an eye and sustaining severe wing injuries. However, forced copulations in this species are always nonprocreative since sperm is never transferred. Many promiscuous matings in Common Murres are nonreproductive as well: cloacal contact often does not occur (less than 1 in 200 such matings result in insemination), and during group promiscuous matings, males often mount on any part of the female’s body, including her head. In addition, about 15–30 percent of promiscuous copulations occur outside of the female’s fertile period. The same is also true for sexual activity between mated partners: copulation begins as long as four to five months before the start of egg laying, and half of all heterosexual matings in some populations occur during nonfertilizable periods. In addition, almost a quarter of pair copulations do not involve genital contact. In Common Murres—as in most other birds—females have the remarkable ability to store sperm in special ducts in their reproductive tract, allowing them to inseminate their eggs even when not directly engaging in reproductive copulations.

Other forms of nonprocreative sexuality also occur. Nonbreeding female Common Murres often solicit promiscuous matings from males, while nonbreeding pairs or those who have lost their young (which can make up as much as a third of all pairs) frequently continue to copulate throughout the season. Nonbreeding Laysan Albatross pairs also sometimes engage in copulation. Birds in this species do not reproduce until they are 6–16 years old, even though they mature at one year old and may form pairs fully two years before they actually breed. Similarly, younger Common Murres usually delay breeding until they are five years old, congregating in CLUBS on the tidal rocks beneath the breeding colonies. Such nonbreeders make up approximately 13 percent of the population; among adults, 5–10 percent of birds do not breed each year, and more than a third skip breeding for at least one season during their life. In addition, masturbatory activity—birds mount and “copulate” with clumps of grass—was recently discovered in a closely related species, the thick-billed murre (Uria lomvia); it is likely that similar behavior also occurs in Common Murres.

A variety of alternative parenting arrangements are also found in these species. About 8 percent of all Common Murre chicks have “baby-sitters”—a pair of birds other than their parents who help brood (keep warm), protect, and sometimes feed the chick (even when the youngster’s parents are not away). Most such helpers are nonbreeders; others have tried but failed to breed, while some have finished raising their family or are also taking care of their own chick. In addition, pair separation and single parenting is routine in Common Murres: when a chick is old enough to leave the colony, only its father accompanies it to sea, feeding and chaperoning it for up to 12 weeks without his female partner. In Laysan Albatrosses, heterosexual parents are together at the nest for a remarkably short time—only 5–10 days out of the 230-day breeding season. Eggs are sometimes temporarily “adopted” by other birds who incubate them when the parents are away from the nest. Nonbreeding females have even been known to “join” existing pairs and regularly take turns with the parents incubating their egg. Sometimes females also lay a second egg in a stranger’s nest. Reproduction in this species is often fraught with difficulties, however. More than 20 percent of parents (both males and females) desert their nests—often when their partner fails to return for an incubation shift on time—and couples also occasionally divorce (2 percent of all pairs). Once the chicks have hatched, they are often subjected to abuse from neighboring birds, who may savagely peck, stab, bite, and occasionally even kill the youngsters if they stray too close.

Homosexual copulations are common in another species of auk, the Razorbill (Alca torda), where 41 percent of nonmonogamous mountings (about 18 percent of all mountings) are between males. Up to 200 or more such mountings have been observed each season in some populations. Nearly two-thirds of all males mount other males (an average of 5 partners, sometimes as many as 16) and more than 90 percent of males receive mounts from other males. Older males participate more often than younger ones, and mountings are occasionally reciprocal. Like females, males usually resist such promiscuous mating attempts: although the mounter usually tries to achieve cloacal (genital) contact, only about 1 percent of same-sex mountings include genital contact or ejaculation (compared to 12 percent of promiscuous heterosexual mounts).

*asterisked references discuss homosexuality/transgender

Birkhead, T. R. (1993) Great Auk Islands. London: T. and A.D. Poyser.

*———(1978a) “Behavioral Adaptations to High Density Nesting in the Common Guillemot Uria aalge.” Animal Behavior 26:321—31.

———(1978b) “Attendance Patterns of Guillemots Uria aalge at Breeding Colonies on Skomer Island.” Ibis 120:219-29.

Birkhead, T. R., and P. J. Hudson (1977) “Population Parameters for the Common Guillemot Uria aalge.” Ornis Scandinavica 8:145—54.

Birkhead, T. R., S. D. Johnson, and D. N. Nettleship (1985) “Extra-pair Matings and Mate Guarding in the Common Murre Uria aalge.” Animal Behavior 33:608—19.

Birkhead, T. R., and D. N. Nettleship (1984) “Alloparental Care in the Common Murre (Uria aalge).” Canadian Journal of Zoology 62:2121—24.

Fisher, H. I. (1975) “The Relationship Between Deferred Breeding and Mortality in the Laysan Albatross.” Auk 92:433—41.

*———(1971) “The Laysan Albatross: Its Incubation, Hatching, and Associated Behaviors.” Living Bird 10:19—78.

———(1968) “The ‘Two-Egg Clutch’ in the Laysan Albatross.” Auk 85:134—36.

Fisher, H. I., and M. L. Fisher (1969) “The Visits of Laysan Albatrosses to the Breeding Colony.” Micronesica 5:173—221.

Fisher, M. L. (1970) The Albatross of Midway Island: A Natural History of the Laysan Albatross. Carbondale, Ill.: Southern Illinois University Press.

*Frings, H., and M. Frings (1961) “Some Biometric Studies on the Albatrosses of Midway Atoll.” Condor 63:304—12.

Gaston, T., and K. Kampp (1994) “Thick-billed Murre Masturbating on Grass Clump.” Pacific Seabirds 21:30.

Harris, M. P., and S. Wanless (1995) “Survival and Non-Breeding of Adult Common Guillemots Uria aalge.” Ibis 137:192-97.

*Hatchwell, B. J. (1988) “Intraspecific Variation in Extra-pair Copulation and Mate Defence in Common Guillemots Uria aalge.” Behavior 107:157-85.

Hudson, P. J. (1985) “Population Parameters for the Atlantic Alcidae.” In D. N. Nettleship and T. R. Birkhead, eds., The Atlantic Alcidae, pp. 233—61. London: Academic Press.

Johnson, R. A. (1941) “Nesting Behavior of the Atlantic Murre.” Auk 58:153—63.

Meseth, E. H. (1975) “The Dance of the Laysan Albatross, Diomedea immutabilis.” Behavior 54:217-57.

Rice, D. W., and K. W. Kenyon (1962) “Breeding Cycles and Behavior of Laysan and Black-footed Albatrosses.” Auk 79:517-67.

Tuck, L. M. (1960) The Murres: Their Distribution, Populations, and Biology. Ottawa: Canadian Wildlife Service.

*Wagner, R. H. (1996) “Male-Male Mountings by a Sexually Monomorphic Bird: Mistaken Identity or Fighting Tactic?” Journal of Avian Biology 27:209—14.

———(1991) “Evidence That Female Razorbills Control Extra-Pair Copulations.” Behavior 118:157-69.

Great Cormorants and Shags form mated pairs and generally nest in colonies, which may contain as many as 20,000 pairs in some populations of Great Cormorants. Outside of the mating season, these species are moderately gregarious, wandering solitarily but sometimes forming flocks.

Behavioral Expression: Homosexual pairs consisting of two males sometimes form in Great Cormorants and last for up to five years (heterosexual pairs in this species are usually seasonal but may also last for several years). Male pairs often build oversize nests because both birds contribute to the construction of the nest. They often sit on the nest as if incubating eggs; similar behavior is also seen in heterosexual pairs prior to egg laying. In some homosexual pairs, one partner may use vocalizations that are typical of females (such as panting or purring sounds), or else calls that are intermediate between male and female vocal patterns. Male pairs are sometimes incestuous, composed of two brothers.

In European Shags, males occasionally court other males. As one male approaches—hopping along the rocks, pausing every now and then in an erect pose known as the UPRIGHT-AWARE POSTURE—the other male performs two displays. In the DART-GAPE, he pulls his head back and then darts it forward, at the same time opening his bill to expose the yellow interior and fanning his tail. In the THROW-BACK, he arches his neck along his back and points his beak upward while quivering his throat pouch. Sometimes the courting male will become aggressive and attack another male that approaches too closely, which also happens frequently when females approach courting males.

Frequency: Homosexual pairs and courtship occur only occasionally in these two species: no more than perhaps 1 in 500 pairs of Great Cormorants, for example, is composed of two males.

Orientation: Great Cormorants in homosexual pairs are sometimes sequentially bisexual, divorcing their male partners and going on to breed in heterosexual pairs. However, others re-pair with another male partner, and some homosexual pairs appear to last much longer, perhaps even for the birds’ lifetimes—in which case such individuals are exclusively (or extensively) homosexual for a significant part of their lives. Male European Shags that court other males are simultaneously bisexual, alternating heterosexual courtship with homosexual interactions (and probably a greater proportion of the former).

Several forms of nonprocreative sexual behavior are exhibited by these Cormorants. REVERSE mountings constitute 8 percent of European Shag heterosexual copulations (and also occur in Great Cormorants), while at least a quarter of all sexual activity takes place prior to the female’s fertilizable period. Great Cormorants sometimes copulate during the incubation period, while heterosexual copulations may continue even after Shag chicks have hatched. In a few cases, adult male Shags have been observed mating with their own chicks, and incestuous pairings sometimes also develop between brothers and sisters when they are still young. Nearly half of all heterosexual copulations in Shags involve mounting without genital contact, often because the female will not permit it. In addition, males are frequently hostile to females during the early phases of courtship (as noted above).

Nonmonogamous matings and courting of birds other than one’s partner occur in both of these species. In European Shags, for example, 14 percent of all copulations are promiscuous. Almost 18 percent of all chicks are fathered by a male other than their mother’s mate, but nearly 80 percent of all nonmonogamous matings are nonreproductive, taking place before females can be fertilized. At least 4 percent of all chicks are related to neither of the parents caring for them; this results from adoption and from females’ laying eggs in nests other than their own. About 3–5 percent of male Shags bond polygamously with two females; in addition, 30–40 percent of heterosexual Shag pairs divorce and re-pair with new mates the next season. Individuals may also change mates during the season. Some Shag parents are severely neglectful, refusing to feed their offspring, who may, as a result, die of starvation. In addition, about a third of all eggs lost through breakage result from interference by the females in polygamous associations. Finally, nonbreeding is a regular feature of some Shag populations: on average, 12–25 percent of all adults skip breeding at least once during their lifetime, and in some years as many as 60 percent of all birds forgo reproduction.

*asterisked references discuss homosexuality/transgender

Aebischer, N. J., G. R. Potts, and J. C. Coulson (1995) “Site and Mate Fidelity of Shags Phalacrocorax aristotelis at Two British Colonies.” Ibis 137:19–28.

Aebischer, N. J., and S. Wanless (1992) “Relationships Between Colony Size, Adult Non-Breeding, and Environmental Conditions for Shags Phalacrocorax aristotelis on the Isle of May, Scotland.” Bird Study 39:43–52.

*Fukuda, M. (1992) “Male-Male Pairing of the Great Cormorant (Phalacrocorax carbo hanedae).” Colonial Waterbird Society Bulletin 16:62–63.

Graves, J., R. T. Hay, M. Scallan, and S. Rowe (1992) “Extra-Pair Paternity in the Shag, Phalacrocorax aristotelis as Determined by DNA Fingerprinting.” Journal of Zoology, London 226:399–408.

Harris, M. P. (1982) “Promiscuity in the Shag as Shown by Time-Lapse Photography.” Bird Study 29:149–54.

Johnsgard, P. A. (1993) Cormorants, Darters, and Pelicans of the World. Washington and London: Smithsonian Institution Press.

*Kortlandt, A. (1995) “Patterns of Pair-Formation and Nest-Building in the European Cormorant, Phalacrocorax carbo sinensis.” Ardea 83:11–25.

*———(1949) “Textuur en structuur van het broedvoorbereidingsgedrag bij de aalscholver [Texture and Structure of Brooding-Preparatory Behavior in the Cormorant].” Ph.D. thesis, University of Amsterdam.

*Snow, B. K. (1963) “The Behavior of the Shag.” British Birds 56:77—103, 164—86.

Both of these species of Grebes commonly socialize in pairs or small groups, and sometimes in dense flocks (which may contain several thousand birds in Hoary-headed Grebes). They nest in large colonies—up to 400 nests for Hoary-headed Grebes—and most form monogamous pair-bonds.

Behavioral Expression: Male Silvery Grebes occasionally mount other males, using the same position as for heterosexual copulation—although unlike in heterosexual mating, the mounted bird does not typically invite the other male to mount him. In Hoary-headed Grebes, two birds of the same sex sometimes perform courtship displays to each other on floating platforms, constructed of water vegetation, and perhaps also mount one another. One such display is called REARING, in which the bird lifts its body up, ruffles its mantle feathers, and extends its head and neck downward. This may lead to one bird INVITING the other to mount, by settling back down, kinking its neck, and resting its throat on the nest.

Frequency: Same-sex activity occurs only occasionally in these two species of Grebes. In Silvery Grebes, for example, about 1 in 300 mounts is between two males.

Orientation: Grebes that participate in same-sex activities are probably bisexual, also courting and mating with members of the opposite sex.

In these two species of Grebes—as in many other Grebes—REVERSE heterosexual mountings are common. An average of 27 percent of all copulations among Silvery Grebes involve females mounting males, and early in the breeding season as many as 40 percent of all mounts are reverse. Their prevalence during this period—long before fertilization is possible—indicates that this form of behavior is decidedly nonprocreative. In addition, ejaculation does not usually occur during reverse mounts, although females typically perform tail thrusting, perhaps to facilitate genital contact. Grebes also copulate repeatedly, with as many as five or six matings taking place over 15–20 minutes; during this activity, males and females may also alternate positions in a form of reciprocal mounting. Although most heterosexual mating in Hoary-headed Grebes takes place between pair members, some copulations also occur between unpaired birds.

*asterisked references discuss homosexuality/transgender

*Fjeldså, J. (1983) “Social Behavior and Displays of the Hoary-headed Grebe Poliocephalus poliocephalus.” Emu 83:129–40.

Fjeldså, J. and N. Krabbe (1990) Birds of the High Andes. Copenhagen: Zoological Museum, University of Copenhagen; Svendborg, Denmark: Apollo Books.

Johnsgard, P. A. (1987) Diving Birds of North America. Lincoln and London: University of Nebraska Press.

*Nuechterlein, G. L., and R. W. Storer (1989) “Reverse Mounting in Grebes.” Condor 91:341—46.

*O‘Brien, R. M. (1990) “Hoary-headed Grebe, Poliocephalus poliocephalus.’ In S. Marchant and P. J. Higgins, eds., Handbook of Australian, New Zealand, and Antarctic Birds, vol. 1, pp. 100—107. Melbourne: Oxford University Press.

Storer, R. W. (1969) “The Behavior of the Horned Grebe in Spring.” Condor 71:180—205.

WADING BIRDS

Black-crowned Night Herons are fairly gregarious birds, gathering in colonies that may contain hundreds or thousands of individuals nesting close together. Monogamous pairs predominate during the mating season.

Behavioral Expression: Male Black-crowned Night Herons sometimes court other males and form homosexual pairs. To attract other birds, a male performs the SNAP-HISS CEREMONY, in which he repeatedly extends and lowers his head with erected plumes while “treading” with his feet and making a combined snapping (or clicking) and hissing sound. This courtship display is directed at both males and females. While most males are not interested in the ceremony, those that are attracted go on to participate in an OVERTURE display (also used in heterosexual courtship). In this activity, one or both males stretch their heads forward (again with feathers raised) while making their eyeballs protrude from their sockets, at the same time clicking and touching their bills. Males in homosexual pairs also mount each other (in the position used for heterosexual copulation); both males may mount or be mounted, although individuals sometimes show a preference for one or the other activity. Typically one male in the pair also builds a nest out of twigs; sometimes this occurs before the pair-bond forms, or else the two males may search for a nest site together. Once the pair-bond is established, both males vigorously defend their territory against other birds. Homosexual pair-bonds are strong, lasting the entire breeding season (as do heterosexual bonds). Young Black-crowned Night Herons also form pairs or “companionships,” some of which are between birds of the same sex (although no overt sexual behavior occurs between companions of either the same or opposite sex). Occasionally, a juvenile female may even bond with more than one other female. Although no homosexual pairs between adult females have yet been observed, females sometimes perform typically male courtship displays such as the snap-hiss ceremony.

Frequency: In some captive populations, homosexual pairs in adult males make up more than 20 percent of all pairings, while 38 percent of juvenile pairs are same-sex (three-quarters of which are between females). The incidence of same-sex pairs in the wild is not known. Adult male partners may mount each other more than 30 times over the mating season.

Orientation: During the courtship phase, males exhibit a form of simultaneous bisexuality by displaying to both sexes, and some males are clearly more attracted to same-sex courtships than others. Most young females that form same-sex bonds only pair with other females, while a few form both homosexual and heterosexual pair-bonds. Once a homosexual bond has formed, though, the birds will maintain the bond even if they are separated for several weeks, returning to their same-sex partner when reunited rather than establishing a heterosexual bond. Some birds may exhibit sequential bisexuality, forming heterosexual bonds after participating in homosexual pairings when young (or vice versa).

Male-female relations in Black-crowned Night Herons are sometimes fraught with complications. Heterosexual copulation is often incomplete because females refuse to cooperate in mating. In addition, in the early stages of courtship, males are often aggressive toward any bird that approaches them, including females. Chicks that hatch late are usually deserted by their parents after their siblings have fledged; they often move to other nests and are adopted by those families. Adults also occasionally accept eggs laid in their nest by other herons such as great egrets (Casmerodius albus) or lay their own eggs in nests of other species such as snowy egrets (Egretta thula).

*asterisked references discuss homosexuality/transgender

Allen, R. P., and F. P. Mangels (1940) “Studies of the Nesting Behavior of the Black-crowned Night Heron.” Proceedings of the Linnaean Society of New York 50–51:1–28.

Cannell, P. E, and B. A. Harrington (1984) “Interspecific Egg Dumping by a Great Egret and Black-crowned Night Herons.” Auk 101:889-91.

Davis, W. E., Jr. (1993) “Black-crowned Night Heron (Nycticorax nycticorax).” In A. Poole and F. Gill, eds., The Birds of North America: Life Histories for the 21 st Century, no. 74. Philadelphia: Academy of Natural Sciences; Washington, D.C.: American Ornithologists’ Union.

Gross, A. O. (1923) “The Black-crowned Night Heron (Nycticorax nycticorax naevius) of Sandy Neck.” Auk 40:1–30, 191–214.

Kazantzidis, S., V. Goutner, M. Pyrovetsi, and A. Sinis (1997) “Comparative Nest Site Selection and Breeding Success in 2 Sympatric Ardeids, Black-Crowned Night-Heron (Nycticorax nycticorax) and Little Egret (Egretta garzetta) in the Axios Delta, Macedonia, Greece.” Colonial Waterbirds 20:505–17.

*Lorenz, K. (1938) “A Contribution to the Comparative Sociology of Colonial-Nesting Birds.” In F. C. R. Jourdain, ed., Proceedings of the Eighth International Ornithological Congress, Oxford (July 1934), pp. 207–21. Oxford: Oxford University Press.

McClure, H. E., M. Yoshii, Y. Okada, and W. F. Scherer (1959) “A Method for Determining Age of Nestling Herons in Japan.” Condor 61:30–37.

*Noble, G. K., and M. Wurm (1942) “Further Analysis of the Social Behavior of the Black-crowned Night Heron.” Auk 59:205–24.

*Noble, G. K., M. Wurm, and A. Schmidt (1938) “Social Behavior of the Black-crowned Night Heron.” Auk 55:7–40.

Schorger, A. W. S. (1962) “Black-crowned Night Heron.” In R. S. Palmer, ed., Handbook of North American Birds, vol. 1: Loons through Flamingos, pp. 472–84. New Haven and London: Yale University Press.

Herons and Egrets are highly social birds, nesting in dense colonies that may include birds of several different species. During the mating season the primary social unit is the monogamous pair, although several alternative mating systems occur (see below). Outside of the breeding season, they may be found either singly or in flocks.

Behavioral Expression: In all four of these Heron and Egret species, males that are paired to females often copulate with birds other than their mates; in some cases, these involve homosexual copulations with other males who are themselves also paired to females. Homosexual mountings always take place during the mating season. In Little Egrets, mountings between males are most common during the early stages of heterosexual pair formation (before nest-building begins), while in Little Blue Herons at least some homosexual activity takes place during the incubation period, since males have been seen mounting other males that are sitting on eggs. Typically, males mount birds in neighboring nests, although in Little Egrets and Little Blue Herons males may travel to other areas of the breeding colony to engage in “extramarital” or promiscuous copulations (both homosexual and heterosexual).

In Cattle Egrets (and probably the other species as well), homosexual mountings always take place on the mountee’s nest. In a typical encounter, the male seeking an “extramarital” liaison approaches another male, uttering RICK RACK calls (a harsh double croaking sound, also used in heterosexual encounters). The first male then mounts the other bird and crouches on his back; some males only act as mounters in homosexual copulations, others only as mountees, while some males perform both roles. In Little Blue Herons and Cattle Egrets, homosexual mountings may also occur when one male mounts another male who is himself attempting to copulate with a female; sometimes, “pile-ups” of three or four males on top of each other may develop in this way. Usually the mountee is aggressive toward the male mounting him and does not permit cloacal contact. Similarly, male-female “extramarital” copulations are rarely completed, owing to resistance by the female or defense by her mate. In Cattle Egrets, nearly a quarter of all such heterosexual mounting attempts do not involve cloacal contact, while in Little Egrets more than 85 percent of such opposite-sex copulations are “incomplete.”

Frequency: Homosexual mountings can be quite common: in Little Egrets, for example, more than 100 mounts between males were recorded over four months in one colony, with such copulations comprising 5—6 percent of all “extramarital” sexual activity. In Little Blue Herons, homosexual mountings make up 3—6 percent of all copulations outside the pair-bond. Mounts between males represent 5 percent of “extramarital” copulations and 3 percent of all copulations in Cattle Egrets, while in Gray Herons they constitute 8 percent of all promiscuous mountings and 1 percent of the total number of copulations. In 18 percent of “extramarital” copulation attempts on female Cattle Egrets, additional males mount other males in a pile-up.

Orientation: Since males that participate in homosexual activity almost always have female mates, they are technically bisexual (and some birds may even participate in “group” sexual activity involving both males and females simultaneously, as in Little Blue Herons). In Little Egrets, about one-quarter of the male population engages in homosexual mounting, in Gray Herons 5—7 percent of males are involved in such activity, while in Cattle Egrets six out of ten males in one colony participated in same-sex mounting. Some individuals seem to show more of a “predilection” for homosexual behavior than others. In Cattle Egrets, for example, certain males engage in “extramarital” mountings only with males rather than females, while in both this species and in Little Egrets, some individuals participate in same-sex activity noticeably more often than others. In addition, homosexual activity comprises a greater proportion of “extramarital” sexual activity for some males than for others.

As described above, “extramarital” or promiscuous heterosexual copulations occur commonly in all four of these species. In Cattle Egrets, as many as 60 percent of all mountings are by males on females other than their mates, while in Gray Herons such matings account for more than 12 percent of all sexual activity. Nearly a third of all Little Egret copulations are promiscuous. In fact, many copulations in this context are actually rapes, since the female is not a willing participant (although in both Cattle and Little Egrets, females may also consent to such matings). Up to 7 percent of Cattle Egret eggs may be fertilized by a male other than the bird’s (social) father; however, many “extramarital” copulations are nonprocreative, since almost a quarter of all such matings take place when the female is already incubating her eggs. In addition to stepparenting of birds fathered by other males, several other alternative family arrangements occur: Cattle Egret trios of two females and one male may raise a family, while foster-parenting sometimes occurs when females lay their eggs in nests of other birds, including other species of Egrets and Herons.

Several mating behaviors in these species indicate that not all aspects of heterosexuality revolve around breeding. Cattle Egrets sometimes mate when fertilization is not possible, for example during incubation or chick-raising. And up to 14 percent of copulations between pair members may be “incomplete” in the sense that no genital contact or sperm transfer occurs—sometimes because the male is apparently not “interested” in mating even though his female partner is. In Little Blue Herons, some males copulate with females and yet remain “single” (i.e., do not pair-bond with them), while other males never pair with a female during the entire mating season. REVERSE mounts (females mounting males) also occur in Cattle Egrets, and in polygamous trios this sometimes results in a “pile-up” of three birds (one female mounting the second female who is mounting the male).

A number of violent and counterreproductive behaviors can make life harsh for young Egrets and Herons. In Little Blue Herons, infidelity often leads to abandonment of the nest by one or both partners (in part because eggs may be broken during the promiscuous sexual activity). Following a partner’s injury, male Cattle Egrets have been known to destroy their own eggs and desert their mates for a new female. Male Gray Herons also occasionally destroy their eggs by stabbing at them. Nest and mate desertion (especially by females) are common in Little Egrets as well. Often the remaining bird will successfully raise the chicks as a single parent; sometimes, though, the chicks die as a result of desertion. If a single father pairs with a new female, she may kill his nestlings by pecking them to death, so that she can mate with him and raise her own offspring. Cannibalism by siblings or parents sometimes occurs in Gray Herons. In addition, Heron and Egret families are often systematically “pared down” because the youngest nestlings starve to death when they are unable to compete for food; more than three-quarters of all nestling deaths in Little Blue Herons are the result of such “brood reduction.”

*asterisked references discuss homosexuality/transgender

Blaker, D. (1969) “Behavior of the Cattle Egret Ardeola ibis.” Ostrich 40:75-129.

*Fujioka, M. (1996) Personal communication.

———(1989) “Mate and Nestling Desertion in Colonial Little Egrets.” Auk 106:292-302.

*———(1988) “Extrapair Copulations in Little Egrets (Egretta garzetta).” Paper presented at the annual meeting of the Animal Behavior Society, University of Montana.

———(1986a) “Infanticide by a Male Parent and by a New Female Mate in Colonial Egrets.” Auk 103:619—21.

———(1986b) “Two Cases of Bigyny in the Cattle Egret Bubulcus ibis.” Ibis 128:419—22.

———(1985) “Sibling Competition and Siblicide in Asynchronously-Hatching Broods of the Cattle Egret Bubulcus ibis.” Animal Behavior 33:1228-42.

*Fujioka, M., and S. Yamagishi (1981) “Extramarital and Pair Copulations in the Cattle Egret.” Auk 98:134—44.

Lancaster, D. A. (1970) “Breeding Behavior of the Cattle Egret in Colombia.” Living Bird 9:167-94.

McKilligan, N. G. (1990) “Promiscuity in the Cattle Egret (Bubulcus ibis) Auk 107:334—41.

*Meanley, B. (1955) “A Nesting Study of the Little Blue Heron in Eastern Arkansas.” Wilson Bulletin 67:84—99.

Milstein, P. le S., I. Prestt, and A. A. Bell (1970) “The Breeding Cycle of the Gray Heron.” Ardea 58:171-257.

*Ramo, C. (1993) “Extra-Pair Copulations of Gray Herons Nesting at High Densities.” Ardea 81:115-20.

Rodgers, J. A., Jr. (1980a) “Little Blue Heron Breeding Behavior.” Auk 97:371—84.

———(1980b) “Breeding Ecology of the Little Blue Heron on the West Coast of Florida.” Condor 82:164—69.

Rodgers, J. A., Jr., and H. T. Smith (1995) “Little Blue Heron (Egretta caerulea).” In A. Poole and F. Gill, eds., The Birds of North America: Life Histories for the 21st Century, no. 145. Philadelphia: Academy of Natural Sciences; Washington, D.C.: American Ornithologists’ Union.

Telfair, R. C., II (1994) “Cattle Egret (Bubulcus ibis).” In A. Poole and F. Gill, eds., The Birds of North America: Life Histories for the 21st Century, no. 113. Philadelphia: Academy of Natural Sciences; Washington, D.C.: American Ornithologists’ Union.

*Werschkul, D. F. (1982) “Nesting Ecology of the Little Blue Heron: Promiscuous Behavior.” Condor 84:381—84.

———(1979) “Nestling Mortality and the Adaptive Significance of Early Locomotion in the Little Blue Heron.” Auk 96:116—30.

Pukeko are notable for their “communal” breeding system: they form stable groups of 4–14 birds during the mating season, usually with an equal number of males and females. All adult members (except nonbreeding “helpers,” see below) generally mate with each other, and both sexes take turns incubating the eggs, which are often laid by several females in the same nest. Some birds pair off into (heterosexual) couples or remain single rather than forming communal groups, and outside the breeding season Pukeko usually live in flocks. Many Tasmanian Native Hens and Dusky Moorhens also live in (generally smaller) communal breeding groups that have various types of polygamous or promiscuous mating arrangements. Some Tasmanian Native Hens also form monogamous pair-bonds.

Behavioral Expression: Both male and female Pukeko engage in homosexual courtship and copulation with members of their communal group; these activities are more common and more developed between female birds. Lesbian courtship consists of a sequence of three activities (which also occur during heterosexual interactions). The courtship begins with ALLOPREENING: one female approaches another and bows to her, initiating mutual preening (stylized stroking of each other’s feathers with their bill). This is followed by COURTSHIP-FEEDING, in which the two females exchange ritual gifts of food (usually small leaves or shoots). Finally, copulation takes place: the courting bird approaches the other in a distinctive upright posture while making a nasal HUMMING CALL; her partner adopts a hunched posture and mounting takes place, often with full cloacal (genital) contact. Sometimes, the two females reciprocate, the bird who was mounted first then mounting the other. Male homosexuality usually involves copulation and sometimes allopreening, but not courtship-feeding. Unlike female same-sex interactions, sexual activity between males is often initiated by the bird that is mounted, who places himself in the hunched posture in front of the other male as an invitation to mount.

In Tasmanian Native Hens, homosexual copulations occur in both males (often younger birds) and females living in the same group, while only male Dusky Moorhens participate in same-sex mounting. In all three species, birds that engage in homosexual activities also undertake parental duties such as nest-building, egg laying, incubation, and care of chicks (whether their own or those of other members of their communal group). In fact, homosexual activity (like heterosexual activity) in female Pukeko is most frequent just before or during the period of egg laying. Because birds in Pukeko and Tasmanian Native Hen groups are often related to each other, at least some homosexual—as well as heterosexual—activity is incestuous (mostly between brothers in Tasmanian Native Hens).

Frequency: Homosexuality is common among Pukeko, occurring in nearly 45 percent of all communal groups. In this species, 7 percent of all copulations are homosexual, while 24 percent of courtship-feedings and 59 percent of courtship allopreening interactions are same-sex. In Tasmanian Native Hens and Dusky Moorhens, homosexual copulations make up 1—2 percent of all matings.

Orientation: Many adult breeding Pukeko are probably bisexual, capable of engaging in both homosexual and heterosexual courtship and copulation. In some cases, birds alternate between same-sex and opposite-sex copulations in quick succession. Nonbreeding helpers, however, generally participate in neither heterosexual nor homosexual activity. Far fewer individuals participate in homosexual behavior in Tasmanian Native Hens and Dusky Moorhens, but those that do are probably also bisexual.

As described above, the most common social unit among these species of Rails is not the heterosexual pair or nuclear family, but the communal group. In some populations of Pukeko, each such group may include up to seven nonbreeding individuals who assist in parental duties. These “helpers” (offspring from previous years) may delay their own reproductive careers for up to three years (one or two years in Tasmanian Native Hens, where an average of 18 percent of adults are nonbreeders). Some physiological mechanisms may be involved in this breeding suppression, since Pukeko helpers often have underdeveloped reproductive organs. In addition to several forms of polygamy, a number of other mating and parenting arrangements are found in these groups. For example, although all birds in Tasmanian Native Hen groups usually mate with each other, sometimes only one male-female pair actually has reproductive copulations. This social system has been called GENETIC MONOGAMY (because only one couple breeds) within SOCIAL POLYGAMY (since multiple partners mate with each other). In addition, although most group members remain together for life, females occasionally “divorce” their mates and join a new group; in some cases, this may lead to a female parenting young that are not her own. Occasionally, she may behave aggressively toward these foster chicks, even expelling them from the group. More violent confrontations sometimes occur when chicks stray into neighboring territories, where they may be killed by the resident group members. However, chicks are sometimes also adopted by neighboring groups, in both Tasmanian Native Hens and Dusky Moorhens.

Among breeding Pukeko, up to five males may court and mount the same female in quick succession—in these cases, one or more of the males may not actually inseminate the female. In fact, the “success” rate for most heterosexual copulations is not high: between one-half and two-thirds do not involve full genital contact and so do not result in insemination. Females often resist heterosexual advances by refusing to allow males to mount them, pecking at males who do mount them, preventing genital contact by not raising their tails, and prematurely terminating mating attempts. Copulations also occur when females are not fertile—for example, long before egg laying begins—and some males mate repeatedly without ever fathering any offspring that year. Similarly, mounts without genital contact account for more than a third of Dusky Moorhen matings and 60 percent of Tasmanian Native Hen matings. A few of these are REVERSE copulations, in which the female mounts the male. Incestuous matings are also common in Pukeko and Tasmanian Native Hens. Nearly two-thirds of all Pukeko heterosexual copulations in some populations are between related individuals, including mother-son, father-daughter, and brother-sister matings. More than 40 percent of Tasmanian Native Hen breeding groups contain related adults that mate with each other (mostly siblings); in addition, about 10 percent of copulations involve parents mounting their own offspring, including young chicks.

Stable homosexual pairs often form among Cranes (e.g., Grus spp.) in captivity, a group of birds that is closely related to Rails.

*asterisked references discuss homosexuality/transgender

*Archibald, G. W. (1974) “Methods for Breeding and Rearing Cranes in Captivity.” International Zoo Yearbook 14:147-55.

Craig, J. L. (1990) “Pukeko: Different Approaches and Some Different Answers.” In P. B. Stacey and W. D. Koenig, eds., Cooperative Breeding in Birds: Long-term Studies of Ecology and Behavior, pp. 385-412. Cambridge: Cambridge University Press.

*———(1980) “Pair and Group Breeding Behavior of a Communal Gallinule, the Pukeko, Porphyrio p. melanotus.” Animal Behavior 28:593-603.

———(1977) “The Behavior of the Pukeko.” New Zealand Journal of Zoology 4:413—33.

Craig, J. L., and I. G. Jamieson (1988) “Incestuous Mating in a Communal Bird: A Family Affair.” American Naturalist 131:58-70.

*Derrickson, S. R., and J. W. Carpenter (1987) “Behavioral Management of Captive Cranes—Factors Influencing Propagation and Reintroduction.” In G. W. Archibald and R. F. Pasquier, eds., Proceedings of the 1983 International Crane Workshop, pp. 493—511. Baraboo, Wis.: International Crane Foundation.

Garnett, S. T. (1980) “The Social Organization of the Dusky Moorhen, Gallinula tenebrosa Gould (Aves: Rallidae).” Australian Wildlife Research 7:103-12.

*———(1978) “The Behavior Patterns of the Dusky Moorhen, Gallinula tenebrosa Gould (Aves: Rallidae).” Australian Wildlife Research 5:363-84.

Gibbs, H. L., A. W. Goldizen, C. Bullough, and A. R. Goldizen (1994) “Parentage Analysis of Multi-Male Social Groups of Tasmanian Native Hens (Tribonyx mortierii): Genetic Evidence for Monogamy and Polyandry.” Behavioral Ecology and Sociobiology 35:363—71.

Goldizen, A. W., A. R. Goldizen, and T. Devlin (1993) “Unstable Social Structure Associated with a Population Crash in the Tasmanian Native Hen, Tribonyx mortierii.” Animal Behavior 46:1013-16.

Goldizen, A. W., A. R. Goldizen, D. A. Putland, D. M. Lambert, C. D. Millar, and J. C. Buchan (1998) “‘Wife-sharing’ in the Tasmanian Native Hen (Gallinula mortierii): Is It Caused By a Male-biased Sex Ratio?” Auk 115:528—32.

*Jamieson, I. G., and J. L. Craig (1987a) “Male-Male and Female-Female Courtship and Copulation Behavior in a Communally Breeding Bird.” Animal Behavior 35:1251-53.

———(1987b) “Dominance and Mating in a Communal Polygynandrous Bird: Cooperation or Indifference Towards Mating Competitors?” Ethology 75:317-27.

Jamieson, I. G., J. S. Quinn, P. A. Rose, and B. N. White (1994) “Shared Paternity Among Non-Relatives Is a Result of an Egalitarian Mating System in a Communally Breeding Bird, the Pukeko.” Proceedings of the Royal Society of London, Series B 257:271-77.

*Lambert, D. M., C. D. Millar, K. Jack, S. Anderson, and J. L. Craig (1994) “Single- and Multilocus DNA Fingerprinting of Communally Breeding Pukeko: Do Copulations or Dominance Ensure Reproductive Success?” Proceedings of the National Academy of Sciences 91:9641—45.

*Ridpath, M. G. (1993) “Tasmanian Native-hen, Tribonyx mortierii.” In S. Marchant and P. J. Higgins, eds., Handbook of Australian, New Zealand, and Antarctic Birds, vol. 2, pp. 615—24. Melbourne: Oxford University Press.

*———(1972) “The Tasmanian Native Hen, Tribonyx mortierii. I. Patterns of Behavior. II. The Individual, the Group, and the Population.” CSIRO Wildlife Research 17:1—90.

*Swengel, S. R., G. W. Archibald, D. H. Ellis, and D. G. Smith (1996) “Behavior Management.” In D. H. Ellis, G. F. Gee, and C. M. Mirande, eds., Cranes: Their Biology, Husbandry, and Conservation, pp. 105—22. Washington, D.C.: National Biological Service; Baraboo, Wis.: International Crane Foundation.

Hammerheads are usually found in pairs or groups of 8–10 individuals, though larger groups of up to 50 birds may also congregate. The mating system is believed to involve monogamous pair-bonds. Couples build extraordinarily large domed nests, often several on the same territory.

Behavioral Expression: Hammerheads engage in a striking group courtship ceremony that includes same-sex mounting. Gathering at dawn on open lawns, riverbanks, rocks, or in the trees, groups of 3—20 birds (including some mated pairs) begin calling in unison. Their calls consist of a series of loud, high-toned yips that develop into a rapid sequence of “purring” or trilling notes, often accompanied by wing-flapping. Two or more birds may then perform a NODDING DISPLAY to each other, in which the bill is rapidly bobbed up and down (sometimes still accompanied by the YIP-PURR chorus), or pairs of birds may run in circles side by side. The culmination of this spectacular display is a series of mountings, initiated when one bird runs up to another, drooping and flicking its wings while it raises and lowers its crest, or when one bird solicits another by crouching, cocking its tail, and partially opening its wings. One Hammerhead then hops onto the back of the other, similar to a heterosexual copulation—except that, in addition to males mounting females, males also mount other males, and females mount females as well as males. The mounting bird beats its wings and gives the YIP-PURR call, while the mounted bird presses its tail up against the lowered tail of the mounter (though no cloacal [genital] contact takes place). Sometimes the two birds face in opposite directions; reciprocal mounting (mounter and mountee exchanging positions, often several times in succession) also occurs, as do “pile-ups” of three or four birds all mounted on each other.

Frequency: Social courtship displays including ritualized same-sex mounting occur commonly in Hammerheads throughout the year. Each mounting session lasts for 10—40 minutes and may include dozens of mountings.

Orientation: All Hammerheads participate in group courtship displays, and most birds are probably involved in both same-sex and opposite-sex mountings.

As noted above, nonprocreative heterosexual activity (REVERSE mounting, as well as male-female mounts without cloacal contact) is common in Hammerheads. In addition, a significant percentage of heterosexual pairs may be nonbreeders. In some populations, as many as three-quarters of nests go unused (although some of these are “extra” nests built by breeding pairs), and couples may forgo breeding for four or more years at a time.

Same-sex pairing occurs in semiwild White Storks (Ciconia ciconia) in some European populations, and individuals form homosexual pairs even when numerous opposite-sex partners are available. Same-sex pairs are able to successfully incubate, hatch, and raise foster young.

*asterisked references discuss homosexuality/transgender

*Brown, L. H. (1982) “Scopidae, Hamerkop.” In L. H. Brown, E. K. Urban, and K. Newman, eds., The Birds of Africa, vol. 1, pp. 168—72. London and New York: Academic Press.

*Campbell, K. (1983) “Hammerkops.” E.A.N.H.S. (East Africa Natural History Society) Bulletin (January-April): 11. 1.

Cheke, A. S. (1968) “Copulation in the Hammerkop Scopus umbretta.” Ibis 110:201—3.

*Elliott, A. (1992) “Scopidae (Hamerkop).” In J. del Hoyo, A. Elliott, and J. Sargatal, eds., Handbook of the Birds of the World, vol. 1, Ostrich to Ducks, pp. 430—35. Barcelona: Lynx Edicións.

Goodfellow, C. F. (1958) “Display in the Hamerkop, Scopus umbretta.” Ostrich 29:1—4.

Kahl, M. P. (1967) “Observations on the Behavior of the Hamerkop Scopus umbretta in Uganda.” Ibis 109:25—32.

*King, C. E. (1990) “Reproductive Management of the Oriental White Stork Ciconia boyciana in Captivity.” International Zoo Yearbook 29:85—90.

Stowell, R. F. (1954) “A Note on the Behavior of Scopus umbretta.” Ibis 96:150—51.

Wilson, R. T., and M. P. Wilson (1984) “Breeding Biology of the Hamerkop in Central Mali.” In J. Ledger, ed., Proceedings of the 5th Pan-African Ornithological Congress, pp. 855—65. Johannesburg: Southern African Ornithological Society.

Flamingos are extremely gregarious birds, often congregating in enormous groups numbering in the tens of thousands. During the mating season pair-bonds are formed and the birds nest in large colonies.

Behavioral Expression: Flamingos form both male and female homosexual pairs. The bond is similar to that of a heterosexual mated pair and is expressed through shared activities, such as feeding and traveling together, calling in unison, helping each other in aggressive encounters against other birds, and sleeping side by side. The pair-bond is also reinforced through a number of stylized displays, such as ritual preening and feeding, as well as standing in an alert posture (with a graceful S-curve in the neck) in front of each other. Partners may even engage in mounting and copulations with one another; full genital contact occurs in matings between females, but not usually between males. Early in the breeding season, single male Flamingos also sometimes pursue other males in an attempt to mount them; this is known as DRIVING. Single males seeking male partners have even been known to harass heterosexual pairs, following them around and disrupting their copulations and incubation shifts in an attempt to gain access to the male.

Once formed, homosexual pair-bonds are strong and may persist from one breeding season to the next. Most pairings are monogamous; however, in some male pairs the partners also attempt to mount other birds (usually incubating birds of either sex). Sometimes two males and a female will even form a TRIAD in which the two males are bonded or sexually interested in each other as much, if not more so, than they are in the female. Homosexual partners sometimes also build nests together; in the case of male pairs, the nest (a pedestal-shaped mud platform) may become exceptionally large because of the contributions of both partners. Some male pairs, rather than building their own nest, “steal” or take over the nest of a heterosexual pair, occasionally breaking eggs in the process (this behavior also occurs between heterosexual pairs).

Homosexual couples often engage in parenting behavior. Male pairs incubate, hatch, and successfully raise foster chicks (for example, from a nest they have taken over, or from eggs supplied in captivity). Described as “model” parents, male partners may even “nurse” their chick. Flamingo parents (of either sex) typically feed their chicks a blood-red “milk” produced in their crops, and both males in homosexual couples feed their chicks with this crop milk. Some male pairs, however, do not attempt to acquire eggs, even if they have their own nest, while others do not appear to be interested in parenting at all, since they may roll the egg out of a nest they have acquired. Female pairs take turns incubating eggs on their nest; such eggs may be infertile, having been laid by the females themselves rather than acquired from another nest. As in heterosexual pairs, variation exists in the amount of incubation time contributed by each partner. Some share incubation duties equally, while in other pairs, one female puts in more incubation shifts than the other. Overall, though, females in lesbian pairs contribute about five to six incubation shifts each, which is comparable to the average for heterosexual partners.

Frequency. In most captive populations with same-sex couples, about 5–6 percent of pairs are homosexual, although some populations have more than a quarter same-sex couples. Although homosexual pairs have not yet been observed in the wild, oversize nests similar to those built by male pairs are found in most colonies and may in fact belong to homosexual pairs (especially considering that most field studies have not systematically and unambiguously determined the sexes of all paired birds).

Orientation: Overall, only a fraction of the population is involved in same-sex pairing. Among these, some individuals have no prior heterosexual experience. However, other Flamingos in homosexual pairs were previously members of a heterosexual pair (and vice versa). Some males in same-sex pairs also occasionally attempt to mount other birds, including females. These are both examples of different types of bisexuality (sequential and simultaneous). In populations with more males than females (or vice versa), many birds remain single rather than forming same-sex pair-bonds, perhaps indicating more of a heterosexual orientation on their part.

Although the standard social unit in Flamingos is the breeding monogamous pair, a number of alternative heterosexual pairing and family arrangements occur. Trios or triads—one male with two females or one female with two males—are fairly common (at least in zoos). Typically all three birds share incubation and chick-raising duties (although no same-sex bonding occurs); in trios with two females, there may be two separate nests, or both females may share a nest. Flamingo pairs also sometimes engage in nonreproductive copulations, mating far in advance of the female’s fertile (or the male’s sperm-producing) period. Many mated pairs are nonmonogamous, with both males and females seeking copulations with outside partners. In one zoo population, 47 percent of the females and 79 percent of the males participated in such “infidelity,” and about 8 percent of all copulations were with outside partners; at another zoo, 25—60 percent of all pairs were nonmonogamous. Furthermore, divorce is extremely common in wild Flamingos: nearly all birds change partners between breeding seasons, and about 30 percent of males even switch mates during the season (in contrast, most pairings in zoos are long-lived).

Once chicks are hatched, a number of social systems are available to relieve the biological mother and father of some of their parenting duties. For example, nonbreeding birds sometimes produce crop milk and “nurse” other birds’ chicks or else act as foster feeders for orphaned chicks. In addition, as they get older, Flamingo chicks typically gather into large nursery groups or CRÈCHES, which may contain several thousand youngsters. These groups provide them with safety in the absence of direct parental supervision, and adults also sometimes feed youngsters other than their own in these crèches. Chicks are often forced into crèches as a result of attacks from adult birds, including their own parents, and crèches may therefore also provide refuge from aggression by other Flamingos. Breeding in wild Flamingos can be irregular, with entire colonies sometimes forgoing reproduction for three or four years at a time—one colony in France failed to produce chicks for 13 out of 34 years (38 percent of the time). In addition, even if breeding is undertaken, it may be abruptly halted, with all or a large portion of the colony—often as many as half of all pairs—abandoning their eggs. Usually it is the female who initiates desertion of a nest.

Homosexual pairs occur among both male and female Lesser Flamingos (Phoeniconaias minor) in captivity, including nest-building and (in females) egg-laying. Both sexes participate in homosexual mounting, though only males generally achieve full genital contact. Males in same-sex pairs also sometimes chase and mount females in lesbian pairs, while the latter may mate with males to fertilize their eggs. Most females in homosexual pairs, however, show no interest in males. Pairs of female Scarlet Ibises (Eudocimus ruber) have also been observed in captive flocks, nesting together and sometimes laying fertile eggs.

*asterisked references discuss homosexuality/transgender

Allen, R. P. (1956) The Flamingos: Their Life History and Survival. National Audubon Society Research Report no. 5. New York: National Audubon Society.

*Alraun, R., and N. Hewston (1997) “Breeding the Lesser Flamingo Phoeniconaias minor,” Avicultural Magazine 103:175—81.

Bildstein, K. L., C. B. Golden, and B. J. McCraith (1993) “Feeding Behavior, Aggression, and the Conservation Biology of Flamingos: Integrating Studies of Captive and Free-Ranging Birds.” American Zoologist 33:117—25.

Cézilly, F. (1993) “Nest Desertion in the Greater Flamingo, Phoenicopterus ruber roseus.” Animal Behavior 45:1038—40.

Cézilly, F., and A. R. Johnson (1995) “Re-Mating Between and Within Breeding Seasons in the Greater Flamingo Phoenicopterus ruber roseus.” Ibis 137:543-46.

*Elbin, S. B., and A. M. Lyles (1994) “Managing Colonial Waterbirds: the Scarlet Ibis Eudocimus ruber as a Model Species.” International Zoo Yearbook 33:85-94.

Kahl, M. P. (1974) “Ritualized Displays.” In J. Kear and N. Duplaix-Hall, eds., Flamingos, pp. 142-49. Berkhamsted, UK: T. and A. D. Poyser.

*King, C. E. (1996) Personal communication.

*———(1994) “Management and Research Implications of Selected Behaviors in a Mixed Colony of Flamingos at Rotterdam Zoo.” International Zoo Yearbook 33:103-13.

*———(1993a) “Ondergeschoven Kinderen [Supposititious Children].” Dieren 10(4):116—19.

*———(1993b) “Ongelukkige Flamingo Liefdes [Tales of Flamingo-Love Gone Awry].” Dieren 10(2):36—39.

Ogilvie, M., and C. Ogilvie (1989) Flamingos. Wolfeboro, N.H.: Alan Sutton.

*Shannon, P. (1985) “Flamingo Management at Audubon Park Zoo and the Benefits of Long-Term Research.” In AAZPA Regional Conference Proceedings, pp. 226—36. Wheeling, W.Va.: AAZPA.

*Stevens, E. F. (1996) Personal communication.

———(1991) “Flamingo Breeding: The Role of Group Displays.” Zoo Biology 10:53—63.

*Studer-Thiersch, A. (1975) “Basle Zoo.” In Kear and Duplaix-Hall, Flamingos, pp. 121—30.

Tourenq, C., A. R. Johnson, and A. Gallo (1995) “Adult Aggressiveness and Crèching Behavior in the Greater Flamingo, Phoenicopterus ruber roseus.” Colonial Waterbirds 18:216—21.

*Wilkinson, R. (1989) “Breeding and Management of Flamingos at Chester Zoo.” Avicultural Magazine 95:51-61.

SANDPIPERS AND THEIR RELATIVES

Ruffs and Buff-breasted Sandpipers are both LEKKING species, which means that males gather together to perform elaborate courtship displays on communal grounds known as LEKS (some Buff-breasts also display solitarily). The mating system is polygamous or promiscuous: males (and sometimes females) mate with multiple partners, and females raise any resulting offspring on their own. Outside of the breeding season these sandpipers tend to associate in flocks, which can number in the thousands among Ruffs.

Behavioral Expression: There are four distinct types or “classes” of male Ruffs, differing in their appearance, social behavior, and sexuality. RESIDENT males generally have dark plumage (with a wide variety of different feather patterns) and defend their own territories on the lek. MARGINAL males look similar to residents but do not have their own territories; they stay on the periphery of the lek and are often attacked by residents. SATELLITE males usually have white or light-colored plumage; they do not own territories, but often visit the lek and associate with particular residents. Finally, NAKED-NAPE males lack the nuptial plumage—ruff and head tufts—of other males, giving them the superficial appearance of females. They are not territorial either, but occasionally visit leks for short periods. Naked-napes may include younger males and/or adults passing through on their migratory journeys prior to developing their breeding plumage. Resident and satellite males also differ genetically from one another.

Homosexual behavior occurs among males of all types and is especially prominent between residents and satellites. While a resident male is displaying on his territory, one or more satellites may approach him and engage in courtship behaviors. Most notable of these is SQUATTING, in which the males lie with their bellies to the ground and expand their ruffs, crouching together while the resident places his bill on top of the satellite’s head. This may lead to homosexual copulation, in which either the resident or the satellite mounts the other male and attempts to make genital contact—he lowers himself and spreads his wings while holding the other male’s head feathers in his bill. The mounted bird reacts by either remaining crouched or by trying to shake the other male off his back. If more than one satellite male is present on the lek, they sometimes also mount each other. Many satellites have “preferred” resident males with whom they spend most of their time, and residents may also actively entice satellite males onto their display courts.

Females are often drawn to the activities between resident and satellite males, and heterosexual courtship and copulation (involving either residents or satellites) may occur at the same time as homosexual activities (or shortly thereafter). Occasionally, a satellite male will mount a resident male who is in the act of mating with a female; residents and satellites may also try to prevent each other from mating with females. Naked-nape males also engage in homosexual mounting with each other and with residents. When a naked-nape arrives on the lek, the resident male may respond by squatting; the naked-nape approaches him in a horizontal posture or may himself squat. The naked-nape may then try to mount the resident, although he does not usually lower his body to “complete” the copulation; he may also mount in a backwards position with his head facing the resident’s tail. Residents also sometimes mount naked-napes, and naked-napes also mount each other. Naked-nape males are sometimes courted by other males during stopovers on the spring migration as well (i.e., outside of the mating season). Although marginal males rarely participate in sexual activity (with either males or females), they have occasionally been seen mounting other males.

Female Ruffs—also known as Reeves—engage in homosexual behavior as well. They often arrive on a lek in groups, and females sometimes mount one another as they begin simultaneously crouching near a resident male during courtship activities. Genital contact may occur, although this is difficult to verify, even for heterosexual (or male homosexual) copulations. Females also occasionally court each other, using some of the same stylized movements such as wing quivering that are seen in heterosexual courtship.

Male Buff-breasted Sandpipers attract other birds to their lek territories with a dramatic WING-UP DISPLAY that can be seen from miles away, in which they raise one wing vertically and flash its brilliant satiny-white underlining. Usually females are attracted to this courtship display, and sometimes up to six of them gather around a displaying male. Often, however, a male from a neighboring territory is drawn to the display as well (or he may “camouflage” himself in a group of females). He may interrupt the courtship when he arrives by mounting the displaying male and trying to copulate with him. He may also aggressively peck the other male on his head and neck while mounted on him, then fly back to his own territory. Sometimes the females follow him, and then the pattern of interruption and mounting is repeated, only this time the other male arrives to disrupt the courtship. This sequence of heterosexual courtship and homosexual mounting may be repeated many times, back and forth for an hour or more. Sometimes, instead of flying back to his own territory with the females, a male simply returns repeatedly to his neighbor’s territory, continuously interrupting the male’s courtship by mounting him. Homosexual mounting also occurs in other contexts: when not as many females are present on the leks (especially later in the mating season), one or more males may enter a neighbor’s territory and simply mount him. As many as four males at a time may participate in such activity.

Frequency: Homosexual mounting occurs regularly in Ruffs, especially at the beginning of the mating season. During one informal three-and-a-half-hour observation period, for example, 3 out of 12 mountings (25 percent) were between males. In Buff-breasted Sandpipers, courtship interruptions by other males are common. Nearly a third of all courtships are disrupted by another male’s arrival, although homosexual mounting does not necessarily take place every time—but then neither does heterosexual mounting, since females usually leave without having copulated (even if there has been no interruption).

Orientation: In Ruffs, homosexual behavior is seen primarily in resident males, who constitute about 40 percent of the male population, and satellite males, who make up roughly 15 percent to one-third of all males (on average). Not all of these individuals engage in same-sex mounting—but neither do they all participate in heterosexual mounting. On some leks, just over half the resident males mate with females—and some only copulate once each season—while 40—90 percent of satellites never mate with females (although they may court them). Of those birds that do participate in homosexual behavior, many alternate between same-sex and opposite-sex interactions and are therefore bisexual. This is also true of females, although some Reeves seem to “prefer” homosexual interactions since they ignore males in favor of mounting other females. Naked-nape males—who probably constitute no more than 10 percent of the male population—rarely, if ever, mate with females. Thus, when naked-napes and nonmating residents and satellites are all taken into account, significant portions of the male Ruff population—perhaps more than half—are involved predominantly, if not exclusively, in sexual activity with other males. This homosexuality may be long-term—satellites, for example, almost never become residents during their entire lives (since these two classes differ genetically). Most male Buff-breasted Sandpipers that mount other males are probably functionally bisexual (if not predominantly heterosexual), since they also court and mate with females.

Birds who do not mate or breed are a notable feature of both Ruff and Buff-breasted Sandpiper populations (as noted above). More than 60 percent of male Ruffs, on average, do not copulate with females (this includes males of all categories), while more than half of all territorial Buff-breasted males do not mate (and many males in this species are not territorial and hence probably do not reproduce either). In many cases, males are unable to breed because females select which males they want to mate with and often refuse to allow certain males to copulate with them. However, females of both species occasionally choose more than one male to mate with: almost a quarter of all Buff-breasted nests contain eggs fathered by more than one male, while Reeves have been known to copulate with several different males in a row. Sometimes, more than one male will even try to copulate simultaneously with the same female—usually a resident and a satellite together. Cross-species sexual activity has also been observed: male Ruffs occasionally court and try to mount other sandpipers such as red knots (Calidris canutus).

Courtship and mating are virtually the only times during the entire breeding season when the two sexes are together: in both species, there is significant separation (both physical and temporal) between males and females. After copulating, female Ruffs often leave the lek and migrate farther north to lay their eggs—sometimes more than 1,800 miles away, and two to three weeks after they last mated. It is thought that females are able to do this because they store sperm in special glands in their reproductive tracts, effectively separating fertilization from insemination. Male Buff-breasts take no part in parenting, and in fact depart from the leks well before the eggs hatch. Male Ruffs also generally leave parenting entirely to the females, who occasionally cooperate amongst themselves in tending and defending their young. In fact, chicks may be killed by males if the two sexes ever interact following the hatching of eggs. Infanticide has not been observed in Buff-breasts, although about 10 percent of nests are abandoned by females if a predator takes some of the eggs. Sex segregation also occurs in Ruffs after the breeding season because males and females have different migratory patterns. Females tend to travel farther south to spend the winter, and at some wintering sites in Africa they may outnumber males 15 to 1.

*asterisked references discuss homosexuality/transgender

Cant, R. G. H. (1961) “Ruff Displaying to Knot.” British Birds 54:205.

*Cramp, S., and K. E. L. Simmons (eds.) (1983) “Ruff (Philomachus pugnax).” In Handbook of the Birds of Europe, the Middle East, and North Africa, vol. 3, pp. 385—402. Oxford: Oxford University Press.

*Hogan-Warburg, A.J. (1993) “Female Choice and the Evolution of Mating Strategies in the Ruff Philomachus pugnax (L.).” Ardea 80:395—403.

*———(1966) “Social Behavior of the Ruff, Philomachus pugnax (L.).” Ardea 54:109—229.

Hugie, D. M., and D. B. Lank (1997) “The Resident’s Dilemma: A Female Choice Model for the Evolution of Alternative Mating Strategies in Lekking Male Ruffs (Philomachus pugnax).” Behavioral Ecology 8:218—25.

*Lanctot, R. B. (1995) “A Closer Look: Buff-breasted Sandpiper.” Birding 27:384-90.

*Lanctot, R. B., and C. D. Laredo (1994) “Buff-breasted Sandpiper (Tryngites subruficollis).” In A. Poole and F. Gill, eds., The Birds of North America: Life Histories for the 21 st Century, no. 91. Philadelphia: Academy of Natural Sciences; Washington, D.C.: American Ornithologists’ Union.

Lank, D. B., C. M. Smith, O. Hanotte, T. Burke, and F. Cooke (1995) “Genetic Polymorphism for Alternative Mating Behavior in Lekking Male Ruff Philomachus pugnax.” Nature 378:59—62.

*Myers, J. P. (1989) “Making Sense of Sexual Nonsense.” Audubon 91:40—45.

———(1980) “Territoriality and Flocking by Buff-breasted Sandpipers: Variations in Non-breeding Dispersion.” Condor 82:241—50.

———(1979) “Leks, Sex, and Buff-breasted Sandpipers.” American Birds 33:823—25.

Oring, L. W. (1964) “Displays of the Buff-breasted Sandpiper at Norman, Oklahoma.” Auk 81:83—86.

Pitelka, F. A., R. T. Holmes, and S. F. MacLean, Jr. (1974) “Ecology and Evolution of Social Organization in Arctic Sandpipers.” American Zoologist 14:185—204.

Prevett, J. P., and J. F. Barr (1976) “Lek Behavior of the Buff-breasted Sandpiper.” Wilson Bulletin 88:500—503.

Pruett-Jones, S. G. (1988) “Lekking versus Solitary Display: Temporal Variations in Dispersion in the Buff-breasted Sandpiper.” Animal Behavior 36:1740—52.

*Scheufler, H., and A. Stiefel (1985) Der Kampfläufer [The Ruff]. Neue Brehm-Bücherei, 574. Wittenberg Lutherstadt: A. Ziemsen Verlag.

*Selous, E. (1906—7) “Observations Tending to Throw Light on the Question of Sexual Selection in Birds, Including a Day-to-Day Diary on the Breeding Habits of the Ruff (Machetes pugnax).” Zoologist 10:201—19, 285—94, 419—28; 11:60—6, 161—82, 367—80.

*Stonor, C. R. (1937) “On a Case of a Male Ruff (Philomachus pugnax) in the Plumage of an Adult Female.” Proceedings of the Zoological Society of London, Series A 107:85—88.

*van Rhijn, J. G. (1991) The Ruff: Individuality in a Gregarious Wading Bird. London: T. and A. D. Poyser.

———(1983) “On the Maintenance and Origin of Alternative Strategies in the Ruff Philomachus pugnax.” Ibis 125:482—98.

———(1973) “Behavioral Dimorphism in Male Ruffs, Philomachus pugnax (L.).” Behavior 47:153—229.

Outside of the mating season, Greenshanks congregate in flocks of 20–25 birds, while Redshanks are less social and may even be solitary. During the mating season, monogamous pairs are the predominant social unit, although a number of variations occur, including nonbreeding birds (see below).

Behavioral Expression: In both Greenshanks and Redshanks, males sometimes court and copulate with each other. Homosexual courtship in Greenshanks involves spectacular aerial and ground displays, employing patterns also found in heterosexual courtship. One male may pursue another in a NUPTIAL FLIGHT, which starts out as a twisting, careening chase low over the ground, followed by a remarkable ascent of both birds to a great altitude. The two males swerve and turn in unison as they climb higher, sometimes disappearing completely into the clouds; the “sky dance” comes to a dramatic close as the males plummet back to earth in a steep dive. In the ground courtship display, two males bow, fan their tails, flap their wings, and utter deep growling calls or chip, quip, and too-hoo notes. This may lead to copulation (often performed on a stump or tree branch), in which one male flutters onto the back of another, lowering his body to make contact with the other while slowly flapping his wings. Homosexual copulation may be briefer than the corresponding heterosexual behavior. Males also sometimes try to copulate with other males that are calling in the treetops, and with males whose female mates are incubating eggs (in the latter cases, the female often makes a threatening or challenging call during the homosexual interaction). Male Greenshanks are also sometimes courted by male Green Sandpipers (Tringa ochropus), who approach them from behind with drooping wings and raised, partially fanned tails. The Sandpipers may also try to mount them; in contrast to within-species homosexual matings, male Greenshanks typically resist these sexual advances, shaking the Sandpipers off and violently pecking at them.

Male Redshanks court other males with a GROUND CHASE (also used in heterosexual courtship). In this display, one male pursues another in a series of curves and circles, often running in a distinctive sideways motion—similar to that of a crab—with ruffled feathers and fanned tail. The pursuing male may give a “mate-call” consisting of repeated paired notes: tyoo-tyoo… tyoo-tyoo…, and both birds also sometimes make chipping or trilled calls during the chase. Occasionally one male also mounts the other and tries to copulate with him, although his advances are often rebuked by the other male (as also frequently happens in heterosexual copulations).

Frequency: Homosexual courtship and copulation probably occur only occasionally in Greenshanks and Redshanks, although no systematic long-term studies of their prevalence have yet been undertaken.

Orientation: In many cases, individuals that engage in same-sex activity are bisexual. Male Greenshanks and Redshanks court birds of both sexes, while male Greenshanks are sometimes heterosexually paired fathers when they participate in homosexual copulations with other males. In at least one case, a male Greenshank associated himself with a heterosexual pair and tried to copulate with both the male and the female (although it is not known whether that male himself was single or paired with a female).

Sexual behavior in these two Sandpipers often occurs at times when fertilization is not possible: male Greenshanks and Redshanks court and mate with females after eggs are laid, both during incubation and following the hatching of chicks. In addition, REVERSE mounting (in which the female mounts the male) also occurs in Greenshanks. Courtship and copulation with other species of sandpipers have been recorded, including lesser yellowlegs (Tringa flavipes) and Green Sandpipers (as noted above). A wide variety of alternative heterosexual mating and parenting arrangements are also found in these birds. Although both Greenshanks and Redshanks are primarily monogamous, males of both species sometimes court and mate with females other than their own mate. In addition, some individuals engage in a number of different polygamous mating arrangements: occasional trios occur in both species, composed of two females and a male. Both females may lay in the same nest, they may have separate nests, or one female may be nonbreeding. Redshanks sometimes also participate in serial polygamy, in which a male mates with a second female, or a female with a second male, after laying a clutch with a first mate. This involves deserting or “divorcing” the first mate, who then typically raises the young as a single parent. (In Greenshanks, another form of “single parenting” occasionally occurs, in which the male partner fails to help the female incubate the eggs, but remains paired with her.) In fact, about 11 percent of Redshanks (and up to a quarter of Greenshanks) change partners between or within breeding seasons (this is more common among males), and only about a third of all males and half of all females mate for life. Some birds may divorce and re-pair with up to four different partners during their lives. In a few cases, female Redshanks have even left their mate to pair with another male, only to return to their “ex” the following season and remain with him for many more years. Adoption or foster-parenting also takes place in Redshanks: females sometimes lay eggs in other females’ nests (who then raise all the chicks as their own), and Redshanks have even been seen taking care of chicks of other species of shorebirds, such as the avocet (Recurvirostra avosetta).

Some Greenshanks do not participate in breeding at all—about a quarter of all males, on average, do not procreate (and in some years this figure may be higher—nearly half of all males). This includes both single birds and those that are heterosexually paired but do not breed. Such nonbreeding pairs constitute an average of more than 15 percent of pairs, though in some years more than a third do not reproduce. Heterosexual relations may also be marked by unwillingness and aggression between the sexes: female Redshanks sometimes turn on males that are chasing them during courtship, staving off their advances with prolonged fights involving much pecking and scratching. Females of both species may also refuse to allow males to mount them: about a third of all Redshank heterosexual mating attempts, for example, are not completed due to female refusal.

*asterisked references discuss homosexuality/transgender

*Cramp, S., and K. E. L. Simmons (eds.) (1983) “Redshank (Tringa totanus).” In Handbook of the Birds of Europe, the Middle East, and North Africa, vol. 3, pp. 531—35. Oxford: Oxford University Press.

Garner, M. S. (1987) “Lesser Yellowlegs Attempting to Mate with Redshank.” British Birds 80:283.

Hakansson, G. (1978) “Incubating Redshank, Tringa totanus, Warming Young of Avocet, Avocetta recurvirostra.” Vår Fågelvårld 37:137—38.

*Hale, W. G. (1980) Waders. London: Collins.

*Hale, W. G., and R. P. Ashcroft (1983) “Studies of the Courtship Behavior of the Redshank Tringa totanus.” Ibis 125:3—23.

*———(1982) “Pair Formation and Pair Maintenance in the Redshank Tringa totanus.” Ibis 124:471—501.

*Nethersole-Thompson, D. (1975) Pine Crossbills: A Scottish Contribution. Berkhamsted: T. and A. D. Poyser.

*———(1951) The Greenshank. London: Collins.

*Nethersole-Thompson, D., and M. Nethersole-Thompson (1986) Waders: Their Breeding, Haunts, and Watchers. Calton: T. and A. D. Poyser.

*———(1979) Greenshanks. Vermillion, S.D.: Buteo Books.

Thompson, D. B. A., P. S. Thompson, and D. Nethersole-Thompson (1988) “Fidelity and Philopatry in Breeding Redshanks (Tringa totanus) and Greenshanks (T. nebularia).” In H. Ouellet, ed., Acta XIX Congressus Internationalis Ornithologici (Proceedings of the 19th International Ornithological Congress), 1986, Ottawa, vol. I, pp. 563—74. Ottawa: University of Ottawa Press.

———(1986) “Timing of Breeding and Breeding Performance in a Population of Greenshanks (Tringa nebularia).” Journal of Animal Ecology 55:181—99.

The primary social unit among Stilts is the monogamous mated pair; Black-winged couples often nest in loose colonies containing 2—50 families, while Black Stilts are less gregarious. Outside of the mating season, the birds gather in flocks of usually up to ten individuals, although assemblies of hundreds of Black-winged Stilts may also occur.

Behavioral Expression: Lesbian pairs occur in both Black-winged and Black Stilts. In these partnerships, two females participate in courtship, copulation, and parenting activities together. Homosexual pairing and courtship in Black-winged Stilts often begins with a ritual NEST DISPLAY activity: each female takes turns symbolically “showing” the other a nest location by squatting on land as if she were incubating eggs, and making pecking motions in the mud as though she were turning the eggs over. Although heterosexual pairings also frequently commence with this activity, in lesbian pairs the two birds may spend considerably more time engaged in nest display. This may lead to full-scale courtship activities, such as DIBBLING—bill dipping and shaking by both partners, involving prominent splashing of water—and ritual preening, in which one female preens the side of her breast nearest to the other female, frequently combined with more splashing activity. Often one female takes up the NECK EXTENDED posture, a stylized pose in which she stands with her legs slightly apart and her neck lowered and extended just above the surface of the water. While one female is standing in this position, the other performs a courtship dance in which she moves back and forth behind her partner, striding in semicircles from one side to the other. The two females may participate in continuous courtship activities for up to three-quarters of an hour at a time. Sexual activity also takes place between members of a lesbian pair, with one female mounting the other as in heterosexual copulation.

Once bonded, the pair vigorously defends their territory against any intruding families and eventually builds a nest together. Because both females sometimes lay eggs, the nests of lesbian pairs often contain SUPERNORMAL CLUTCHES of 7–8 eggs, up to twice as many as those of heterosexual pairs (which usually have only 3–4 eggs). Both females take turns incubating the eggs; in heterosexual pairs the two birds also share incubation duties, but in many cases the female contributes a disproportionately greater amount of time than does the male. If the eggs are eaten by predators, the lesbian pair replaces them by laying a second clutch (as often happens with heterosexual parents as well). Most eggs laid by same-sex pairs are probably infertile. Like heterosexual pairs, some Black-winged Stilt lesbian pairs divorce. This may occur, for example, when one female forms a new pair-bond with another female. Although mate-switching may initially be accompanied by aggression between the separating females, the divorced partner sometimes still remains “friends” with the new pair, being allowed to visit their territory (unlike other birds, which are routinely chased away).

Frequency: In Black-winged Stilts, female pairs may constitute anywhere from 5–17 percent of the total number of pairs (depending on the population), while about 2 percent of Black Stilt pairings are lesbian. Homosexual copulation occurs at fairly high rates in some Black-winged Stilt female pairs: in one case, two females were seen to mate with each other as often as five times in one day.

Orientation: Because the eggs they lay are usually infertile, it is likely that many female Black-winged Stilts in lesbian pairs are exclusively homosexual, i.e., they do not copulate with males (at least for the duration of their bond). In addition, some females show a persistent orientation toward other females, since they remate with another female if their lesbian partnership breaks up.

In addition to long-lasting monogamous pairs, a variety of alternative heterosexual family arrangements occur in Stilts. Black Stilts occasionally form trios of two females and one male (with both females laying eggs), while Black-winged Stilt pairs sometimes adopt chicks from other families and foster-parent them along with their own. Divorce and remating may occur in male-female pairs of Black-winged Stilts, and some males engage in courtship and copulation with females other than their mates. In Black Stilts, heterosexual pairs sometimes separate when their young fledge: the male often takes the juveniles with him as a single parent when he migrates, while the female remains behind. On returning, the male may get back together with his previous partner, or the female may find a new mate. In some intact Black Stilt families, fathers maybe abusive toward their young, behaving aggressively or rejecting their male offspring (although this has so far only been reported in captivity). In both of these Stilt species, individuals often masturbate by mounting an inanimate object (such as a piece of driftwood) and performing copulatory movements. In Black-winged Stilts this behavior may occur with extraordinary frequency—one bird was recorded making 20–30 such masturbatory mounts in one session, roughly once every 30 seconds. Finally, birds sometimes pair with individuals outside of their species: in some populations, about 30 percent of Black Stilts mate with Black-winged Stilts, and hybrids of the two species are common.

*asterisked references discuss homosexuality/transgender

Cramp, S., and K. E. L. Simmons, eds. (1983) “Black-winged Stilt (Himantopus himantopus).” In Handbook of the Birds of Europe, the Middle East, and North Africa, vol. 3, pp. 36-47. Oxford: Oxford University Press.

Goriup, P. D. (1982) “Behavior of Black-winged Stilts.” British Birds 75:12–24.

Hamilton, R. B. (1975) Comparative Behavior of the American Avocet and the Black-necked Stilt (Recurvirostridae). Ornithological Monographs no. 17. Washington, DC: American Ornithologists’ Union.

Kitagawa, T. (1989) “Ethosociological Studies of the Black-winged Stilt Himantopus himantopus himantopus. I. Ethogram of the Agonistic Behaviors.” Journal of the Yamashina Institute of Ornithology 21:52–75.

*———(1988a) “Ethosociological Studies of the Black-winged Stilt Himantopus himantopus himantopus. III. Female-Female Pairing.” Japanese Journal of Ornithology 37:63–67.

———(1988b) “Ethosociological Studies of the Black-winged Stilt Himantopus himantopus himantopus. II. Social Structure in an Overwintering Population.” Japanese Journal of Ornithology 37:45—62.

*Pierce, R. J. (1996a) “Recurvirostridae (Stilts and Avocets).” In J. del Hoyo, A. Elliott, and J. Sargatal, eds., Handbook of the Birds of the World, vol. 3: Hoatzin to Auks, pp. 332—47. Barcelona: Lynx Edicións.

———(1996b) “Ecology and Management of the Black Stilt Himantopus novaezelandiae.” Bird Conservation International 6:81–88.

(1986) Black Stilt. Endangered New Zealand Wildlife Series. Dunedin, New Zealand: John McIndoe and New Zealand Wildlife Service.

*Reed, C. E. M. (1993) “Black Stilt.” In S. Marchant and P. J. Higgins, eds., Handbook of Australian, New Zealand, and Antarctic Birds, vol. 2, pp. 769—80. Melbourne: Oxford University Press.

Oystercatchers and Golden Plovers commonly associate in flocks. The mating system typically involves monogamous pair-bonding, although many alternative arrangements also occur (see below). Nonbreeding Oystercatchers tend to aggregate in groups known as CLUBS.

Behavioral Expression: Oystercatchers sometimes participate in same-sex courtship and copulation. This behavior typically occurs within bisexual trios, that is, an association of three birds—two of one sex and one of the other—in which all three members have a bonded sexual relationship. For example, two males and a female sometimes form a trio, and in addition to heterosexual activity between the opposite-sex partners, the two males may court and mount each other. Several different courtship and pair-bonding displays are used in both same-sex and opposite-sex contexts. For example, while walking around each other, two males might perform BALANCING, in which they make seesaw movements with their bodies, or the THICK-SET ATTITUDE, a stylized posture in which the head is drawn down between the shoulders with the tail and back horizontal, all the while bending the legs and making tripping steps. Sometimes two males also perform ritualized nest-building activities as part of their mutual courtship, such as THROWING STRAWS, in which they toss straw and other materials backward, or PRESSING A HOLE, in which they repeatedly sit down, pressing their breasts and wings against the ground as if fashioning a nest. As a prelude to copulation, one male approaches the other in the STEALTHY ATTITUDE, similar to the thick-set attitude except that the head is held to one side and the tail is pressed down and spread. One male may mount and try to copulate with the other, although sometimes his sexual advances are thwarted by an attack from the other male. Interestingly, all three members of such a trio may be nonmonogamous, engaging in heterosexual courtship or copulations with birds other than their primary partners.

Homosexual activities also occur between two female Oystercatchers that form part of a bisexual trio with a male. Most associations of this type start off the way heterosexual trios do, with considerable aggression between the females, but eventually they develop a strong bond with each other. They preen one another while remaining close together and also cooperate (along with their male partner) in mutual defense of their territory. Employing the same behavior patterns seen in heterosexual mating, the two females also regularly copulate with one another: one female approaches the other in a hunched posture, making soft pip-pip noises while her partner tosses her tail upward. Then, while mounting, the female flaps her wings to maintain balance and may push her tail under the other female’s in order to achieve genital (cloacal) contact, at which point she utters soft wee-wee sounds. The two birds may take turns mounting one another, and about 47 percent of lesbian copulations include full genital contact (compared to 67 percent of matings by heterosexual pairs and 74 percent of male-female copulations in heterosexual trios). The females also mate regularly with their male partner, eventually building a joint nest together in which they each lay eggs. This results in a SUPERNORMAL CLUTCH of up to 7 eggs (compared to a maximum of 4–5 in nests of heterosexual pairs, or in each of the two separate nests of heterosexual trios). All three partners take turns incubating the eggs and they cooperate in raising their chicks. However, because each bird is usually unable to adequately cover all 7 eggs simultaneously, bisexual trios generally hatch and raise fewer offspring than do heterosexual pairs. Bisexual trios can remain together for up to 4–12 years, comparable to Oystercatcher heterosexual pairs, and are actually more stable and longer-lasting than heterosexual trios (which typically do not extend beyond 4 years).

Male Golden Plovers occasionally court and pair with each other in the early spring. Courtship activities often begin with ground displays, in which one male chases the other with his head lowered, wings half-spread, and back feathers ruffled, all the while raising and lowering his fanned tail. This may develop into a spectacular twisting aerial pursuit flight, in which the two males synchronously dip and climb, careening and skimming over the ground in a dramatic, high-speed chase that may take them far from their home territories.

Frequency: Homosexual behavior occurs occasionally in Oystercatcher and Golden Plover populations. Less than 2 percent of Oystercatchers, for example, live in trios of two females with one male, although 43 percent of such associations involve homosexual bonding and sexual activities. Overall, about 1 in every 185 copulations is between two females; lesbian matings take place roughly once every 6–7 hours within each bisexual trio, compared to roughly once every 3–6 hours for heterosexual matings (in a pair or trio). Likewise, approximately 1 out of every 400 Oystercatcher bonds involves a trio of two males with a female, and only some of these include same-sex activity. As in bisexual trios with two females, however, homosexual behavior may be fairly frequent within the association: in one such trio, for instance, almost two-thirds of all courtship activities were homosexual, and 15— 19 percent of all mounting activities were same-sex.

Orientation: Oystercatchers that participate in same-sex activities are usually bisexual, being part of a bonded trio with a member of the opposite sex and sometimes also engaging in promiscuous heterosexual activities. Within the trio, however, one bird may be more homosexually oriented than the other, i.e., it may have a closer bond with a bird of the same sex, while the other may have a stronger heterosexual bond. In one bisexual trio involving two males and a female, for example, 85 percent of one male’s courtship activities and more than a third of his mounting activities were homosexual; for the other male, about 70 percent of his courtships and a quarter of his mounting activities were same-sex. Some female Oystercatchers in bisexual trios also end up leaving their trio and pairing with a male, although this occurs less frequently than for females in heterosexual trios.

Polygamous heterosexual trios (without same-sex activities) sometimes form in Oystercatchers (as mentioned above), and the same phenomenon also occurs in Golden Plovers. In addition, several other variations on the long-term, monogamous, male-female parenting unit have developed in these species. Although pair-bonds in Oystercatchers and Golden Plovers sometimes last for life, heterosexual partners may divorce and re-pair with new mates. In some Oystercatcher populations 6—10 percent of couples divorce, and the average length of a pair-bond is only two to three years. Some birds (particularly females) divorce repeatedly and may have as many as six or seven different partners during their lives, and only about half of all birds remain with the same partner for life. A female Golden Plover sometimes deserts her mate during the breeding season (often to start a second family with a new male); her former mate must then raise their young on his own. In addition to single parenting, “double-family parenting” sometimes occurs: two Plover families occasionally share the same territory (with one couple breeding earlier than the other) and may help defend each other’s brood. Oystercatcher pairs sometimes foster-parent chicks of other related species such as lapwings (Vanellus vanellus) and avocets (Recurvirostra avosetta), occasionally even “adopting” and hatching foreign eggs.

Infidelity is a prominent feature of Oystercatcher pair-bonds. Up to 7 percent of all copulations are nonmonogamous, often between a paired female and a single male (and usually initiated by the female). Females often have an extended “affair” with a particular male over several years and may eventually leave their mate to pair with him; some females are even unfaithful to their new partner by continuing to copulate with their “ex” after they have remated. However, nonmonogamous mates are not generally more likely to divorce than strictly monogamous pairs, and in fact some evidence suggests that Oystercatchers who engage in outside sexual activity are actually more likely to stay together. One study found that 0–5 percent of unfaithful birds divorced, while 11 percent of monogamous ones did. Many nonmonogamous matings are nonreproductive, occurring too early in the breeding season for fertilization to be possible, or between nonbreeders; in fact, only 2–5 percent of all chicks are the result of infidelities. There are several distinct categories of nonbreeders in this species, including nonbreeding pairs with territories (about 5 percent of all pairs) and FLOATERS without any territories. Overall, about 30 percent of the adult population is nonbreeding. Nevertheless, such birds still engage in sexual behavior, both with each other and with paired birds. Nonbreeding pairs and individuals also occur in Golden Plovers, and on average about half of the population is nonreproductive at any time.

Many within-pair copulations are also nonprocreative, with about 40 percent occurring too early or too late in the breeding season (for Oystercatchers), or during incubation. In addition, it has been estimated that each Oystercatcher pair copulates about 700 times during the breeding season—far in excess of the amount required for reproduction. Oystercatchers also sometimes practice nonreproductive REVERSE copulations, in which the female mounts the male. And as mentioned above, a quarter to a third of mounts between heterosexual mates do not involve genital contact; many such copulations are incomplete because the female throws the male off her back or otherwise refuses to participate. Much more rarely, a male will rape or forcibly copulate with a nonconsenting female. Adult-youngster interactions are also sometimes marked by violence and neglect: Oystercatcher chicks have been viciously attacked and even killed when they stray into another bird’s territory. In addition, LEAPFROG parents often starve their chicks by failing to bring them enough food. Leapfrog birds are those whose nesting territories are located farther inland, separate from the feeding territories, hence to obtain food they must “leapfrog” over birds that nest directly adjacent to the shore. Studies have shown that the territories of such Oystercatchers do not, however, place undue time or energy constraints on them compared to nonleapfrogs. Thus, the fact that their chicks sometimes starve is due more to inadequate parental care than to their suboptimal territories.

*asterisked references discuss homosexuality/transgender

Edwards, P. J. (1982) “Plumage Variation, Territoriality, and Breeding Displays of the Golden Plover Pluvialis apricaria in Southwest Scotland.” Ibis 124:88—96.

*Ens, B. J. (1998) “Love Thine Enemy?” Nature 391:635—37.

*———(1996) Personal communication.

———(1992) “The Social Prisoner: Causes of Natural Variation in Reproductive Success of the Oystercatcher.” Ph.D. thesis., University of Groningen.

Ens, B. J., M. Kersten, A. Brenninkmeijer, and J. B. Hulscher (1992) “Territory Quality, Parental Effort, and Reproductive Success of Oystercatchers (Haematopus ostralegus).” Journal of Animal Ecology 61:703—15.

Ens, B. J., U. N. Safriel, and M. P. Harris (1993) “Divorce in the Long-lived and Monogamous Oystercatcher, Haematopus ostralegus: Incompatibility or Choosing the Better Option?” Animal Behavior 45:1199—217.

Hampshire, J. S., and F. J. Russell (1993) “Oystercatchers Rearing Northern Lapwing Chick.” British Birds 86:17-19.

Harris, M. P., U. N. Safriel, M. de L. Brooke, and C. K. Britton (1987) “The Pair Bond and Divorce Among Oystercatchers Haematopus ostralegus on Skokholm Island, Wales.” Ibis 129:45—57.

*Heg, D. (1998) Personal communication.

Heg, D., B. J. Ens, T. Burke, L. Jenkins, and J. P. Kruijt (1993) “Why Does the Typically Monogamous Oystercatcher (Haematopus ostralegus) Engage in Extra-Pair Copulations?” Behavior 126:247—89.

*Heg, D., and R. van Treuren (1998) “Female-Female Cooperation in Polygynous Oystercatchers.” Nature 391:687-91.

*Makkink, G. F. (1942) “Contribution to the Knowledge of the Behavior of the Oyster-Catcher (Haematopus ostralegus L.).” Ardea 31:23-74.

*Nethersole-Thompson, D., and C. Nethersole-Thompson (1961) “The Breeding Behavior of the British Golden Plover.” In D. A. Bannerman, ed., The Birds of the British Isles, vol.10, pp. 206-14. Edinburgh and London: Oliver and Boyd.

*Nethersole-Thompson, D., and M. Nethersole-Thompson (1986) Waders: Their Breeding, Haunts, and Watchers. Calton: T. and A. D. Poyser.

Parr, R. (1992) “Sequential Polyandry by Golden Plovers.” British Birds 85:309.

———(1980) “Population Study of Golden Plover Pluvialis apricaria, Using Marked Birds.” Ornis Scandinavica 11:179-89.

———(1979) “Sequential Breeding by Golden Plovers.” British Birds 72:499-503.

Tomlinson, D. (1993) “Oystercatcher Chick Probably Killed by Rival Adult.” British Birds 86:223—25.

GULLS AND TERNS

Common Gulls are fairly sociable, often associating in flocks of up to 100 individuals; sometimes tens of thousands of birds congregate outside of the breeding season. Ring-billed Gulls are also gregarious. Birds of both species generally form monogamous pair-bonds (although several variations exist—see below). Nesting colonies in Common Gulls contain a few dozen to several hundred pairs, while Ring-billed colonies can be much larger, in the tens of thousands of pairs.

Behavioral Expression: Both Ring-billed and Common Gull females sometimes develop homosexual bonds, build nests together, lay and incubate eggs, and successfully raise chicks. Same-sex pairs are often long-lasting (as are heterosexual pair-bonds in these species), and females generally return to the same nest site with their female partner each year. Of five homosexual pairs of Ring-billed Gulls tracked over time, for example, all remained together over more than one mating season, while homosexual bonds lasting for at least eight years have been documented in female Common Gulls. Some pairs do divorce between mating seasons, however, as do some heterosexual pairs. In addition, female Ring-billed Gulls on rare occasions switch mates during a mating season, first pairing with one female, then with another. Same-sex bonds in this species also show a number of other interesting features that are rarely found in female homosexual bonds in other animals. For example, one or both partners in a homosexual pair are often younger females: couples in which there is an age difference between the two females—one an adult, the other an adolescent or younger adult—are particularly common in some populations. In addition, some female Ring-billed Gulls form homosexual trios consisting of three birds that are all simultaneously bonded to one another. In Common Gulls, homosexual pairs may after several years develop into bisexual trios. This occurs when a male joins them and is accepted into their association, bonding with one or both females (who nevertheless still retain their bond with each other). In Ring-billed Gulls, the opposite scenario may occur: in at least one case, two females in a bisexual trio remained paired to each other after the male left their association. Ring-billed Gulls in homosexual pairs probably do not engage in a great deal of courtship activity (unlike heterosexual or homosexual pairs in other species).

The first breeding season that female Common Gulls begin a pair-bond, they may build a “double nest” consisting of two separate but touching nest cups; in subsequent years, they will build only a single nest in which they both lay eggs (like most Ring-billed female pairs). Since both partners usually lay eggs, nests of homosexual pairs often contain “oversize” or SUPERNORMAL CLUTCHES of 5–8 eggs (Ring-billed Gull) and 6 eggs (Common Gull)—up to twice the number found in heterosexual nests. Some Ring-billed Gulls in female couples may also lay their eggs in the nests of other (heterosexual) pairs. One or both partners in pairs of female Ring-billed Gulls may mate nonmonogamously with a male so that some of their eggs will be fertilized. Female Common Gulls in bisexual trios can also lay fertile eggs by mating with their male partner. Both females share incubation duties and also cooperate in parenting the chicks that they hatch. Homosexual parents in Ring-billed Gulls invest as much time as their heterosexual counterparts do in feeding their chicks, spending time on the nesting territory, and defending their territory. They may actually work harder than male-female pairs in brooding and defending their chicks, with the result that offspring of female pairs often have a faster growth rate than chicks of heterosexual parents.

Nevertheless, chicks belonging to female pairs are often less robust on hatching, and female parents generally raise less than half the number of chicks that male-female pairs do. However, these traits are also characteristic of supernormal clutches belonging to heterosexual trios and are therefore undoubtedly related to the larger clutch size rather than the sex or abilities of the parents. In addition, in some populations female pairs are relegated to smaller, substandard territories on the periphery of the breeding colony or in between other territories (as are less experienced heterosexual pairs). In some cases, homosexual pairs actually appear to form clusters of up to ten nests in close proximity, or else small groups of two or three (sometimes in a straight-line or triangular formation). Many of these nests are located in areas where it is more difficult to parent successfully—places with little or no vegetation, or else away from the beach—and therefore it is remarkable that female pairs are able to successfully raise chicks as often as they do in such less than optimal conditions.

Frequency: There is wide variation in the incidence of female pairing in Ring-billed Gulls. In some populations—especially in growing colonies—as many as 6–12 percent of the pairs are homosexual. In other colonies, they are less common—1–3 percent of all pairs—and in some locations as few as 1 in 700 or 1 in 3,400 nests may belong to a female pair. Overall, pair-bonds between females probably occur only occasionally in Common Gulls, although at one study site, 1 pair out of a total of 12 was homosexual.

Orientation: There is an equally wide variation in the proportion of heterosexual, bisexual, and homosexual orientations among Ring-billed Gulls. In some populations, less than a third of all eggs laid by female pairs are fertile, indicating that the majority of such females are exclusively homosexual (at least for the duration of their pair-bond). In other colonies, egg fertility of female pairs is much higher—two-thirds to nearly 90 percent—indicating a greater prevalence of bisexual activity. Even among such females, however, there is further variation. In some same-sex couples, both females mate with males and lay fertile eggs; in others, only one partner does, or each partner might lay both fertile and infertile eggs at different times, indicating temporal variation in bisexual activity. Similarly, in a Common Gull bisexual trio, one female remained exclusively homosexual even though her female partner mated with the male. In addition, a large number of “heterosexual” Ring-billed females may have a “latent” bisexual potential, since many are able to develop bonds with other females if single males are not available.

Heterosexual pairs in Ring-billed and Common Gulls exhibit a variety of bonding and parenting arrangements (like homosexual pairs). Not all males and females couple for life: the heterosexual divorce rate is about 28 percent in both species. Polygamous heterosexual trios—two females bonded to the same male, but not to each other—are also found in both species, as are occasionally even quartets (three females with one male). Common Gull pairs sometimes foster-parent chicks, while another form of “adoption” occurs in these species when females occasionally lay eggs in nests belonging to other pairs or roll eggs from other nests into their own. Moreover, because of parental ineptitude or inefficiency (such as poor feeding), at least 8 percent of Ring-billed chicks abandon or “run away” from their own families; most of these are adopted and cared for by other families.

About 4 percent of Ring-billed pairs continue to engage in courtship and copulation after the hatching of their eggs—when sexual activity is not directly reproductive—and about 5 percent of adults court and mount chicks. Most of this activity involves females behaving incestuously with their own offspring, including full copulatory REVERSE mounts of young birds. Mounted chicks may be as young as two weeks old, and they usually collapse under the weight of the adult mounting them and cry out in distress. Some individuals appear to be “habitual molesters” in that they repeatedly interact sexually with chicks, including their own. In addition to sexual molestation, Ring-billed chicks are often subjected to vicious attacks from neighboring adults when their parents are away, or if they stray outside of their home territory. About 1 in 300 chicks is killed by such assaults, and infanticide can account for between 5 percent and 80 percent of all chick deaths (depending on the population).

Female pairs that lay supernormal clutches also occur in California Gulls (Larus californicus), where they constitute about 1 percent of all pairs.

*asterisked references discuss homosexuality/transgender

Brown, K. M., M. Woulfe, and R. D. Morris (1995) “Patterns of Adoption in Ring-billed Gulls: Who Is Really Winning the Inter-generational Conflict?” Animal Behavior 49:321—31.

*Conover, M. R. (1989) “Parental Care by Male-Female and Female-Female Pairs of Ring-billed Gulls.” Colonial Waterbirds 12:148—51.

*———(1984a) “Frequency, Spatial Distribution, and Nest Attendants of Supernormal Clutches in Ring-billed and California Gulls.” Condor 86:467-71.

*———(1984b) “Consequences of Mate Loss to Incubating Ring-billed and California Gulls.” Wilson Bulletin 96:714—16.

*———(1984c) “Occurrence of Supernormal Clutches in the Laridae.” Wilson Bulletin 96:249-67.

*Conover, M. R., and D. E. Aylor (1985) “A Mathematical Model to Estimate the Frequency of Female-Female or Other Multi-Female Associations in a Population.” Journal of Field Ornithology 56:125-30.

*Conover, M. R., and G. L. Hunt, Jr. (1984a) “Female-Female Pairings and Sex Ratios in Gulls: A Historical Perspective.” Wilson Bulletin 96:619—25.

*———(1984b) “Experimental Evidence That Female-Female Pairs in Gulls Result From a Shortage of Males.” Condor 86:472—76.

*Conover, M. R., D.E. Miller, and G. L. Hunt, Jr. (1979) “Female-Female Pairs and Other Unusual Reproductive Associations in Ring-billed and California Gulls.” Auk 96:6—9.

Emlen, J. R., Jr. (1956) “Juvenile Mortality in a Ring-billed Gull Colony.” Wilson Bulletin 68:232—38.

Fetterolf, P. M. (1983) “Infanticide and Non-Fatal Attacks on Chicks by Ring-billed Gulls.” Animal Behavior 31:1018—28.

———(1984) “Ring-billed Gulls Display Sexually Toward Offspring and Mates During Post-Hatching.” Wilson Bulletin 96:12—19.

*Fetterolf, P. M., and H. Blokpoel (1984) “An Assessment of Possible Intraspecific Brood Parasitism in Ring-billed Gulls.” Canadian Journal of Zoology 62:1680—84.

*Fetterolf, P. M., P. Mineau, H. Blokpoel, and G. Tessier (1984) “Incidence, Clustering, and Egg Fertility of Larger Than Normal Clutches in Great Lakes Ring-billed Gulls.” Journal of Field Ornithology 55:81—88.

*Fox, G. A., and D. Boersma (1983) “Characteristics of Supernormal Ring-billed Gull Clutches and Their Attending Adults.” Wilson Bulletin 95:552—59.

Kinkel, L. K., and W. E. Southern (1978) “Adult Female Ring-billed Gulls Sexually Molest Juveniles.” Bird-Banding 49:184—86.

*Kovacs, K. M., and J. P. Ryder (1985) “Morphology and Physiology of Female-Female Pair Members.” Auk 102:874—78.

*———(1983) “Reproductive Performance of Female-Female Pairs and Polygynous Trios of Ring-billed Gulls.” Auk 100:658—69.

*———(1981) “Nest-site Tenacity and Mate Fidelity in Female-Female Pairs of Ring-billed Gulls.” Auk 98:625—27.

*Lagrenade, M., and P. Mousseau (1983) “Female-Female Pairs and Polygynous Associations in a Quebec Ring-billed Gull Colony.” Auk 100:210—12.

Nethersole-Thompson, C., and D. Nethersole-Thompson (1942) “Bigamy in the Common Gull.” British Birds 36:98—100.

*Riddiford, N. (1995) “Two Common Gulls Sharing a Nest.” British Birds 88:112—13.

*Ryder, J. P. (1993) “Ring-billed Gull.” In A. Poole, P. Stettenheim, and F. Gill, eds., The Birds of North America: Life Histories for the 21st Century, no. 33. Philadelphia: Academy of Natural Sciences; Washington, D.C.: American Ornithologists Union.

*Ryder, J. P., and P. L. Somppi (1979) “Female-Female Pairing in Ring-billed Gulls.” Auk 96:1—5.

Southern, L. K., and W. E. Southern (1982) “Mate Fidelity in Ring-billed Gulls.” Journal of Field Ornithology 53:170—71.

Trubridge, M. (1980) “Common Gull Rolling Eggs from Adjacent Nest into Own.” British Birds 73:222—23.

Western Gulls and Kittiwakes form pair-bonds and nest in colonies, some of which contain upwards of 10,000 pairs; Kittiwakes often nest on cliffs. Outside of the breeding season they are less sociable, occasionally gathering in loose aggregations when not solitary.

Behavioral Expression: Female Western Gulls sometimes form homosexual pairs, as do Kittiwakes. In Western Gulls, the females participate in courtship, sexual, and parenting behaviors similar to those of heterosexual pairs in their basic patterns, yet different in many details. Two females court one another by performing HEAD-TOSSING (a stylized bobbing of the head with the bill pointed skyward) and COURTSHIP-FEEDING (in which a small amount of food is regurgitated and offered as a “gift” to the partner). In heterosexual pairs, males usually perform more courtship-feeding and females more head-tossing. In homosexual pairs, both birds perform these behaviors—often with equal frequency—although the overall rate of courtship behaviors for each female is similar to females in heterosexual pairs. Homosexual courtship-feeding differs from the heterosexual pattern in that a female does not offer as large an amount of food to her female partner and may even swallow the “offering” herself rather than give it to her mate. In some female pairs, one partner regularly mounts the other and may even utter the copulation call characteristic of heterosexual matings. Some females adopt unique mounting positions such as sideways or head-to-tail (not seen in heterosexual matings), and genital contact does not usually occur. Like heterosexual pairs, female couples establish territories that they defend against intruders. Both females spend a great deal of time on their territories (typical only of females in heterosexual pairs), while both also exhibit aggressive reactions to intruders (more typical of males in heterosexual pairs). Once a homosexual pair-bond is established, it usually persists for many years, and the two females return to the same territory each season: one study that tracked eight homosexual pairs found that seven of them remained together for more than one breeding season.

Homosexual pairs usually build a nest in which both females lay eggs; the resulting SUPERNORMAL CLUTCH contains 4–6 eggs in Western Gulls, up to twice the number found in nests of heterosexual pairs. Some of these eggs are fertile because females in homosexual pairs occasionally copulate with males (without breaking their same-sex bond). Although eggs laid by female pairs may be smaller than those of heterosexual females, homosexual parents successfully hatch and raise chicks, sharing all parental duties.

Frequency: As many as 10–15 percent of Western Gull pairs in some populations are homosexual; the percentage is much lower in Kittiwakes, about 2 percent of all pairs.

Orientation: Most female pairs in Kittiwakes are exclusively homosexual, never mating with males and laying only infertile eggs; the same is true for many pairs in Western Gulls. However, up to 15 percent of eggs laid by Western Gull same-sex pairs are fertilized, so at least some females are simultaneously bisexual—copulating with males while retaining their homosexual pair-bond.

Not all heterosexual birds in these species form lifelong, monogamous pair-bonds within which they raise their own young. About 30 percent of Kittiwake male-female pairs divorce. Some birds form polygamous trios consisting of one male bonded with two females, each with her own nest (about 3 percent of all bonds). Western Gull pairs (and rarely, single males) sometimes adopt and raise chicks that are not their own, and “stepmothering” occurs when females pair with a male that has lost his mate; foster-parenting also occurs in Kittiwakes (where about 8 percent of all chicks are adopted). In addition, many birds do not reproduce or do so only rarely: 30—40 percent of adult Western Gulls breed only once or twice in their lifetimes, and do not successfully raise any offspring, while 5 percent of all Kittiwakes that attempt to nest do not raise any young during their lives (and nearly two-thirds of all Kittiwakes never produce any offspring, usually because they die before breeding). Female Western Gulls that breed less often (or defer breeding until later in life) actually have higher survival rates than birds that reproduce more frequently. In Kittiwakes, nonbreeding birds form their own flocks or CLUBS on the outskirts of the breeding colonies. Western Gulls in heterosexual pairs also sometimes engage in nonprocreative sexual behaviors, such as REVERSE mounting (where the female mounts the male, typically without genital contact).

Some male Western Gulls are promiscuous, attempting to copulate with females other than their mates (usually birds on neighboring territories), although they are frequently unsuccessful. Occasionally a male will behave aggressively toward a female he has just mated with (nonmonogamously) and may even attack and kill her. Overall, more than 40 percent of aggressive incidents occur between members of the opposite sex. These include females defending themselves against promiscuous males, males attacking neighboring females that are courting them, and territorial disputes. Females may also refuse to copulate with their own mates, either by not allowing them to mount or by walking out from under them during mating. Some pairs, however, begin copulating even before the female’s fertile period; this also occurs in Kittiwakes, and many copulations in this species do not involve genital contact (more than 30 percent). In Kittiwakes, 15—27 percent of all heterosexual copulations are harassed and interrupted by other males. Occasionally, adult Western Gulls are violent toward chicks, who may be attacked and even killed if left alone by their parents. Kittiwake parents (especially inexperienced ones) sometimes neglect their chicks (e.g., starving them), and birds may also attack or toss their own or other parents’ chicks off cliffs. In fact, many adoptions and chick deaths in both species result from youngsters deserting or “running away” from their biological families as a result of neglect or direct attack. As many as a third of all Kittiwake chicks in some colonies abandon or are driven from their own nests. In addition, adults of both species may eat unattended eggs belonging to other parents.

*asterisked references discuss homosexuality/transgender

*Baird, P. H. (1994) “Black-legged Kittiwake (Rissa tridactyla).” In A. Poole, P. Stettenheim, and F. Gill, eds., The Birds of North America: Life Histories for the 21st Century, no. 92. Philadelphia: Academy of Natural Sciences; Washington, D.C.: American Ornithologists’ Union.

Carter, L. R., and L. B. Spear (1986) “Costs of Adoption in Western Gulls.” Condor 88:253—56.

Chardine, J. W. (1987) “The Influence of Pair-Status on the Breeding Behavior of the Kittiwake Rissa tridactyla Before Egg-Laying.” Ibis 129:515—26.

———((1986) “Interference of Copulation in a Colony of Marked Black-legged Kittiwakes.” Canadian Journal of Zoology 64:1416—21.

*Conover, M. R. (1984) “Occurrence of Supernormal Clutches in the Laridae.” Wilson Bulletin 96:249—67.

*Coulson, J. C., and C. S. Thomas (1985) “Changes in the Biology of the Kittiwake Rissa tridactyla: A 31 Year Study of a Breeding Colony.” Journal of Animal Ecology 54:9—26.

———(1983) “Mate Choice in the Kittiwake Gull.” In P. Bateson, ed., Mate Choice, pp. 361—76. Cambridge: Cambridge University Press.

Coulson, J. C., and E. White (1958) “The Effect of Age on the Breeding Biology of the Kittiwake Rissa tridactyla.” Ibis 100:40-51.

Cullen, E. (1957) “Adaptations in the Kittiwake to Cliff-Nesting.” Ibis 99:275—302.

*Fry, D. M., C. K. Toone, S. M. Speich, and R. J. Peard (1987) “Sex Ratio Skew and Breeding Patterns of Gulls: Demographic Toxicological Considerations.” Studies in Avian Biology 10:26—43.

Hand, J. L. (1986) “Territory Defense and Associated Vocalizations of Western Gulls.” Journal of Field Ornithology 57:1—15.

*———(1980) “Nesting Success of Western Gulls on Bird Rock, Santa Catalina Island, California.” In D. M. Power, ed., The California Islands: Proceedings of a Multidisciplinary Symposium, pp. 467-73. Santa Barbara: Santa Barbara Museum of Natural History.

*Hayward, J. L., and M. Fry (1993) “The Odd Couples/The Rest of the Story.” Living Bird 12:16—19.

*Hunt, G. L., Jr. (1980) “Mate Selection and Mating Systems in Seabirds.” In J. Burger, B. L. Olla, and H. E. Winn, eds., Behavior of Marine Mammals, vol. 4, pp. 113—51. New York: Plenum Press.

*Hunt, G. L., Jr., and M. W. Hunt (1977) “Female-Female Pairing in Western Gulls (Larus occidentalis) in Southern California.” Science 196:1466—67.

*Hunt, G. L., Jr., A. L. Newman, M. H. Warner, J. C. Wingfield, and J. Kaiwi (1984) “Comparative Behavior of Male-Female and Female-Female Pairs Among Western Gulls Prior to Egg-Laying.” Condor 86:157—62.

*Hunt, G. L., J. C. Wingfield, A.L. Newman, and D. S. Farner (1980) “Sex Ratio of Western Gulls on Santa Barbara Island, California.” Auk 97:473—79.

Paludan, K. (1955) “Some Behavior Patterns of Rissa tridactyla.” Videnskabelige Meddelelser fra Dansk naturhistorisk Forening 117:1—21.

Pierotti, R. J. (1991) “Infanticide versus Adoption: An Intergenerational Conflict.” American Naturalist 138:1140—58.

*———(1981) “Male and Female Parental Roles in the Western Gull Under Different Environmental Conditions.” Auk 98:532—49.

———(1980) “Spite and Altruism in Gulls.” American Naturalist 115:290—300.

*Pierotti, R. J., and C. A. Annett (1995) “Western Gull (Larus occidentalis).” In A. Poole and F. Gill, eds., The Birds of North America: Life Histories for the 21st Century, no. 174. Philadelphia: Academy of Natural Sciences; Washington, D.C.: American Ornithologists’ Union.

Pierotti, R. J., and E. C. Murphy (1987) “Intergenerational Conflicts in Gulls.” Animal Behavior 35:435—44.

Pyle, P., N. Nur, W. J. Sydeman, and S.D. Emslie (1997) “Cost of Reproduction and the Evolution of Deferred Breeding in the Western Gull.” Behavioral Ecology 8:140—47.

Roberts, B. D., and S. A. Hatch (1994) “Chick Movements and Adoption in a Colony of Black-legged Kittiwakes.” Wilson Bulletin 106:289—98.

Thomas, C. S., and J. C. Coulson (1988) “Reproductive Success of Kittiwake Gulls, Rissa tridactyla.” In T. H. Clutton-Brock, ed., Reproductive Success: Studies of Individual Variation in Contrasting Breeding Systems, pp. 251—62. Chicago and London: University of Chicago Press.

*Wingfield, J. C., A. L. Newman, G. L. Hunt, Jr., and D. S. Farner (1982) “Endocrine Aspects of Female-Female Pairings in the Western Gull, Larus occidentalis wymani.” Animal Behavior 30:9—22.

*Wingfield, J. C., A. L. Newman, M. W. Hunt, G. L. Hunt, Jr., and D. Farner (1980) “The Origin of Homosexual Pairing of Female Western Gulls (Larus occidentalis wymani) on Santa Barbara Island.” In D. M. Power, ed., The California Islands: Proceedings of a Multidisciplinary Symposium, pp. 461—66. Santa Barbara, Calif.: Santa Barbara Museum of Natural History.

Silver and Herring Gulls are usually found in flocks of several hundreds or thousands; they generally form monogamous pair-bonds and nest in colonies containing anywhere from several hundred to tens of thousands of nests.

Behavioral Expression: In both Silver and Herring Gulls, females sometimes form lesbian pairs while males occasionally participate in homosexual mountings. Female pairs may develop between birds who were previously paired to a male, or they may involve birds who have never been paired before. In some cases, single, nonbreeding Herring Gull females visit the territory of a heterosexual pair and court the female, for example by performing HEAD-TOSSING, in which the head is hunched down and then repeatedly flicked upward. The heterosexually paired birds usually respond aggressively, but sometimes this behavior leads to a homosexual pairing the following season. Like heterosexual pairs, homosexual bonds are usually long-lasting and renewed each year: of those Herring Gull females in homosexual pairs that return to the same breeding grounds, 92 percent pair with the same female (compared to 93 percent of birds in heterosexual pairs). Of those that divorce, some remain single while others find a new (female) mate.

Females in same-sex pairs usually build nests and lay eggs. Silver Gull homosexual females generally begin nesting at a younger age than heterosexual females: females paired to other females start on average about a year earlier than females paired to males, and 11 percent of homosexual females begin nesting when they are two years old (heterosexual females never begin this early). Since both females lay eggs, nests belonging to same-sex pairs often have double or more the number of eggs found in nests of heterosexual pairs. These SUPERNORMAL CLUTCHES contain 4 or more eggs in Silver Gulls (compared to 2 eggs for male-female pairs) and 5—7 eggs in Herring Gulls (compared to 3 eggs for heterosexual pairs). Females sometimes mate nonmonogamously with males—or are raped by them (see below)—while still remaining paired to their female partner. Consequently, some of the eggs laid by female pairs are fertile—about a third in Silver Gulls, and 4—30 percent in Herring Gulls. Homosexual parents often successfully hatch these eggs and raise the chicks. Approximately 3—4 percent of all Silver Gull chicks are raised by same-sex pairs, and a further 9 percent of chicks are raised by male-female pairs in which the mother is bisexual. Overall, 7 percent of birds that go on to become breeding adults in this species come from families with two female parents. However, homosexual and bisexual females generally produce fewer offspring during their lifetimes than do heterosexual females.

In both Silver and Herring Gulls, males in heterosexual pairs often try to copulate with birds other than their mates, and in some cases they mount other males. Like females who are mounted by birds other than their mate, male Herring Gulls may respond aggressively to another male’s mounting them.

Frequency: About 6 percent of all pair-bonds in Silver Gulls are homosexual, while nesting attempts by female pairs occur in approximately 12 percent of all breeding seasons. In some populations of Herring Gulls, nearly 3 percent of the pairs are homosexual, while in other populations they are much less frequent, about 1 in every 360 pairs. In addition, approximately 2 percent of courtship behavior by unpaired females interacting with heterosexual pairs is directed toward the female partner. Male homosexual mountings account for 10 percent of the nonmonogamous copulations in Silver Gulls, and 2 percent of the total number of copulations; they are probably much less common in Herring Gulls.

Orientation: In Silver Gulls, 21 percent of females pair with another female at least once in their lifetimes; 10 percent are exclusively lesbian, mating only with other females during their lives, while 11 percent are (sequentially) bisexual, pairing with both males and females. In one study of Herring Gull homosexual pairs, six out of eight females had been in heterosexual pairs the previous year and formed same-sex bonds with each other when their male mates did not return. Of the remaining birds, one paired with a female after her male partner re-paired with another female, while the other had been a single nonbreeder prior to developing a same-sex pair-bond. In addition, female Herring Gulls may show a “preference” for homosexual pairings, since they sometimes re-pair with another female following the breakup of a same-sex bond. In both species, some females in homosexual pairs copulate with males in order to fertilize their eggs, still retaining their primary homosexual bond. Males that initiate homosexual mountings, while functionally bisexual, are probably primarily heterosexually oriented, since they are usually paired to females and rarely engage in same-sex behavior.

Large numbers of nonreproducing birds are found in both Silver Gulls and Herring Gulls. About half of adult females and 14 percent of males are nonbreeders in some populations of Silver Gulls; more than three-quarters of all birds die before they reproduce, and 85 percent or more never successfully procreate. Many females that do reproduce nevertheless have extended periods of nonbreeding, up to 16 years in some cases. And about a third of females that lose their mates (through divorce or death) never breed again, sometimes living a further decade as single birds. In Herring Gulls, 4–12 percent of males and one-third to two-thirds of females in some populations are nonbreeders; in other populations, more than a third of all birds do not reproduce in any given year. Two distinct types of nonbreeding females occur in this species: FLOATERS, who are truly single and do not consistently associate with any particular gulls, and SECONDARY FEMALES, who maintain a persistent association with a mated heterosexual pair and even help them defend their territory and raise their young (although they themselves do not breed). Herring Gulls and Silver Gulls also sometimes form polygamous trios, in which the two females are both pair-bonded to one male but not to each other. They often build a “double nest” with two cups in which they both lay eggs.

Several other variant family and pairing arrangements are found in these species. About 5—10 percent of Herring Gull pairs adopt chicks, sometimes even from other species such as the lesser black-backed gull (Larus fuscus). Herring Gulls occasionally form pair-bonds with adults of this and other gull species as well. Foster parents usually also have young of their own, while some adopted chicks are cared for by more than one foster family simultaneously. Adoption also occasionally occurs in Silver Gulls. In addition, Herring Gulls sometimes form CRÈCHES, in which several adults pool their youngsters and take turns guarding and feeding them. Although most heterosexual pairs are long-lasting, divorce occurs in about 3—7 percent of Herring Gull pairs and 5—10 percent of Silver Gull pairs. Some Silver Gulls have up to seven different mates over their lives, but about a third have only one partner. In addition, many pair-bonds are nonmonogamous: more than 20 percent of all copulations in Silver Gulls are between nonmates, and more than three-quarters of females and one-third of males are “unfaithful.”

Most promiscuous copulations in Silver Gulls are nonreproductive: 11 percent involve incubating (nonfertilizable) females, and many are actually “rapes” or forced copulations in which the female is not a willing participant. As a result, only 7 percent of such matings involve genital contact. Many within-pair copulations are also nonprocreative: more than 30 percent occur during times when the female cannot be fertilized (such as too early before egg laying), and more than half do not involve genital contact or sperm transfer. In addition, about 9 percent of copulations between pair members are forced by the male on the female. Several forms of heterosexual family abuse and adult-juvenile violence have also been documented in Herring Gulls. Males sometimes incestuously mount their own chicks and have even been seen breaking and eating their own eggs. In addition, chicks in both species are often pecked at, pummeled, thrown, shaken, and even killed (and occasionally cannibalized) by other adults when they stray away from home. Among Herring Gulls, being eaten by other Gulls (and sometimes even by one’s parents) can be a significant mortality factor: in one colony, a quarter of chick deaths—more than 300 youngsters—were the result of cannibalism.

*asterisked references discuss homosexuality/transgender

Burger, J., and M. Gochfeld (1981) “Unequal Sex Ratios and Their Consequences in Herring Gulls.” Behavioral Ecology and Sociobiology 8:125-28.

Calladine, J., and M. P. Harris (1997) “Intermittent Breeding in the Herring Gull Larus argentatus and the Lesser Black-backed Gull Larus fuscus.” Ibis 139:259—63.

Chardine, J. W., and R. D. Morris (1983) “Herring Gull Males Eat Their Own Eggs.” Wilson Bulletin 95:477—78.

*Fitch, M. A. (1979) “Monogamy, Polygamy, and Female-Female Pairs in Herring Gulls.” Proceedings of the Colonial Waterbird Group 3:44—48.

Fitch, M. A., and G. W. Shugart (1984) “Requirements for a Mixed Reproductive Strategy in Avian Species.” American Naturalist 124:116—26.

———(1983) “Comparative Biology and Behavior of Monogamous Pairs and One Male—Two Female Trios of Herring Gulls.” Behavioral Ecology and Sociobiology 14:1—7.

*Goethe, F. (1937) “Beobachtungen und Untersuchungen zur Biologie der Silbermowe (Larus a. argentatus Pontopp.) auf der Vogelinsel Memmerstand [Observations and Investigations on the Biology of the Herring Gull on Bird Island, Memmerstand].” Journal für Ornithologie 85:1—119.

Holley, A. J. F. (1981) “Naturally Arising Adoption in the Herring Gull.” Animal Behavior 29:302—3.

MacRoberts, M. H. (1973) “Extramarital Courting in Lesser Black-backed and Herring Gulls.” Zeitschrift für Tierpsychologie 32:62—74.

*Mills, J. A. (1994) “Extra-Pair Copulations in the Red-billed Gull: Females with High-Quality, Attentive Males Resist.” Behavior 128:41—64.

*———(1991) “Lifetime Production in the Red-billed Gull.” Acta XX Congressus Internationalis Ornithologici, Christchurch, New Zealand (Proceedings of the 20th International Ornithological Congress), vol. 3, pp. 1522—27. Wellington, N.Z.: New Zealand Ornithological Trust Board.

*———(1989) “Red-billed Gull.” In I. Newton, ed., Lifetime Reproduction in Birds, pp. 387-404. London: Academic Press.

———(1973) “The Influence of Age and Pair-Bond on the Breeding Biology of the Red-billed Gull, Larus novaehollandiae scopulinus.” Journal of Animal Ecology 42:147—62.

*Mills, J. A., J. W. Yarrall, and D. A. Mills (1996) “Causes and Consequences of Mate Fidelity in Red-billed Gulls.” In J. M. Black, ed., Partnerships in Birds: The Study of Monogamy, pp. 286-304. Oxford: Oxford University Press.

Nisbet, 1. C. T., and W. H. Drury (1984) “Supernormal Clutches in Herring Gulls in New England.” Condor 86:87—89.

Parsons, J. (1971) “Cannibalism in Herring Gulls.” British Birds 64:528—37.

Pierotti, R. J. (1980) “Spite and Altruism in Gulls.” American Naturalist 115:290—300.

Pierotti, R. J., and T. P. Good (1994) “Herring Gull (Larus argentatus).” In A. Poole and F. Gill, eds., The Birds of North America: Life Histories for the 21st Century, no. 124. Philadelphia: Academy of Natural Sciences; Washington, D.C.: American Ornithologists’ Union.

Richards, C. E. (1995) “Attempted Copulation Between Adult and First-Year Herring Gulls.” British Birds 88:226.

*Shugart, G. W. (1980) “Frequency and Distribution of Polygyny in Great Lakes Herring Gulls in 1978.” Condor 82:426—29.

*Shugart, G. W., M. A. Fitch, and G. A. Fox (1988) “Female Pairing: A Reproductive Strategy for Herring Gulls?” Condor 90:933—35.

*———(1987) “Female Floaters and Nonbreeding Secondary Females in Herring Gulls.” Condor 89:902—6.

Tasker, C. R., and J. A. Mills (1981) “A Functional Analysis of Courtship Feeding in the Red-billed Gull, Larus novaehollandiae scopulinus.” Behavior 77:221—41.

Wheeler, W. R., and 1. Watson (1963) “The Silver Gull Larus novaehollandiae Stephens.” Emu 63:99—173.

Black-headed Gulls are gregarious, gathering in large flocks throughout most of the year. They form pair-bonds and nest in dense colonies containing up to several thousand pairs.

Behavioral Expression: Male homosexual pairs are found in Black-headed Gulls, and they are usually initiated with the same courtship behaviors seen in heterosexual pairs. At the beginning of the mating season, one male lands on the territory of another male who is performing an ADVERTISEMENT DISPLAY, consisting of a series of loud, rasping screams sounding like kreeeee kreeeee… (the LONG CALL). This is made while the bird assumes an OBLIQUE-POSTURE (head extended forward and upward with the bill horizontal). The displaying male may also approach the other male in the FORWARD-POSTURE, in which the head is lowered and held level with the rest of the body, neck kinked, and tail spread. Over the next several weeks, as their pair-bond develops, the two males perform frequent MEETING CEREMONIES, stylized courtship interactions that include many of the same movements seen in the advertisement display, combined with HEAD-FLAGGING, in which the two birds alternately turn their heads toward and away from their partner. The two birds sometimes also perform COURTSHIP-FEEDING, in which one male ritually begs the other for food, who may respond by regurgitating a ceremonial food “offering” for his mate. Males in homosexual pairs generally perform meeting ceremonies more frequently than birds in heterosexual pairs; their long-calling and head-flagging rates are intermediate between those of males and females in heterosexual pairs, while they generally beg and courtship-feed less than either males or females in opposite-sex pairs.

Once their pair-bond is established, male partners may also engage in sexual behavior. This can involve one male simply mounting the other, but in other cases it consists of full copulation with repeated genital contacts between the two males. In some homosexual couples, both males take turns mounting each other, although in most instances only one partner is the mounter and the other is the mountee. Male couples usually build a nest together, with both birds contributing to its construction. Occasionally the nest is built entirely by one partner (as in heterosexual pairs, where usually only the male builds the nest). Most homosexual pairs are unable to obtain eggs, although it is possible that some may “adopt” eggs abandoned by heterosexual pairs. In addition, females in this species occasionally lay eggs in other birds’ nests, so male pairs could acquire eggs in this way as well. When provided with “foster eggs” in captivity, homosexual pairs faithfully incubate and hatch them and in some cases even successfully raise the chicks together.

In addition to monogamous homosexual pairs, several other variations of same-sex bonding occur. About 25 percent of males in homosexual associations are polygamous (comparable to rates for males in heterosexual associations). Such males form trios, bonding either with two males, or with one male and one female (in one case, a same-sex trio later developed into a bisexual “quartet” when a female joined them). Some male couples are nonmonogamous, in that one or both partners court and even copulate with outside partners of either sex. Homosexual pairings are generally not as long-lasting as heterosexual ones: an average of 15 percent of same-sex bonds last for at least two consecutive seasons, compared to 56 percent of heterosexual bonds. Nevertheless, many homosexual bonds are strong, and partners will maintain their attachment to their mate even if they are forcibly separated from one another, resuming their partnership once reunited. Males also frequently engage in serial pairing, forming bonds with three to four different partners over time (both males and females). Sometimes, the permutations of all these different possibilities can be dizzying—in one case, a male who had been in a homosexual couple later paired with a female, during which time he engaged in promiscuous, “incestuous” courtship and mating with a heterosexually paired female that he had previously foster-parented with his male partner!

In addition to a pattern of homosexual pair-bonding, male Black-headed Gulls in heterosexual pairs sometimes copulate with birds other than their mate, including other males. These nonmonogamous copulations are usually “forced” in the sense that the mounted bird does not solicit the sexual activity and usually vigorously pecks at the male and drives him away. Often a promiscuous male will hover over another male, trying unsuccessfully to mount, although in some cases a male may be able to mount and remain on the other male for as long as five minutes (albeit without any genital contact taking place). Sometimes a promiscuous mounting leads to a same-sex pair-bond: one heterosexually paired bird who mounted both partners of a heterosexual couple, for example, formed a homosexual bond the next year with the male partner of that couple.

Frequency: Male couples that court, mate, and nest together have been documented in wild populations, although their overall incidence is not known. In captivity, homosexual pairs can account for 16–18 percent of all bonds, while two out of 9 promiscuous mountings (22 percent) in one study were homosexual. At the height of courtship, individual males in homosexual pairs may perform displays such as ceremonial encounters or long-calling as often as 40–60 or more times an hour.

Orientation: In a study of Black-headed Gulls in captivity, 22 percent of the males formed bonds only with other males, 15 percent formed bonds with both males and females, while 63 percent bonded only with members of the opposite sex. In addition, layered on top of these patterns of pair-bonding are instances of nonmonogamous, bisexual courtship and sexual activity—often same-sex for heterosexually paired birds, and opposite-sex for homosexually paired birds. Furthermore, younger males appear to have a preference for homosexual pairing that declines somewhat as the birds get older: 55–60 percent of bonds are same-sex among one-to-two-year-olds, compared to 30–45 percent in two-to-five-year-olds, and 20 percent in five-to-eight-year-olds. In addition, many males may have a “latent” capacity for bisexuality, being able to form same-sex bonds when females are not available.

Most of the variations on long-term, monogamous pair-bonds seen in homosexual contexts also occur in heterosexual associations among Black-headed Gulls. Promiscuous courtships and copulations can be entirely heterosexual: some females court males other than their mate, while males may try to rape females they aren’t paired with (within-pair copulations are also sometimes accompanied by aggression or unwillingness between partners). As noted above, divorce (changing of partners between breeding seasons) occurs fairly frequently in opposite-sex pairs. In addition, mate-switching within the breeding season is quite common—more than half of all males form brief liaisons with females that last a few days, mating with up to seven different partners. Polygamous trios also occur in this species: occasionally, a female will join a mated pair, bond with the male, and help them raise their young, although she herself does not breed. Some females lay eggs in the territories of other heterosexual couples, who may then adopt those eggs as their own; adoption of chicks also occurs. A number of nonreproductive sexual behaviors are also characteristic of this species. Heterosexual mounting often does not involve mutual genital contact, females sometimes mount males (REVERSE mounts), and heterosexual pairs occasionally copulate during incubation or after the hatching of their eggs. In addition, males occasionally try to mate with chicks (including their own), who may be only a few days old; juveniles also mount each other. Young birds are also subjected to abuse when they cross territories belonging to other heterosexual pairs, who may attack and even kill them; cannibalism has also been reported in this species.

*asterisked references discuss homosexuality/transgender

Axell, H. E. (1969) “Copulatory Behavior of Juvenile Black-headed Gull.” British Birds 62:445.

Beer, C. G. (1963) “Incubation and Nest-Building Behavior of Black-headed Gulls IV: Nest-Building in the Laying and Incubation Periods.” Behavior 21:155–76.

*Kharitonov, S. P., and V. A. Zubakin (1984) “Protsess formirovania par u ozyornykh chaek [Pair-bonding in the Black-headed Gull].” Zoologichesky Zhurnal 63:95–104.

Kirkman, F. B. (1937) Bird Behavior. London: Nelson.

Moynihan, M. (1955) Some Aspects of Reproductive Behavior in the Black-headed Gull (Larus ridibundus ridibundus L.) and Related Species. Behavior Supplement 4. Leiden: E. J. Brill.

*van Rhijn, J. (1985) “Black-headed Gull or Black-headed Girl? On the Advantage of Concealing Sex by Gulls and Other Colonial Birds.” Netherlands Journal of Zoology 35:87–102.

*van Rhijn, J., and T. Groothuis (1987) “On the Mechanism of Mate Selection in Black-headed Gulls.” Behavior 100:134–69.

*———(1985) “Biparental Care and the Basis for Alternative Bond-Types Among Gulls, with Special Reference to Black-headed Gulls.” Ardea 73:159—74.

Laughing Gulls are highly social and gregarious, forming large flocks at all times of the year, while Ivory Gulls tend to be more solitary or gather in smaller flocks. Their mating system involves pair-bonding, and birds nest in colonies that contain a few dozen pairs in Ivories and several hundred to as many as 25,000 pairs in Laughing Gulls.

Behavioral Expression: Pair-bonds sometimes develop between two male Laughing Gulls, including sexual and parenting activities as well as unique courtship and territorial behaviors. A homosexual bond begins when two males KEEP COMPANY: in this courtship activity, they approach and circle each other while performing elegant FACING-AWAY or HEAD-TOSS displays (in which the birds ritually turn their heads in opposite directions or flick them upward from a hunched posture). This is followed by a period of resting together somewhat apart from the other Gulls. Two males may even begin courting in this way early in the breeding season before heterosexual couples have started their courtships. Male partners also COURTSHIP-FEED each other, in which they present one another with a symbolic “gift” of food. Although this behavior is also found in opposite-sex courtship, in homosexual pairs it has a unique feature. The two males pass the food back and forth between them many times before one or both of them eat it, whereas in heterosexual pairs, the male presents the food to the female, who immediately eats it. Pair-bonded males also mount each other, although genital contact usually does not occur. Mounting is generally not one-sided, although one male may prefer being mounter or mountee more than the other. In one male couple, for example, one partner mounted the other nine times over the season while the other mounted him three times. Homosexual (as well as heterosexual) mounts may be accompanied by distinctive staccato COPULATION CALLS by the mounting male, sounding like kakakakakaka. Both males in homosexual pairs build a nest together; in captivity, pairs take turns incubating eggs when these are supplied to the couple. After the eggs hatch, both males share parenting duties such as feeding and protecting the chicks and are able to successfully raise the youngsters.

Male couples can be quite aggressive, repeatedly intruding on neighboring territories of heterosexual pairs, who try, often unsuccessfully, to deter them. During these “raids,” the males may engage in sexual behavior with one another, or they may even try to court or mount a neighboring female. Similar territorial invasions are sometimes also made by single males, heterosexually paired males, or “coalitions” of two males that are not necessarily bonded or sexually involved with each other. In these cases, the intruding males often mount the male partner of the heterosexual pair they encounter, sometimes in full view of his incubating female mate (who is usually indifferent). If there are two intruding males, they may take turns in homosexual mounts on the male of the pair. The mounted male usually responds by violently shaking, pecking, and fluttering in order to dislodge the mounter—who may end up getting grabbed by the beak and tossed over his head. Sometimes an intruding male will even mount a male who is copulating with his female partner, creating a three-bird “pile-up.”

A similar sort of forced homosexual mounting occurs in Ivory Gulls. Males approach incubating birds whose partners are away from the nest. The intruding male carries a distraction “gift” of nesting material—usually a lump of moss—and circles the nest. He then suddenly jumps on the back of the incubating bird—even if it is a male—and attempts to copulate. As in Black-headed Gulls, the mounted bird usually responds violently.

Frequency: In a zoo population of Laughing Gulls, one pair-bond out of a total of four was between two males; the incidence of homosexual pairs in wild birds is not known, although homosexual mounts by intruding males have been documented in wild birds. Forced mountings on incubating Ivory Gulls are very frequent in some colonies in the wild, although it is not known specifically what proportion are same-sex.

Orientation: Male Laughing Gulls in homosexual pairs may be simultaneously bisexual, since they sometimes court and mount females while maintaining their primary same-sex pair-bond. Intruding males that participate in homosexual mounts may also be bisexual if they are paired to a female, although unpaired males engage in this activity as well. Such males also mount females during their intrusions, but in many cases they are clearly “targeting” the male partner. For example, they may completely ignore the female as she sits incubating, or they may remain mounted on the male after he dismounts from the female during a “pile-up,” again ignoring the female once she becomes “available.” Most males that are subject to intruding mounts like this probably have a primary heterosexual orientation, since they usually react aggressively to any homosexual activity. However, it must be remembered that females with a primary heterosexual bond also react violently to mounts by intruding males.

Female Laughing Gulls occasionally “adopt” and incubate eggs laid in their nests by other females, including females of other species such as clapper rails (Rallus longirostris). Heterosexual pairs in this species also have very high copulation rates, mating as often as nine times a day prior to egg laying. As noted above, forced copulation attempts are common in Laughing and Ivory Gulls as well, and many of these are heterosexual. About 30 percent of male Laughing Gull territorial intruders attempt to rape females, although such attacks are usually thwarted by the female and her mate; in addition, most are directed toward incubating females and hence are nonreproductive. Abuse and violence by heterosexual parents against chicks also occur in both species. During raids by predators such as snowy owls (Nyctea scandiaca), a pandemonium often develops in Ivory Gull breeding colonies, and groups of adult Gulls mob terrified chicks and sometimes even attack and kill them. The adults also puncture eggs and eat them; eggs containing fully developed embryos about to hatch are smashed and the yolk sac is eaten, but the down-covered embryo is discarded. Laughing Gulls also occasionally attack, kill, and even eat chicks (as well as eggs) on neighboring territories; cannibalism appears to be limited to a few individuals in dense colonies who repeatedly perform this behavior.

*asterisked references discuss homosexuality/transgender

Bateson, P. P. G., and R. C. Plowright (1959a) “The Breeding Biology of the Ivory Gull in Spitsbergen.” British Birds 52:105–14.

———(1959b) “Some Aspects of the Reproductive Behavior of the Ivory Gull.” Ardea 47:157–76.

Burger, J. (1996) “Laughing Gull (Larus atricilla).” In A. Poole and F. Gill, eds., The Birds of North America: Life Histories for the 21st Century, no. 225. Philadelphia: Academy of Natural Sciences; Washington, D.C.: American Ornithologists’ Union.

———(1976) “Daily and Seasonal Activity Patterns in Breeding Laughing Gulls.” Auk 93:308–23.

Burger, J., and C. G. Beer (1975) “Territoriality in the Laughing Gull (L. atricilla).” Behavior 55:301–20.

Hand, J. L. (1985) “Egalitarian Resolution of Social Conflicts: A Study of Pair-bonded Gulls in Nest Duty and Feeding Contexts.” Zeitschrift für Tierpsychologie 70:123–47.

*———(1981) “Sociobiological Implications of Unusual Sexual Behaviors of Gulls: The Genotype/Behavioral Phenotype Problem.” Ethology and Sociobiology 2:135–45.

*Haney, J. C., and S. D. MacDonald (1995) “Ivory Gull (Pagophila eburnea).” In A. Poole and F. Gill, eds., The Birds of North America: Life Histories for the 21st Century, no. 175. Philadelphia: Academy of Natural Sciences; Washington, D.C.: American Ornithologists’ Union.

MacDonald, S. D. (1976) “Phantoms of the Polar Pack-Ice.” Audubon 78:2–19.

*Noble, G. K., and M. Wurm (1943) “The Social Behavior of the Laughing Gull.” Annals of the New York Academy of Sciences 45:179–220.

Segrè, A., J. P. Hailman, and C. G. Beer (1968) “Complex Interactions Between Clapper Rails and Laughing Gulls.” Wilson Bulletin 80:213–19.

During the mating season, Caspian and Roseate Terns usually congregate in large colonies which may contain up to 500 pairs in Caspians and several thousand in Roseates. The typical social unit is the monogamous mated pair. Outside of the mating season, Terns are less gregarious and are usually found alone or in small groups.

Behavioral Expression: In both Caspian and Roseate Terns, two females may pair with each other, associating together the way a male-female pair does. Usually such homosexual pairs also build nests and lay eggs. Since both females typically lay, the result is a SUPERNORMAL CLUTCH containing up to twice the number of eggs found in nests of heterosexual pairs—4—6 eggs for Caspian homosexual pairs, and 3—5 eggs for Roseates. Both females take turns incubating the eggs (as do mates in heterosexual pairs). Sometimes the eggs are infertile, but in many cases they do hatch. There are several possible sources for fertile eggs in same-sex pairs: for example, one or both females may copulate with a male while still remaining bonded to her female mate. In addition, it appears that females in some populations occasionally “steal” eggs from others’ nests, sometimes transferring eggs from as many as three other nests into their own. Approximately 13 percent of supernormal clutches in some locations have at least one “stolen” egg in them, so it is likely that at least some females in homosexual pairs utilize this strategy. Once the eggs hatch, both females share parenting duties (as do partners in heterosexual pairs), which include feeding the young, protecting the chicks from predators, sheltering them against the sun, and defending the nesting territory.

Frequency: In Caspian Terns, 3–6 percent of pairs are homosexual; in Roseates, about 5 percent of chicks are tended by female pairs in some populations.

Orientation: Females in homosexual pairs that copulate with males in order to fertilize their eggs are functionally bisexual, although they retain their primary bond with the other female. Other female pairs may be exclusively homosexual for the duration of their pair-bond, since they do not lay fertile eggs. Some females are also sequentially bisexual, alternating between male and female partners in different breeding seasons.

Terns occasionally “steal” eggs from other clutches, as described above for homosexual pairs; birds in heterosexual pairs probably do so, since some nests with transferred eggs do not have supernormal clutches. In addition, female Roseate Terns sometimes lay eggs in nests other than their own, resulting in “super-supernormal clutches.” In one colony, for example, about 1 percent of the nests had 7 eggs—more than twice the number found even in supernormal clutches. Most such nests appear to belong to heterosexual pairs. Caspian Terns also have a high divorce rate: more than half of all male-female pairs do not last more than one season. Female Roseate Terns sometimes successfully raise chicks as a single parent when their male partner dies. As in many Gulls, infanticide and aggression toward chicks also occur in some Tern species. Caspian Terns, for example, often violently attack—and may even kill—chicks that wander onto their territories and may break eggs during their squabbles as well. Caspian Terns also commonly form CRÈCHES, dense herds of chicks attended by a few adults who watch over them while their parents are away foraging.

*asterisked references discuss homosexuality/transgender

*Conover, M. R. (1983) “Female-Female Pairings in Caspian Terns.” Condor 85:346–49.

Cramp, S., ed. (1985) “Caspian Tern (Sterna caspia)” and “Roseate Tern (Sterna dougallii).” In Handbook of the Birds of Europe, the Middle East, and North Africa, vol. 4, pp. 17–27, 62–71. Oxford: Oxford University Press.

Cuthbert, F. J. (1985) “Mate Retention in Caspian Terns.” Condor 87:74–78.

*Gochfeld, M., and J. Burger (1996) “Sternidae (Terns).” In J. del Hoyo, A. Elliott, and J. Sargatal, eds., Handbook of the Birds of the World, vol. 3: Hoatzin to Auks, pp. 624–67. Barcelona: Lynx Edicións.

*Hatch, J. J. (1995) Personal communication.

*———(1993) “Parental Behavior of Roseate Terns: Comparisons of Male-Female and Multi-Female Groups.” Colonial Waterbird Society Bulletin 17:43.

Milon, P. (1950) “Quelques observations sur la nidification des sternes dans les eaux de Madagascar [Some Observations on the Nesting of Terns in the Waters of Madagascar].” Ibis 92:553.

*Nisbet, I. C. T. (1989) “The Roseate Tern.” In W. J. Chandler, ed., Audubon Wildlife Report 1989/1990, pp. 478–97. San Diego: Academic Press.

*Nisbet, 1. C. T., J. A. Spendelow, J. S. Hatfield, J. M. Zingo, and G. A. Gough (1998) “Variations in Growth of Roseate Tern Chicks: II. Early Growth as an Index of Parental Quality,” Condor 100:305–15.

Penland, S. T. (1984) “An Alternative Origin of Supernormal Clutches in Caspian Terns.” Condor 86:496.

*Sabo, T. J., R. Kessell, J. L. Halverson, I. C. T. Nisbet, and J. J. Hatch (1994) “PCR-Based Method for Sexing Roseate Terns (Sterna dougallii).” Auk 111:1023–27.

Shealer, D. A., and J. G. Zurovchak (1995) “Three Extremely Large Clutches of Roseate Tern Eggs in the Caribbean.” Colonial Waterbirds 18:105–7.

*Spendelow, J. A., and J. M. Zingo (1997) “Female Roseate Tern Fledges a Chick Following the Death of Her Mate During the Incubation Period.” Colonial Waterbirds 20:552–55.

COTINGAS, MANAKINS, AND OTHERS

The spectacularly plumed Guianan Cock-of-the-Rock has what is known as a LEK social and mating system: males inhabit individual territories, usually clustered in the same area, which are used for display and courtship. Each display “court” consists of a cleared area on the forest floor and surrounding perches. Territories are maintained year-round, but courtship and mating occur only from late December through April. Females (and in this species, young males) visit these territories to choose which males they want to mate with. Other than this, males and females lead virtually separate lives: males do not participate in any aspect of nesting or parental care and rarely encounter females outside of the breeding season.

Behavioral Expression: Homosexual activity between adult and adolescent males, as well as among adolescent males, is a routine occurrence in Guianan Cock-of-the-Rock. Males court and display to each other, as well as engage in homosexual mounting. A typical homosexual encounter begins when the adult males are perched beside their display courts, each glowing like an orange beacon in the jungle gloom. Both females and adolescent (yearling) males are attracted to the lek, which is carefully situated in the forest to take advantage of the ambient light characteristics of the environment (thereby showing off its owner to his best advantage). The courtship sequence commences with a GREETING DISPLAY: the males begin calling raucously, then each drops to the ground with a thump and begins beating his wings violently, flashing patches of black and white. This often produces a whistling sound as air rushes through the specially modified wing feathers.

This attention-grabbing sequence is followed by the GROUND DISPLAY: each adult male crouches down, fanning out the delicate filaments of his wing coverts, puffing out his chest and rump feathers and erecting his crest, resulting in a spectacular visual effect. By this time an adolescent male who is attracted by the display has landed beside the adult and is hopping about the display court, often crouching in a version of the courtship posture himself. The adult keeps his back toward the younger male at all times but is otherwise motionless, showing off his plumage to its best and inviting the adolescent to mount him. During homosexual copulation, the younger male climbs onto the adult’s back and perches firmly, moving his tail sideways to try to make genital contact. Often the younger male mounts the older male several times in succession, and courtship and display often alternate with mountings. Sometimes males also mount each other in the trees surrounding a display court. Homosexual interactions differ from heterosexual ones in that both participants perform some version of the ground display; also, unlike females, neither male pecks at or touches the other’s rump prior to mounting.

Adolescent males usually visit the display courts of several adult males, although some adults are clearly more “popular” than others because they receive more attention from the younger males. Typically, a yearling has homosexual interactions with anywhere from one to seven different adult males during the mating season. Nor does homosexual activity always involve an adult territory owner and a yearling male: adolescents often mount nonbreeding males who do not have their own display territories and sometimes also mount other adolescent males. Homosexual activity is not separate from heterosexual courtship and copulation, but takes place in the same locations and often while male-female interactions are happening in the vicinity. However, homosexual courtship and mounting often take priority over heterosexual interactions. If an adolescent male approaches an adult who is courting a female, the female usually leaves (or is chased away), and the two males turn their attentions to each other. Moreover, if a female encounters a male who is courting or involved sexually with another male, she usually waits until the adolescent male leaves before approaching the adult.

Frequency: Homosexual activity is very common among Guianan Cock-of-the-Rock: in fact, mountings between males are as frequent as male-female mountings, accounting for nearly half of all copulations. About 10 percent of heterosexual courtships are interrupted by adolescent males visiting the courting male; roughly one out of five of these “interruptions” involves courtship or sexual behavior between males. During the breeding season, homosexual activity may occur daily, and an adolescent male will usually have 6–7 homosexual encounters over the season (although some males engage in homosexual mounting more frequently, 15 or more times over a season).

Orientation: Close to 40 percent of the male population participates in some form of homosexual activity. Depending on his age, a bird that has same-sex interactions may or may not also engage in heterosexual activity. Among adult males (three years or older), nearly a quarter (23 percent) are mounted by other males, and 6 percent of these do not mate or court females at all. In fact, those adults who do not mate heterosexually are often the ones most frequently mounted by younger males. Among yearling males (virtually none of whom mount females), almost two-thirds (64 percent) engage in homosexual activity. Two-year-old males, on the other hand, very rarely engage in homosexual activity. Thus, when birds of all ages are taken into account, nearly 20 percent of the male population at any given time is involved exclusively in homosexuality.

As described above, male and female Guianan Cock-of-the-Rock have essentially no contact with each other outside of the mating season. Even during the breeding season, their interactions are often unfriendly or overtly aggressive. Males frequently harass females by chasing them around the display court and in some cases attempt to forcibly copulate with them. Females struggle violently during these rape attempts and are usually able to get away, but are visibly stressed following such interactions. In fact, only 20 percent of all lek visits by females result in copulation. There is also a significant proportion of nonbreeding individuals in the population: an average of 20 percent of adult males do not have display territories (and thus rarely, if ever, court or mate with females), while nearly two-thirds of territorial males fail to mate each year. Moreover, males are rarely able to acquire their own territories (and therefore court females) before they are three to four years old. In addition, many females who visit the courtship grounds never actually mate with males during the entire breeding season.

*asterisked references discuss homosexuality/transgender

Endler, J. A., and M. Théry (1996) “Interacting Effects of Lek Placement, Display Behavior, Ambient Light, and Color Patterns in Three Neotropical Forest-Dwelling Birds.” American Naturalist 148:421–52.

Gilliard, E. T. (1962) “On the Breeding Behavior of the Cock-of-the-Rock (Aves, Rupicola rupicola).” Bulletin of the American Museum of Natural History 124:31–68.

Trail, P. W. (1989) “Active Mate Choice at Cock-of-the-Rock Leks: Tactics of Sampling and Comparison.” Behavioral Ecology and Sociobiology 25:283–92.

*———(1985a) “A Lek’s Icon: The Courtship Display of a Guianan Cock-of-the-Rock.” American Birds 39:235–40.

———(1985b) “Courtship Disruption Modifies Mate Choice in a Lek-Breeding Bird.” Science 227:778–80.

*———(1983) “Cock-of-the-Rock: Jungle Dandy.” National Geographic Magazine 164:831–39.

*Trail, P. W., and D. L. Koutnik (1986) “Courtship Disruption at the Lek in the Guianan Cock-of-the-Rock.” Ethology 73:197–218.

Calfbird males congregate, eight to ten at a time, on a display area or LEK in the understory of the rain forest canopy. Each lek consists of a central perch occupied by only one male, around which the remaining males cluster. Females (and males) visit the central male during courtship, usually at dawn; mating is polygamous or promiscuous, and females nest and raise the young on their own.

Behavioral Expression: Male Calfbirds sometimes court other males who are attracted to the leks. A homosexual courtship begins when one male approaches the display site in a posture that females also adopt when entering the lek: the body is held in a horizontal position and all of the feathers are sleeked down, including the cowl feathers. He is attracted by the dramatic display of the central male, which consists of a loud, droning MOO call (hence the bird’s name) sounding something like grr-aaa-oooo. While mooing, the displaying male first puffs himself up, fluffing up his cowl feathers, and then sinks back down in a bowing motion while exposing two bright orange feather globes on either side of his tail. The male in horizontal posture gets close to the mooing bird, who may then direct his courtship displays directly at the other male—for example, by hopping closer while mooing intensely, or engaging in ritualized wing-preening. Usually the approaching male is then chased away if he gets too close, and in fact no homosexual copulations have yet been observed in this species. However, heterosexual mating itself is fairly rare (only occurring in 14 percent of dawn courtship visits by females), and displaying males also frequently chase females who approach them. Furthermore, males do sometimes mount or attempt to mount other males outside of the lek, though this may occur in an aggressive context. Calfbirds also typically form “companionships” with each other: the two males perform coordinated courtship displays, almost touching as they perch side by side, while they both moo and bow in precise alternation. In some cases, companions never perform courtship displays without their male partner. Companions also travel together on the lek and may even share a “home” with each other. Calfbirds typically have what is known as a RETREAT, a special location or tree where each male regularly spends time when not on the lek. Display partners sometimes share the same retreat.

Female Calfbirds also develop bonds with one another: the two companions keep each other company while feeding, travel together to and from the lek, and even nest close to each other. This is all the more remarkable considering that there are no heterosexual pair-bonds in this species. Female pairs use a number of distinctive calls to communicate with each other. While feeding together, for example, they maintain contact with soft wark calls. When one female sits on her nest, the other may perch nearby uttering a rasping waaa call regularly for over an hour, perhaps acting as a lookout for her companion. And two females nesting close to each other sometimes communicate with a unique low, growling call that sounds like grewer grewer, which is only heard in this context. Although no same-sex courtship or copulation has yet been observed, females do sometimes perform behaviors that are typically associated with displaying males. For example, one female was seen to call and posture repeatedly in the fashion of a male courting on a lek (though she did this away from the lek, at her nest). Her call was like the first half of the male’s mooing, and she displayed the orange tail ornaments usually seen in the male’s courtship sequence. Her voice was also raspier than other females’, and she built an exceptionally large nest. In addition, females sometimes adopt the male’s characteristic upright and fluffed appearance when they visit the lek.

Frequency: Approximately 1–2 percent of all courtship visits involve one male displaying to another, and all males (except for the central one) have male display partners. Mounting attempts between males occur fairly frequently, but it is not known how prevalent female same-sex activities are.

Orientation: Because only the central male ever copulates with females, the remainder of the male population is effectively involved only in same-sex activities for the duration of the breeding season, whether display companionships or courtship/mounting with other males. The central male, however, displays mostly to females and occasionally to males, so his behavior is bisexual—albeit primarily heterosexual. In addition, in the next breeding season another male may become the central one, so at least some of the males exhibit sequential bisexuality, while the remainder may continue to experience longer periods of more exclusive homosexuality.

As discussed above, the majority of the male population in any given year does not reproduce: only one male (the central one in the lek) ever breeds with a female. Moreover, only 12 percent of females mate during their dawn courtship visits, and heterosexual relations are frequently fraught with difficulty. Copulations are brief, often incomplete, and accompanied by aggression. Females visiting the lek are constantly chased by the noncentral males, while nearly one-third of male-female copulations and more than half of all courtship visits are disrupted and harassed by other Calfbirds.

*asterisked references discuss homosexuality/transgender

*Snow, B. K. (1972) “A Field Study of the Calfbird Perissocephalus tricolor.” Ibis 114:139–62.

———(1961) “Notes on the Behavior of Three Cotingidae.” Auk 78:150-61.

Snow, D. (1982) The Cotingas: Bellbirds, Umbrellabirds, and Other Species. Ithaca: Cornell University Press.

*———(1976) The Web of Adaptation: Bird Studies in the American Tropics. New York: Quadrangle/New York Times Book Co.

*Trail, P. W. (1990) “Why Should Lek-Breeders Be Monomorphic?” Evolution 44:1837–52.

Male Swallow-tailed Manakins form stable, long-term associations of four to six individuals that spend virtually all of their time together; they remain with each other throughout the mating season and usually from year to year as well. These groups display together on traditional courts or LEKS. The mating system is polygamous, with males (and probably also females) copulating with multiple partners, although large numbers of males are nonbreeders. Blue-backed Manakins have a similar social organization.

Behavioral Expression: Male Swallow-tailed Manakins perform an elaborate group courtship ritual, the JUMP DISPLAY. Sometimes this display is directed toward females, sometimes toward yearling or younger adult males (the latter resembling females in their green plumage, but distinct because of their red-orange caps), and less commonly toward another adult male. To begin a homosexual jump display, a group of two to three adult males gathers on a display perch on their lek, lined up side by side, with the (younger) male they are displaying to perched at the head of this row. While uttering squawking notes that resemble a chorus of frogs, the adult males crouch down, quiver their bodies, and shuffle their feet, forming a collective vibrating mass. The courting males then take turns jumping up and hovering in front of the younger male while giving a sharp dik-dik-dik call, landing next to him. As each male jumps, the others slide down the perch toward his former position, repeating the sequence each time to produce a continuous rotation of flying and sliding birds, whose orange-red crowns collectively form a “whirling torch” in front of the courted bird. During this coordinated display, the younger male usually sits motionless in an upright posture. Males also sometimes mount each other and attempt copulation.

A similar revolving courtship display is performed by pairs of male Blue-backed Manakins for a third bird, which is sometimes a younger male. The display begins with a duet between the displaying males in order to attract a potential mate: the two birds perch side by side and utter perfectly synchronized chup calls. Once a younger male arrives, they begin courting him with their CATHERINE WHEEL DISPLAY. Each adult male jumps up alternately and flutters backward, “leapfrogging” over his partner, who moves forward to replace him in a precisely timed sequence that resembles two juggling balls. This is repeated up to 60 times to create a “cartwheel” of flying birds, oriented toward the male being courted, that gradually gets faster and faster. All the while the displaying males utter vibrant nasal or buzzing sounds that resemble the twanging of a Jew’s harp. At the peak of the dancing frenzy, one of the adult males calls sharply and his partner disappears; the first male then begins courting the younger male one-on-one. He crisscrosses his display perch in a buoyant, butterfly-like flight, alighting in front of the other male every once in a while to lower his head, vibrate his wings and opalescent blue back, and display his brilliant red crest with its two extendable horns. During this performance, the younger male crouches and constantly turns to face the older male courting him, sometimes also responding with a similar bouncing “butterfly” flight across the display perch.

Frequency: The overall proportion of courtships or mounts that occur between males is not yet known for either of these species, although they may be relatively infrequent. However, two of three observed “butterfly” courtship displays in a study of Blue-backed Manakins were directed toward males, while in a two-year study of Swallow-tailed Manakins, only ten heterosexual matings were recorded. It is possible, therefore, that same-sex activity represents a sizable proportion of all courtship and/or sexual activity.

Orientation: Only one out of every four to six male Swallow-tailed Manakins displaying on the lek ever copulates with females; thus, a large proportion of males are not involved directly in male-female sexual (mounting) activity, although they do participate in both heterosexual and homosexual courtships. A similar pattern occurs in Blue-backed Manakins.

In addition to significant numbers of nonbreeding males, Swallow-tailed Manakin populations are characterized by several other less-than-optimal heterosexualities. Only about a third of male-female courtships ever result in mating: half of the time, females being courted simply leave, while in the remainder of cases other males disrupt the courtship displays. However, when mating does take place, a female may copulate with the same male up to six times in one visit; the same is also true for Blue-backed Manakins.

*asterisked references discuss homosexuality/transgender

Foster, M. S. (1987) “Delayed Maturation, Neoteny, and Social System Differences in Two Manakins of the Genus Chiroxiphia.” Evolution 41:547–58.

———(1984) “Jewel Bird Jamboree.” Natural History 93(7):54–59.

———(1981) “Cooperative Behavior and Social Organization in the Swallow-tailed Manakin (Chiroxiphia caudata).” Behavioral Ecology and Sociobiology 9:167-77.

Gilliard, E. T. (1959) “Notes on the Courtship Behavior of the Blue-backed Manakin (Chiroxiphia pareola ).” American Museum Novitates 1942:1–19.

*Sick, H. (1967) “Courtship Behavior in the Manakins (Pipridae): A Review.” Living Bird 6:5-22.

*———(1959) “Die Balz der Schmuckvögel (Pipridae) [The Mating Ritual of Jewel Birds].” Journal für Ornithologie 100:269–302.

*Snow, D. W. (1976) The Web of Adaptation: Bird Studies in the American Tropics. New York: Quadrangle/New York Times Book Co.

———(1971) “Social Organization of the Blue-backed Manakin.” Wilson Bulletin 83:3–38.

*———(1963) “The Display of the Blue-backed Manakin, Chiroxiphia pareola, in Tobago, W.I.” Zoologica 48:167–76.

Antbirds get their name because they follow large swarms of army ants for food, often in flocks containing several different bird species. Both Bicolored and Ocellated Antbirds form monogamous pairs that are generally long-lasting. In addition, Ocellated Antbirds live in a complex extended family or “clan” structure, typically containing up to three generations of males and their mates. Females emigrate from these units to join other clans, while males often return to their extended family once they have found mates.

Behavioral Expression: Male homosexual pairs are a distinctive feature of Bicolored and Ocellated Antbird social life. Usually the pair-bond is initiated and strengthened (as in heterosexual pairs) when one male COURTSHIP-FEEDS the other, that is, ritually presents him with a “gift” of food (usually an insect or spider). In Ocellated Antbirds, males who court each other this way often adopt a characteristic pose (also used in heterosexual courtship)—ruffled throat feathers, stiff neck and upright posture, fluffed-out body feathers, with tail and legs spread. They also CAROL, producing a series of up to 15 whistled notes that decrease in pitch (sounding like chee chee chew chew). Unlike heterosexual mates, male partners typically reciprocate courtship feeding by passing the food gift back and forth between them. Homosexual courtship-feeding in Bicolored Antbirds is distinct from the heterosexual pattern in a number of other ways as well: either partner may initiate the activity in a male pair, and courtship-feeding is usually accompanied by CHIRPING—brief, musical cheup notes. In heterosexual pairs, only the male feeds the female, and the partners typically utter GROWLS during courtship-feeding (a rapid hissing or grunting noise composed of rough chauhh notes). Once paired, two males are constant companions, visiting ant swarms together and foraging side by side much as opposite-sex mated pairs do. Homosexual pair-bonds are sometimes long-lasting associations, persisting for many years. Partners may both be adults, or an older bird may pair with a younger one. In Ocellated Antbirds, father-son courtship-feedings also sometimes occur when a younger male remains within the clan structure.

Frequency: In Bicolored Antbirds, an estimated 2-3 percent of all pairs in some populations are composed of two males, and homosexual pairs may constitute up to 4-6 percent of the total number of pairs in any given year. The incidence of male pairs in Ocellated Antbirds is probably comparable.

Orientation: Approximately 5-14 percent of male Bicolored Antbirds may participate in a homosexual pairing or courtship at some point in their life. In both species, some males exhibit sequential bisexuality. In a few cases, for example, males have been mated to a female prior to their homosexual pairing (they may even have fathered young, and some are widowers), or they may go on to mate with a female when a homosexual pairing breaks up. Other males, however, show no signs of participating in heterosexual mating, and these birds may be involved exclusively in homosexual pairs, at least for a portion of their lives.

In both Bicolored and Ocellated Antbirds, significant numbers of birds are nonbreeding. As many as 45 percent of adult Bicolored males may not be heterosexually paired in any given year, and some males fail to acquire a mate for six or more years in a row. Younger males may delay their reproductive careers for up to a year after reaching sexual maturity—by remaining “at home” in their clans (Ocellateds) or wandering solitarily (Bicoloreds). In addition, male Antbirds have been known to live to a relatively old age—more than 11 years in Bicoloreds and Ocel-lateds. For a few individuals who have lost their female partners (either through death or divorce), this may be a postreproductive period in their lives. In addition to females leaving their mates for younger males, divorce and mate-switching also occasionally happen in adult Bicolored and newly paired Ocellated Antbirds. Often, a divorce is initiated by “extramarital” courtship between a mated female and an unpaired male. The extended families of Ocellated Antbirds also sometimes break up: heterosexual pairs wander off from the clan if they have not been able to breed successfully, or grandparents isolate themselves from their relatives. Heterosexual relations within a pair are not always smooth either: in Bicoloreds, for example, males are often distinctly hostile to their female mates. This is especially true early in their pair-bond, when he may aggressively “blast” her off her perch with hissing and snapping. Female Ocellated Antbirds have also been observed steadfastly refusing the courtship and copulatory advances of males. Finally, a number of incestuous activities have been documented in these species, including courtship and attempted copulation between Ocellated males and their mothers, and courtship of Bicolored daughters by their fathers.

*asterisked references discuss homosexuality/transgender

Willis, E.O. (1983) “Longevities of Some Panamanian Forest Birds, with Note of Low Survivorship in Old Spotted Antbirds (Hylophylax naevioides).” Journal of Field Ornithology54:413-14.

*———(1973) The Behavior of Ocellated Antbirds. Smithsonian Contributions to Zoology no. 144. Washington, D.C.: Smithsonian Institution Press.

*———(1972) The Behavior of Spotted Antbirds. Ornithological Monographs 10. Washington, D.C.: American Ornithologists’ Union.

*———(1967) The Behavior of Bicolored Antbirds. University of California Publications in Zoology 79. Berkeley: University of California Press.

Ocher-bellied Flycatchers have a complex social organization, with three distinct categories of males. About 42 percent of males are TERRITORIAL, defending “courts” in the foliage within which they perform courtship displays; sometimes groups of two to six territorial males display close to each other in a LEK formation. Another 10 percent of males are SATELLITES, who associate with territorial males but do not display; they often eventually inherit the territory themselves. Finally, 48 percent of males are FLOATERS, who travel widely and do not hold any territories themselves. The mating system of Ocher-bellies is polygamous or promiscuous. No male-female pair-bonds are formed; instead, males mate with as many females as they can, but the female raises the young on her own.

Behavioral Expression: Female Ocher-bellied Flycatchers are usually attracted to males displaying and singing on their territories, but sometimes another male approaches and is courted by the territorial male. The approaching male behaves much like a female, moving toward the center of the display court flicking his wings while the other male sings more intensely (making whistlelike notes), crouching and wing-flicking. The territorial male then trails the other male, following him closely and sometimes making soft ipp calls. The courtship sequence continues as in a heterosexual encounter with a series of three types of flight displays by the territorial male. The HOP DISPLAY involves the male bouncing excitedly back and forth between two perches uttering an eek call. In the FLUTTER FLIGHT, the displaying male traverses an arc between two perches with a special, slow wing-fluttering pattern, while in the HOVER FLIGHT, the male slowly rises in a hover above his perch or between two perches, often fairly close to the other male. The courtship sequence typically ends abruptly with the territorial male chasing the other male off while making chur calls.

Frequency: Approximately 17 percent of courtship sequences involve a male displaying to another male, and about 5 percent of male visits to territories result in courtship. Although no mountings or attempted copulations between males have been seen, heterosexual matings have rarely been witnessed either. At one study site, for example, only two male-female mountings were observed during more than 560 hours of observation over ten months.

Orientation: It is difficult to determine the relative proportion and “preference” of heterosexual versus homosexual behavior in Ocher-bellied Flycatchers. Some researchers believe that territorial males who court other males do not realize they are displaying to a bird of the same sex, in which case they would be exhibiting superficially heterosexual behavior toward (behaviorally) “transvestite” birds. For the males who approach territorial males, however, the situation is even less clear: many of these are probably floaters who presumably are aware that they are being courted by another male, i.e., they are ostensibly participating in homosexual activity. However, in at least one case the approaching male was a neighboring territorial male who also displayed to females on his own territory, i.e., his courtship interactions were actually bisexual.

As noted above, more than half of the male population consists of nonbreeders, since floaters and satellites rarely, if ever, mate heterosexually. Moreover, the absence of breeding activity in these males cannot be attributed to a shortage of available display sites, since more than three-quarters of suitable territories go unused (and nearly a quarter of these are especially prime pieces of “real estate”).

*asterisked references discuss homosexuality/transgender

Sherry, T. W. (1983) “Mionectes oleaginea.” In D. H. Janzen, ed., Costa Rican Natural History, pp. 586-87. Chicago: University of Chicago Press.

Skutch, A. E (1960) “Oleaginous pipromorpha.” In Life Histories of Central American Birds II, Pacific Coast Avifauna no. 34, pp. 561-70. Berkeley: Cooper Ornithological Society.

Snow, B. K., and D. W. Snow (1979) “The Ocher-bellied Flycatcher and the Evolution of Lek Behavior.” Condor 81:286-92.

Westcott, D. A. (1997) “Neighbors, Strangers, and Male-Male Aggression as a Determinant of Lek Size.” Behavioral Ecology and Sociobiology 40:235-42.

———(1993) “Habitat Characteristics of Lek Sites and Their Availability for the Ocher-bellied Flycatcher, Mionectes oleagineus.” Biotropica 25:444-51.

———(1992) “Inter- and Intra-Sexual Selection: The Role of Song in a Lek Mating System.” Animal Behavior 44:695-703.

*Westcott, D. A., and J. N. M. Smith (1994) “Behavior and Social Organization During the Breeding Season in Mionectes oleagineus, a Lekking Flycatcher.” Condor 96:672-83.

SWALLOWS, WARBLERS, FINCHES, AND OTHERS

Tree Swallows are extremely social birds: outside of the mating season, they gather in large flocks that may contain several hundred thousand individuals, while during the breeding season they form pairs and often nest in aggregations or colonies.

Behavioral Expression: Groups of male Tree Swallows sometimes pursue other males during the mating season in order to copulate with them. When the object of their attentions alights, the males hover in a “cloud” above him, constantly fluttering and making the distinctive tick-tick-tick call that is characteristic of males when they are mating with females. If one of them succeeds in mounting the male, a complete homosexual copulation ensues: the male on top holds on to the other male’s neck and back feathers with his bill, while the male being mounted lifts his tail so that genital contact can occur. As in heterosexual mating, multiple, repeated genital contacts may occur during a single copulation between two males, which can last for up to a minute (male-female mounts generally last about 30 seconds). The cluster of males may also engage in several consecutive episodes of homosexual mating: when the male who was mounted flies off, the group will continue pursuing him until he lands again, and the whole process is repeated.

Frequency: Homosexual copulations have been observed only occasionally in Tree Swallows. However, heterosexual nonmonogamous matings are also rarely seen in this species, yet they are known to be very common because of the high rate of offspring that result from them (see below). Most such copulations therefore probably occur in locations where (or at times when) they are not readily observed. Homosexual matings (which follow the pattern of nonmonogamous copulations) probably also occur more often than they are observed.

Orientation: Some males that participate in homosexual pursuits and copulations are probably bisexual: for example, one male who was mounted by other males was the father of six-day-old nestlings when he participated in homosexual activity. The males mounting him were not paired with female mates in the same nesting colony, however, and may have been nonbreeders (although they could also have been heterosexually paired birds visiting from another colony).

Heterosexual pairs of Tree Swallows sometimes copulate well before the female is fertile, and nonreproductive matings may also occur after the eggs are laid or even following hatching of chicks. Overall, each pair copulates about 50-70 times per clutch of eggs produced. At least 15 percent of matings also occur after the female’s fertile period, and more than 20 percent of mounts do not involve genital contact. In addition, a large number of heterosexual copulations that take place during incubation—as well as throughout the breeding season—are nonmonogamous matings between a female and a male other than her mate. Although many pairs are monogamous in this species (about half of all females are strictly faithful), promiscuous copulations are a prominent feature of Tree Swallow heterosexual interactions. Females often solicit such copulations (sometimes from several different males) and are also able to effectively terminate unwanted promiscuous matings. They do this by flying away, refusing to lift their tail for genital contact, or turning their head and snapping or “chattering” at the male. Nonmonogamous matings frequently result in offspring: in some populations, 50-90 percent of all nests contain young that are not genetically related to their mother’s mate, and these constitute 40-75 percent of all nestlings. In some families, all the offspring are fathered by other males. The opposite situation also sometimes occurs: youngsters may be related to the father but not his female partner. This may result from mate-switching (divorce and remating), or because females occasionally lay eggs in another female’s nests (5-9 percent of all nests are PARASITIZED this way).

In some populations, 3-8 percent of males form polygamous trios in which they bond and breed with two females simultaneously. If the two females share a nest, one may help care for the other’s nestlings if her own eggs do not hatch. Many populations also have large numbers of nonbreeding birds, sometimes called FLOATERS because they do not occupy their own territories and tend to travel widely. As many as a quarter of all reproductively mature females are floaters. In addition to helping raise unrelated birds of their own species, Tree Swallows sometimes “adopt” nests belonging to other birds such as purple martins (Progne subis) or bluebirds (Sialia spp.), raising the foster young in addition to their own. More than half of all Tree Swallow heterosexual pairs do not remain together for more than one breeding season. Single parenting also occasionally occurs in this species, for example if one parent is killed or dies during the breeding season. Frequently, however, the widowed parent re-pairs with another mate. If a single parent is laying or incubating eggs, its new mate often adopts the brood, but if a single parent already has nestlings from the previous mate, the new partner often kills them (usually by pecking) in order to begin breeding himself or herself. Infanticide also sometimes occurs when a female kills a paired female’s nestlings in order to try to precipitate a divorce and mate with her partner.

*asterisked references discuss homosexuality/transgender

Barber, C. A., R. J. Robertson, and P. T. Boag (1996) “The High Frequency of Extra-Pair Paternity in Tree Swallows Is Not an Artifact of Nestboxes.” Behavioral Ecology and Sociobiology 38:425-30.

Chek, A. A., and R. J. Robertson (1991) “Infanticide in Female Tree Swallows: A Role for Sexual Selection.” Condor 93:454-57.

Dunn, P. O., and R. J. Robertson (1992) “Geographic Variation in the Importance of Male Parental Care and Mating Systems in Tree Swallows.” Behavioral Ecology 3:291-99.

Dunn, P. O., and R. J. Robertson, D. Michaud-Freeman, and P. T. Boag (1994) “Extra-Pair Paternity in Tree Swallows: Why Do Females Mate with More than One Male?” Behavioral Ecology and Sociobiology 35:273-81.

Leffelaar, D., and R. J. Robertson (1985) “Nest Usurpation and Female Competition for Breeding Opportunities by Tree Swallows.” Wilson Bulletin 97:221-24

———(1984) “Do Male Tree Swallows Guard Their Mates?” Behavioral Ecology and Sociobiology 16:73-79.

Lifjeld, J. T., P. O. Dunn, R. J. Robertson, and P. T. Boag (1993) “Extra-Pair Paternity in Monogamous Tree Swallows.” Animal Behavior 45:213-29.

Lifjeld, J. T., and R. J. Robertson (1992) “Female Control of Extra-Pair Fertilization in Tree Swallows.” Behavioral Ecology and Sociobiology 31:89-96.

*Lombardo, M. P. (1996) Personal communication.

———(1988) “Evidence of Intraspecific Brood Parasitism in the Tree Swallow.” Wilson Bulletin 100:126–28.

———(1986) “Extrapair Copulations in the Tree Swallow.” Wilson Bulletin 98:150-52.

*Lombardo, M. P., R. M. Bosman, C. A. Faro, S. G. Houtteman, and T.S. Kluisza (1994) “Homosexual Copulations by Male Tree Swallows.” Wilson Bulletin 106:555-57.

Morrill, S. B., and R. J. Robertson (1990) “Occurrence of Extra-Pair Copulation in the Tree Swallow (Tachycineta bicolor).” Behavioral Ecology and Sociobiology 26:291-96.

Quinney, T. E. (1983) “Tree Swallows Cross a Polygyny Threshold.” Auk 100:750-54.

Rendell, W. B. (1992) “Peculiar Behavior of a Subadult Female Tree Swallow.” Wilson Bulletin 104:756-59.

Robertson, R. J. (1990) “Tactics and Counter-Tactics of Sexually Selected Infanticide in Tree Swallows.” In J. Blondel, A. Gosler, J.-D. Lebreton, and R. McCleery, eds., Population Biology of Passerine Birds: An Integrated Approach, pp. 381-90. Berlin: Springer-Verlag.

Robertson, R. J., B. J. Stutchbury, and R. R. Cohen (1992) “Tree Swallow (Tachycineta bicolor).” In A. Poole, P. Stettenheim, and F. Gill, eds., The Birds of North America: Life Histories for the 21st Century, no. 11. Philadelphia: Academy of Natural Sciences; Washington, D.C.: American Ornithologists’ Union.

Stutchbury, B. J., and R. J. Robertson (1987a) “Signaling Subordinate and Female Status: Two Hypotheses for the Adaptive Significance of Subadult Plumage in Female Tree Swallows.” Auk 104:717-23.

———(1987b) “Behavioral Tactics of Subadult Female Floaters in the Tree Swallow.” Behavioral Ecology and Sociobiology 20:413-19.

———(1987c) “Two Methods of Sexing Adult Tree Swallows Before They Begin Breeding.” Journal of Field Ornithology 58:236-42.

———(1985) “Floating Populations of Female Tree Swallows.” Auk 102:651-54.

Venier, L. A., P. O. Dunn, J. T. Lifjeld, and R. J. Robertson (1993) “Behavioral Patterns of Extra-Pair Copulation in Tree Swallows.” Animal Behavior 45:412-15.

Venier, L. A., and R. J. Robertson (1991) “Copulation Behavior of the Tree Swallow, Tachycineta bicolor: Paternity Assurance in the Presence of Sperm Competition.” Animal Behavior 42:939-48.

Cliff and Bank Swallows are highly gregarious and may flock by the hundreds or even thousands. They generally form mated pairs (although many alternative arrangements also occur, see below) and nest in colonies. Cliff Swallow colonies are the largest of any swallow in the world, often containing a thousand nests (and sometimes up to three times this number).

Behavioral Expression: Male Cliff and Bank Swallows often try to copulate with both males and females that are not their own mates. Unlike in Tree Swallows, these are usually forced copulations or “rapes,” since the bird being pursued—whether male or female—does not welcome the sexual advances of the male. Homosexual copulation attempts in Cliff Swallows take place on the ground at social gatherings of birds that are sunning themselves or gathering mud or grass for nests. Anywhere from a handful to several hundred individuals may be present at a time, although such groups usually contain 10-30 birds. At mud-gathering sessions, one male pounces on another male from above, landing on his back and often grabbing his head or neck feathers in his beak. At sunning sites, the male usually lands a few inches away from the other bird and makes threatening HEAD-FORWARD displays prior to jumping on his back. Once mounted, he spreads his tail and moves it sideways, trying to make cloacal (genital) contact, all the while vigorously flapping his wings; the other male usually strongly resists, and sometimes a fight ensues, before both birds fly off. The entire copulation attempt is usually quite brief, though it can last for up to 10 seconds (a relatively long duration for bird mountings). Forcible mountings of females follow this same pattern. When on the ground at mud-gathering sites, birds of both sexes typically flutter their wings above their backs to try to prevent males from mounting them.

Male Bank Swallows also pursue both females and males to try to copulate with them. Males first make many INVESTIGATORY CHASES of unfamiliar birds to determine if they are worth following. If they find a bird they are interested in—which may be another male—a full-fledged SEXUAL CHASE ensues, sometimes drawing several birds into the pursuit as well. Often the targeted bird is able to get away, but sometimes the chase ends with a forced copulation attempt. Homosexual mountings also occur when birds congregate on the ground, for instance to gather nest materials or dust themselves. At times, a veritable “orgy” develops as numerous males frantically try to mount birds of both sexes. Sometimes one or two males will even mount a third male who is already copulating with another bird.

Frequency: In Bank Swallows, 8 percent of sexual chases are homosexual, while 36-40 percent of investigatory chases involve males pursuing other males. Cliff Swallow rape attempts are extremely common, occurring every two to three minutes at some mud-gathering sites; one male may attempt to mount six to eight different birds in a five-to-ten-minute period. These mounts are probably fairly evenly distributed between males and females, although homosexual mounts may in fact occur more often. When presented with stuffed birds of both sexes in identical poses, male Cliff Swallows mounted other males nearly 65 percent of the time.

Orientation: Most, if not all, male Cliff and Bank Swallows that pursue copulations with other males also try to forcibly mount females, and to this extent they are bisexual. However, in Cliff Swallows only a few males appear to engage in such behavior with either males or females. Many of these are unpaired birds, although males who are already heterosexually paired (including fathers) also sometimes participate in promiscuous copulations.

Heterosexual social life in Cliff and Bank Swallows is replete with behaviors that deviate from the monogamous-pair/nuclear-family model. As discussed above, a large proportion of heterosexually mated Swallows seek copulations with birds other than their partner, and considerable evidence suggests that these mounting attempts are nonprocreative. Because of the resistance of the bird being mounted, the copulation is often not completed and sperm is rarely transferred. In addition, such attempts may also occur outside the breeding season when there is no possibility of fertilization. Genetic studies have shown that probably only 2-6 percent of Cliff Swallow nests have young that might result from nonmonogamous sexual activity. However, nearly a quarter of all nestlings, in more than half of all nests, are raised by birds other than their biological mother and/or father. This is because Cliff Swallows participate in an extraordinary array of activities that serve to exchange eggs and nestlings between families. For example, as many as 43 percent of all nests contain an egg laid by an outside female—this bird usually has her own nest, but she also PARASITIZES or adds eggs to other nests (and often has eggs added to her own as well). In some cases, this female may even return to the foreign nest to incubate the entire clutch (even though only one egg is hers), but she does not help raise the nestlings once they hatch. Often the intruding female’s mate will destroy or toss out eggs in the host nest to make room for their own (up to 20 percent of all nests may suffer egg destruction). In other cases, males appear to destroy eggs in other nests so as to keep the laying female sexually receptive, thereby increasing the opportunities for heterosexual nonmonogamous matings. Birds also occasionally physically carry eggs from their own nest to another—about 6 percent of all nests contain eggs transferred this way. Finally, in a few cases Swallows have even been seen transferring actual baby birds between nests. Infanticide may also occur when birds attack and toss nestlings out of neighbors’ nests. In both species, young birds gather into large CRÈCHES or “day-care centers”—sometimes containing up to a thousand youngsters—which give them protection while their parents are away searching for food.

Divorce and single parenting also occur in Bank Swallows: females sometimes desert their mates to start a new family with another male, forcing their first mate to raise the nestlings on his own. In addition to the rape attempts described above, there is considerable aggression between the sexes as well. Ironically, male Bank Swallows often become violent toward their own female partners when trying to protect them from the advances of other males. Sometimes they knock their mate to the ground, fighting her directly, or try to force her back into their burrow. Nonreproductive sexual behaviors are also prevalent in these two species. Besides copulations outside the breeding season and group sexual activity (mentioned above), members of a Cliff Swallow pair often copulate at a rate far in excess of that needed simply to fertilize their eggs. In addition, males of both species have occasionally been seen trying to mate with dead birds, as well as with other species such as barn swallows (Hirundo rustica) and Tree Swallows.

*asterisked references discuss homosexuality/transgender

*Barlow, J. C., E. E. Klaas, and J. L. Lenz (1963) “Sunning of Bank Swallows and Cliff Swallows.” Condor 65:438-48.

Beecher, M. D., and 1. M. Beecher (1979) “Sociobiology of Bank Swallows: Reproductive Strategy of the Male.” Science 205:1282-85.

Beecher, M. D., I. M. Beecher, and S. Lumpkin (1981) “Parent-Offspring Recognition in Bank Swallows (Riparia riparia): I. Natural History.” Animal Behavior 29:86-94.

Brewster, W. (1898) “Revival of the Sexual Passion in Birds in Autumn.” Auk 15:194-95.

*Brown, C. R., and M.B. Brown (1996) Coloniality in the Cliff Swallow: The Effect of Group Size on Social Behavior. Chicago: University of Chicago Press.

*———(1995) “Cliff Swallow (Hirundo pyrrhonota).” In A. Poole and F. Gill, eds., The Birds of North America: Life Histories for the 21st Century, no. 149. Philadelphia: Academy of Natural Sciences; Washington, D.C.: American Ornithologists’ Union.

———(1989) “Behavioral Dynamics of Intraspecific Brood Parasitism in Colonial Cliff Swallows.” Animal Behavior 37:777-96.

———(1988a) “A New Form of Reproductive Parasitism in Cliff Swallows.” Nature 331:66-68.

———(1988b) “The Costs and Benefits of Egg Destruction by Conspecifics in Colonial Cliff Swallows.” Auk 105:737-48.

———(1988c) “Genetic Evidence of Multiple Parentage in Broods of Cliff Swallows.” Behavioral Ecology and Sociobiology 23:379-87.

Butler, R. W. (1982) “Wing-fluttering by Mud-gathering Cliff Swallows: Avoidance of ‘Rape’ Attempts?” Auk 99:758-61.

*Carr, D. (1968) “Behavior of Sand Martins on the Ground.” British Birds 61:416-17.

Cowley, E. (1983) “Multi-Brooding and Mate Infidelity in the Sand Martin.” Bird Study 30:1-7.

*Emlen, J. T., Jr. (1954) “Territory, Nest Building, and Pair Formation in Cliff Swallows.” Auk 71:16-35.

———(1952) “Social Behavior in Nesting Cliff Swallows.” Condor 54:177-99.

Hoogland, J. L., and P. W. Sherman (1976) “Advantages and Disadvantages of Bank Swallow (Riparia riparia) Coloniality.” Ecological Monographs 46:33-58.

*Jones, G. (1986) “Sexual Chases in Sand Martins (Riparia riparia): Cues for Males to Increase Their Reproductive Success.” Behavioral Ecology and Sociobiology 19:179-85.

*Petersen, A. J. (1955) “The Breeding Cycle in the Bank Swallow.” Wilson Bulletin 67:235-86.

Thom, A. S. (1947) “Display of Sand-Martin.” British Birds 40:20-21.

During the breeding season, male Hooded Warblers establish and defend territories, attracting mates with whom they usually form pair-bonds. Outside of the mating season, birds migrate south to their winter homes, where the two sexes live largely separate from each other.

Behavioral Expression: Male Hooded Warblers occasionally form homosexual pairs and become joint parents. Same-sex pair-bonds develop early in the mating season when one male is attracted to another male’s territory by his singing. In some cases, this is a male he has previously “prospected” on a visit to his territory during the prior mating season. Once a pair-bond is established, the males focus their attentions on parenting duties. Homosexual couples acquire nests and eggs in a variety of ways. Some pairs may build their own nests: although male Hooded Warblers in heterosexual pairs rarely build nests, at least one bird in a homosexual pair was observed carrying grass fibers to a nest and shaping the cup by repeatedly sitting in the nest and shifting his position. It is not known, however, whether he had built the nest or was simply adding material to a nest built by another pair. As for eggs, some pairs incubate eggs laid by another species of bird, the Brown-headed Cowbird. This species is known as a PARASITE because it always lays its eggs in the nests of other birds, “forcing” them to raise its young. Hooded Warblers are particularly susceptible to parasitism by Cowbirds: in some populations, three-quarters of all nests are parasitized, and Cowbirds appear to prefer Hooded Warbler nests over those of other species. Cowbirds occasionally lay eggs in completely empty nests, so some homosexual pairs of Hooded Warblers may build their own nest and end up tending only Cowbird eggs. Usually, though, a Cowbird adds its egg(s) to a nest that already has eggs (often removing part of the original clutch). Sometimes a Hooded Warbler mother abandons her nest once it has been disturbed this way, and some homosexual pairs may “adopt” such abandoned nests, or else the father of such a nest may re-pair with a male following the mother’s abandonment. At least two male pairs have been observed tending nests that were parasitized, since they each contained both Cowbird and Hooded Warbler chicks. Other male couples probably adopt nests that have been abandoned after attacks by predators. Bluejays and squirrels often prey on Hooded Warbler nestlings, and usually their mother will abandon the entire nest even if only one youngster has been taken. Finally, some homosexual pairs may tend eggs that have been directly laid in their nest by a female Hooded Warbler. In many bird species, females lay eggs in nests belonging to other birds of the same species (this is another form of parasitism); although this rarely occurs in Hooded Warblers, it is a possible source of eggs for homosexual pairs.

Once they have acquired a nestful of eggs, male couples typically divide up the parenting duties: one attends to nest repair, incubation of the eggs, and brooding of the nestlings, while the other feeds his mate and defends the territory. Both birds feed the nestlings insects such as crane flies. Although this division of labor is similar to that in heterosexual pairs—females typically build nests and incubate, males defend territories, and both feed nestlings—there are crucial differences. In homosexual pairs, incubating males are often fed by their mate, which occurs only rarely in heterosexual pairs. In addition, one male who engaged in typically “female” parental duties was later observed performing territorial singing (albeit with a song pattern that differed from that of most other males). Nests belonging to homosexual pairs are often lost entirely to predators, but up to 50 percent or more of all heterosexual nests are lost in the same way. The male couples that have been followed over a longer time do not appear to re-pair with the same mate in subsequent breeding seasons; their divorces may be related to the loss of nests to predators. Heterosexual divorce is also common in Hooded Warblers, with as many as half of all male-female pairs failing to remain together, perhaps also due in large part to loss of nests. It is possible as well that divorce is simply a general feature of pair-bonding in this species (heterosexual or homosexual) independent of nest losses, or that the particular pairs being studied happened to end in divorce without this being indicative of a larger pattern.

Some female Hooded Warblers are transvestite, having the same black hood that males do. In fact there is a continuum of transgendered physical appearance in females: some have no black feathers on their head at all, some have an intermediate amount with a black “bib” around the throat, while others are almost indistinguishable from males. In addition, a few females can sing (typically only males in this species are able to sing). Transgendered females usually mate with males and raise young just like nontransgendered females.

Frequency: The overall incidence of homosexual pairs in Hooded Warblers is not known, since no widespread, systematic study has yet been conducted to determine their prevalence. However, in one population observed over three years, 4 percent of the pair-bonds (3 of 80) were between males. Although overt sexual behavior has not yet been observed between such pair-mates, heterosexual copulations (both within-pair and nonmongamous) are rarely seen in this species either; it is possible, therefore, that homosexual copulations do take place. Among females, plumage transvestism is a regular occurrence, as about 59 percent of females have some degree of malelike black feathers on their head: 40 percent have only a slight amount, 17 percent an intermediate amount, and 2 percent have a nearly complete black hood.

Orientation: Some male Hooded Warblers appear to be exclusively homosexual, pairing only with males; if they divorce a male partner, they re-pair with another male in subsequent breeding seasons. These males often perform parenting duties typically associated with females in heterosexual pairs. Other males, however, are bisexual, alternating between homosexual pairings and heterosexual ones in different breeding seasons.

As mentioned above, heterosexual divorce is common in Hooded Warblers, as are a number of other variations on the nuclear family and monogamous pair-bond. About 4 percent of males form trios, mating with two females who both nest simultaneously on the male’s territory; 6 percent of males are nonbreeders, and some females remain single as well. Among paired birds, promiscuous copulations also occur very frequently: 30—50 percent of all females copulate with males other than their mates (usually neighboring males), and more than a third of all nestlings in some populations are fathered by a bird other than their mother’s mate. In addition, males sometimes adopt young birds from neighboring families whose own parents have finished caring for them; adoptive fathers typically feed these youngsters along with their own nestlings. The adopted birds are usually not genetically related to their foster fathers, i.e., they are not the result of promiscuous matings by the bird who adopts them. Single parenting is also a regular occurrence in Hooded Warblers: once their young can fly, parents usually separate and each takes care of half the brood (unless the female begins a second family, in which case the male will assume responsibility for all of the youngsters). In fact, single parenting is generally more extensive and longer-lasting than male-female coparenting in this species. Nestlings receive biparental care for only eight or nine days, while single parenting can last for three to six weeks and involves feeding rates that are three to five times higher than that of coparents. As a result of separation of mated pairs, males and females are together for only about one month out of the entire year. During the winter, the two sexes occupy largely segregated habitats, with males preferring forests and females scrub areas.

*asterisked references discuss homosexuality/transgender

Evans Ogden, L. J., and B. J. Stutchbury (1997) “Fledgling Care and Male Parental Effort in the Hooded Warbler (Wilsonia citrina).” Canadian Journal of Zoology 75:576—81.

———(1994) “Hooded Warbler (Wilsonia citrina):” In A. Poole and F. Gill, eds., The Birds of North America: Life Histories for the 21st Century, no. 110. Philadelphia: Academy of Natural Sciences; Washington, D.C.: American Ornithologists’ Union.

Godard, R. (1993) “Tit for Tat Among Neighboring Hooded Warblers.” Behavioral Ecology and Sociobiology 33:45—50.

———(1986) “Long-Term Memory of Individual Neighbors in a Migratory Songbird.” Nature 350:228—29.

*Lynch, J. F., E. S. Morton, and M. E. Van der Voort (1985) “Habitat Segregation Between the Sexes of Wintering Hooded Warblers (Wilsonia citrina).” Auk 102:714—21.

*Morton, E. S. (1989) “Female Hooded Warbler Plumage Does Not Become More Male-Like With Age.” Wilson Bulletin 101:460—62.

*Niven, D. K. (1997) Personal communication.

*———(1993) “Male-Male Nesting Behavior in Hooded Warblers.” Wilson Bulletin 105:190—93.

Stutchbury, B. J. M. (1998) “Extra-Pair Mating Effort of Male Hooded Warblers, Wilsonia citrina.” Animal Behavior 55:553—61.

*———(1994) “Competition for Winter Territories in a Neotropical Migrant: The Role of Age, Sex, and Color.” Auk 111:63—69.

Stutchbury, B. J., and L. J. Evans Ogden (1996) “Fledgling Adoption in Hooded Warblers (Wilsonia citrina): Does Extrapair Paternity Play a Role?” Auk 113:218—20.

*Stutchbury, B. J., and J. S. Howlett (1995) “Does Male-Like Coloration of Female Hooded Warblers Increase Nest Predation?” Condor 97:559—64.

Stutchbury, B. J., J. M. Rhymer, and E. S. Morton (1994) “Extrapair Paternity in Hooded Warblers.” Behavioral Ecology 5:384—92.

Chaffinches and Scottish Crossbills commonly associate in flocks; the mating system involves (usually monogamous) pair-bonding.

Behavioral Expression: Female Chaffinches sometimes form homosexual pair-bonds with each other. In this species, usually only males sing; however, in same-sex pairs, one female partner typically sings much in the manner of a male, throwing back her head while perched conspicuously in the trees (this is probably how she attracts her female mate). Her song resembles that of males in duration, loudness, and structure, consisting of a long stream of rapidly trilled notes of descending pitch, finished off with a staccato end phrase or “flourish.” It differs from male song, however, in having not quite as ringing a tone. Like male Chaffinches, she may even COUNTERSING in response to a neighboring male’s song, the two birds “replying” to each other with alternating or syncopated song phrases. Females in same-sex pairs may also try to sing together, although one partner may only be able to produce an incomplete version of the song. The two females behave like other mated couples, and may even engage in courtship pursuits known as SEXUAL CHASES. In this activity—which is a demonstration of sexual interest—one female zigzags after her partner using a special form of flying known as MOTH FLIGHT (rapid, shallow wingbeats without the pauses or undulating quality typical of regular flight). Occasionally, juvenile males pursue other males in such sexual chases.

Homosexual couples also occur in Scottish Crossbills—but among males. A male attracts potential mates by singing high in a treetop, advertising his presence with a loud stream of notes transcribed as chip-chip-chip-gee-gee-gee chip-chip-chip. Most singing males respond aggressively to other males who enter their territory, but occasionally the displaying male does not chase away another male that is attracted to him. The two males may then pair up and associate in much the same way that heterosexual couples do, except that copulation has not been observed between male partners. They synchronize their movements, traveling together between forest clumps, sometimes one leading the other. Occasionally, two neighboring males who are each heterosexually mated become companions. The two forage together and jointly defend clumps of pine trees (their principal food source) while still maintaining their opposite-sex bonds. The two males may even visit their female mates together, attending first to one and then the other, with one male feeding his female partner while his male companion waits for him.

Frequency: In both of these species, homosexual pairs are probably only an occasional occurrence. Although no statistics concerning the incidence of same-sex pairing are available, in Chaffinches about 1 in 150 nests contains a SUPERNORMAL CLUTCH of 7–8 eggs. In many species such larger-than-average clutches are laid by female pairs, and this may also be true in Chaffinches (although their specific association with same-sex pairing has not yet been demonstrated).

Orientation: Individual Chaffinches or Scottish Crossbills who form same-sex associations have not been tracked throughout their entire lives to determine if they only pair with members of the same sex. However, since heterosexual pairs in these species are usually lifelong, it is not unlikely that homosexual pairs would be as well. In addition, some Scottish Crossbill males are bisexual, forming bonds with both males and females simultaneously.

A variety of nonprocreative heterosexual behaviors are found in Chaffinches and Scottish Crossbills. Chaffinch couples sometimes copulate during incubation (i.e., after fertilization has occurred), and only 40–50 percent of all matings during the fertilizable period involve full genital contact. Some pairs may attempt to mate more than 200 times for each clutch of eggs they produce, as often as 4 times an hour. Mounts are often not completed for a variety of reasons: the male may slip off the female’s back or mount in a reversed head-to-tail position, or (more commonly) either partner may flee from the other out of fear or because of provocation from its mate. In fact, heterosexual courtship and mating in this species often entails a considerable amount of aggressive behavior between the sexes. Many birds do not participate in breeding at all: there are surplus flocks of single birds in many populations (males in Scottish Crossbills, both sexes in Chaffinches), as well as nonbreeding pairs in Scottish Crossbills. Interestingly, outside of the breeding season sexual segregation is also the rule. Males and female tend to migrate separately (wintering flocks are often same-sex), and females generally travel farther than males, often resulting in local populations with more males than females. In fact, this phenomenon has lent the Chaffinch its scientific name: coelebs means “bachelor” in Latin.

Scottish Crossbills frequently engage in “symbolic” matings early in the breeding season, in which the male mounts the female but no genital contact occurs. Sometimes these mounts are promiscuous: several males other than the female’s mate may participate. Nonmonogamous matings are also fairly common in Chaffinches, often between neighboring birds. About 8 percent of all mating activity involves nonmates, and 17 percent of all offspring (in a quarter of all broods) result from such copulations. Occasionally, a pair will separate or “divorce” during the breeding season, after which the single female may copulate with several already paired males. Eventually, a polygamous trio may develop if one of these males forms a pair-bond with her in addition to his own mate. Some Scottish Crossbills are also polygamous, forming trios of one male with two females. In this species, parents (in monogamous pairs) regularly become single parents: they separate when their young are able to fly, dividing the young between them and raising them on their own. Because the mother and father often travel to widely separated feeding grounds, youngsters belonging to the same family may be raised in very different environments. Occasionally, unrelated birds—both males and females—help feed and “foster-parent” the young birds after their biological parents have separated.

*asterisked references discuss homosexuality/transgender

Adkisson, C. S. (1996) “Red Crossbill (Loxia curvirostra).” In A. Poole, P. Stettenheim, and F. Gill, eds., The Birds of North America: Life Histories for the 21st Century, no. 256. Philadelphia: Academy of Natural Sciences; Washington, D.C.: American Ornithologists’ Union.

Halliday, H. (1948) “Song of Female Chaffinch.” British Birds 41:343-44.

Hanski, I. K. (1994) “Timing of Copulations and Mate Guarding in the Chaffinch Fringilla coelebs.” Ornis Fennica 71:17–25.

Kling, J. W., and J. Stevenson-Hinde (1977) “Development of Song and Reinforcing Effects of Song in Female Chaffinches.” Animal Behavior 25:215–20.

Knox, A. G. (1990) “The Sympatric Breeding of Common and Scottish Crossbills Loxia curvirostra and L. scotica and the Evolution of Crossbills.” Ibis 132:459—66.

*Marjakangas, A. (1981) “A Singing Chaffinch Fringilla coelebs in Female Plumage Paired with Another Female-Plumaged Chaffinch.” Ornis Fennica 58:90–91.

*Marler, P. (1956) Behavior of the Chaffinch Fringilla coelebs. Behavior Supplement V. Leiden: E. J. Brill.

———(1955) “Studies of Fighting in Chaffinches. 2. The Effect on Dominance Relations of Disguising Females as Males.” British Journal of Animal Behavior 3:137—46.

*Nethersole-Thompson, D. (1975) Pine Crossbills: A Scottish Contribution. Berkhamsted: T. and A. D. Poyser.

Sheldon, B. C. (1994) “Sperm Competition in the Chaffinch: The Role of the Female.” Animal Behavior 47:163–73.

Sheldon, B. C., and T. Burke (1994) “Copulation Behavior and Paternity in the Chaffinch.” Behavioral Ecology and Sociobiology 34:149–56.

Svensson, B. V. (1978) “Clutch Dimensions and Aspects of the Breeding Strategy of the Chaffinch Fringilla coelebs in Northern Europe: A Study Based on Egg Collections.” Ornis Scandinavica 9:66—83.

Voous, K. H. (1978) “The Scottish Crossbill Loxia scotica.” British Birds 71:3–10.

Red-backed Shrikes generally establish monogamous pair-bonds during the mating season and occupy partially overlapping territories. Outside of the breeding season, the birds are more solitary, and males and females typically occupy segregated habitats (males in more open bush country, females in more dense woodland). Blue Tits and Eastern Bluebirds are also territorial and form pair-bonds, but may associate in flocks outside of the breeding season.

Behavioral Expression: In Red-backed Shrikes and Blue Tits, two females sometimes pair with each other, build a nest, and lay eggs. Both partners in Red-backed Shrike homosexual pairs take turns incubating the eggs (in heterosexual pairs, only the female incubates). Sometimes they even sit on the nest together, side by side or one partially covering the other. Both females also lay eggs: as a result, their nests have SUPERNORMAL CLUTCHES of 9–12 eggs, twice the number in most nests belonging to heterosexual pairs. If their nest is robbed by predators, the pair will dutifully build a second one (often in a much higher location, to make it inaccessible to most ground predators) and begin laying eggs again (as do male-female pairs when they lose a nest). However, all of the eggs they lay are typically infertile since neither female has mated with a male, and the pair usually abandons the nest after the eggs have failed to hatch. Blue Tit female pairs are unlike most homosexual pairs in birds because only one female lays eggs. As a result, nests belonging to such pairs contain not supernormal clutches, but exceptionally small clutches of 3 or so eggs (nests of male-female pairs typically contain about 11 eggs). Both females incubate the eggs simultaneously, sitting together on the nest facing in the same direction. As in Red-backed Shrike homosexual pairs, the eggs are usually infertile and the pair eventually abandons the nest.

In Eastern Bluebirds, two males sometimes associate with one another in what appears to be a homosexual pair-bond: they travel exclusively in each other’s company (perhaps even spending the winter together), jointly inspect nest sites during the early spring, and court one another. The latter activity involves COURTSHIP-FEEDING—a behavior also seen in heterosexual pairs—in which one male offers a symbolic food gift, such as a cutworm, to the other male, often preceded by a distinctive call. Paired males might be related to each other (father-son or brothers). Occasionally, a female who has lost her heterosexual mate is joined by another female, who helps coparent her offspring. The two birds take turns feeding the youngsters and may also be assisted by one or more of their young from a previous brood.

Frequency: Same-sex pairs probably occur only sporadically in these three species: in Red-backed Shrikes, for example, female couples account for perhaps no more than 1 percent of all pairs.

Orientation: Female Red-backed Shrikes and Blue Tits are probably exclusively homosexual, at least for the time that they remain paired with their female partner, since they invariably lay eggs that are infertile (indicating no mating with males). Whether such birds ever subsequently form or have previously formed heterosexual pair-bonds is not known.

Approximately 17 percent of all sexual activity in opposite-sex pairs of Blue Tits occurs outside the female’s fertile period. Male Eastern Bluebirds also sometimes try to copulate when females are nonfertile, such as during incubation or after the breeding season is over. Other nonprocreative matings involve occasional interspecies encounters: juvenile Eastern Bluebirds have been observed being mounted by great crested flycatchers (Myiarchus crinitus). Courtship and mounting between pair-bonded Eastern Bluebirds sometimes involve considerable aggression, with males attacking their partner and violently pecking her head or knocking her over with their feet. Heterosexual copulations are also occasionally interrupted by neighboring birds that attack the mating pair. Within-pair copulation rates are quite high in Red-backed Shrikes, roughly three times a day during the female’s fertile period. In addition, nonmonogamous matings are common in these species: approximately 10 percent of Blue Tit copulations are promiscuous, involving birds that are not paired to each other. About a quarter of Bluebird nests and a third to nearly a half of all Blue Tit broods contain youngsters fathered by an outside bird. Promiscuous copulations also occasionally occur in Red-backed Shrikes, including forced matings or rapes in which males attack and mount females or violently push them off their perches. About 5 percent of Red-backed Shrike nestlings are fathered by a bird other than their mother’s mate, compared to 8–35 percent in Eastern Bluebirds, and 11–14 percent in Blue Tits.

Several other alternative parenting arrangements occur in these species. Red-backed Shrike youngsters sometimes move to adjacent territories where they are adopted by other families, and a few nonbreeding birds of both sexes help feed chicks belonging to other pairs (sometimes even assuming full responsibility for them later on). “Helper” males such as these may even replace the biological father as a model for song-learning by the youngsters. In addition, late-breeding Red-backed Shrikes sometimes become single parents when their mate deserts them; occasionally two such birds and their offspring join together to form a “blended family.” At least 15 percent of Eastern Bluebird mothers in some populations raise unrelated youngsters when outside females lay eggs in their nest. The divorce rate for Blue Tits varies considerably, from 8—85 percent (depending on the population); in addition, about a third of females and up to 20 percent of all males in some areas form polygamous trios (or occasionally quartets). Other more complex family arrangements also occur: one female Blue Tit was part of a polygamous trio with another female and a male; she also copulated promiscuously with a second male, eventually forming a new polygamous bond with both him and yet a third male, all of whom helped care for the young! Overall, however, more than 85 percent of Blue Tits never successfully breed, and about a third of all parents never have grandchildren. Red-backed Shrike parents occasionally cannibalize their own young or eggs.

Some male Pied Flycatchers (Ficedula hypoleuca), especially younger ones, are transvestite, having the same brownish plumage that females do; these birds are sometimes courted by other males.

*asterisked references discuss homosexuality/transgender

Alsop, F. J., III (1971) “Great Crested Flycatcher Observed Copulating with an Immature Eastern Bluebird.” Wilson Bulletin 83:312.

*Ashby, E. (1958) “Incidents of Bird Life [report on Red-backed Shrikes].” The Countryman: A Quarterly Review and Miscellany of Rural Life and Progress 55:272.

Birkhead, T. R., and A. P. Møller (1992) Sperm Competition in Birds: Evolutionary Causes and Consequences. London: Academic Press.

*Blakey, J. K. (1996) “Nest-Sharing by Female Blue Tits.” British Birds 89:279-80.

*Cramp, S., and C. M. Perrins, eds. (1993) “Red-backed Shrike (Lanius collurio).” In Handbook of the Birds of Europe, the Middle East, and North Africa, vol. 7, pp. 456—78. Oxford: Oxford University Press.

Dhondt, A. A. (1989) “Blue Tit.” In I. Newton, ed., Lifetime Reproduction in Birds, pp. 15—33. London: Academic Press.

———(1987) “Reproduction and Survival of Polygynous and Monogamous Blue Tit Parus caeruleus.” Ibis 129:327—34.

Dhondt, A. A., and F. Adriaensen (1994) “Causes and Effects of Divorce in the Blue Tit Parus caeruleus.” Journal of Animal Ecology 63:979—987.

Fornasari, L., L. Bottoni, N. Sacchi, and R. Massa (1994) “Home-Range Overlapping and Socio-Sexual Relationships in the Red-backed Shrike Lanius collurio.” Ethology, Ecology, and Evolution 6:169-177.

Gowaty, P. A., and W. C. Bridges (1991) “Behavioral, Demographic, and Environmental Correlates of Extrapair Fertilizations in Eastern Bluebirds, Sialia sialis.” Behavioral Ecology 2:339-50.

Gowaty, P. A., and A. A. Karlin (1984) “Multiple Maternity and Paternity in Single Broods of Apparently Monogamous Eastern Bluebirds (Sialia sialis).” Behavioral Ecology and Sociobiology 15:91—95.

Hartshorne, J. M. (1962) “Behavior of the Eastern Bluebird at the Nest.” Living Bird 1:131—49.

Herremans, M. (1997) “Habitat Segregation of Male and Female Red-backed Shrikes Lanius collurio and Lesser Gray Shrikes Lanius minor in the Kalahari Basin, Botswana.” Journal of Avian Biology 28:240—48.

Jakober, H., and W. Stauber (1994) “Kopulationen und Partnerbewachung beim Neuntöter Lanius collurio [Copulation and Mate-Guarding in the Red-backed Shrike].” Journal für Ornithologie 135:535—47.

———(1983) “Zur Phänologie einer Population des Neuntöters (Lanius collurio) [On the Phenology of a Population of the Red-backed Shrike].” Journal für Ornithologie 124:29—46.

Kempenaers, B. (1994) “Polygyny in the Blue Tit: Unbalanced Sex Ratio and Female Aggression Restrict Mate Choice.” Animal Behavior 47:943—57.

———(1993) “A Case of Polyandry in the Blue Tit: Female Extra-Pair Behavior Results in Extra Male Help.” Ornis Scandinavica 24:246—49.

Kempenaers, B., G. R. Verheyen, and A. A. Dhondt (1997) “Extrapair Paternity in the Blue Tit (Parus caeruleus): Female Choice, Male Characteristics, and Offspring Quality.” Behavioral Ecology 8:481-92.

———(1995) “Mate Guarding and Copulation Behavior in Monogamous and Polygynous Blue Tits: Do Males Follow a Best-of-a-Bad-Job Strategy?” Behavioral Ecology and Sociobiology 36:33—42.

Krieg, D. C. (1971) The Behavioral Patterns of the Eastern Bluebird (Sialia sialis). New York State Museum and Science Service Bulletin no. 415. Albany: University of the State of New York.

Massa, R., L. Bottoni, L. Fornasari, and N. Sacchi (1995) “Studies on the Socio-Sexual and Territorial System of the Red-backed Shrike.” Proceedings of the Western Foundation of Vertebrate Zoology 6:172-75.

Meek, S. B., R. J. Robertson, and P. T. Boag (1994) “Extrapair Paternity and Intraspecific Brood Parasitism in Eastern Bluebirds Revealed by DNA Fingerprinting.” Auk 111:739—44.

*Owen, J. H. (1946) “The Eggs of the Red-backed Shrike.” Oologists’ Record 20:38-43.

*Pinkowski, B.C. (1977) “‘Courtship Feeding’ Attempt Between Two Male Eastern Bluebirds.” Jack-Pine Warbler 55:45—46.

*Pounds, H. E. (1972) “Two Red-backed Shrikes Laying in One Nest.” British Birds 65:357—58.

*Sætre, G.-P., and T. Slagsvold (1993) “Evidence for Sex Recognition from Plumage Color by the Pied Flycatcher, Ficedula hypoleuca.” Animal Behavior 44:293—99.

*Slagsvold, T., and G.-P. Sætre (1991) “Evolution of Plumage Color in Male Pied Flycatchers (Ficedula hypoleuca): Evidence for Female Mimicry.” Evolution 45:910—17.

Stanback, M. T., and W. D. Koenig (1992) “Cannibalism in Birds.” In M.A. Elgar and B. J. Crespi, eds., Cannibalism: Ecology and Evolution Among Diverse Taxa, pp. 277-98. Oxford: Oxford University Press.

*Zeleny, L. (1976) The Bluebird: How You Can Help Its Fight for Survival. Bloomington: Indiana University Press.

SPARROWS, BLACKBIRDS, AND CROWS

Weaverbirds are named for the intricate—and often colossal—nests they weave. Sociable Weavers build giant condominium-like structures containing many nest chambers; each chamber may house up to 5 birds, while the entire colony can contain as many as 500 birds. Colonies of Gray-capped Social Weavers consist of family groups that each build several hanging nests (one is used as an actual nesting chamber, the others for sleeping). Several groups occupy the same tree, each situated in its own cluster. In both Gray-caps and Sociable Weavers, breeding birds form pair-bonds, and “helper” birds may assist them in their parenting duties. Adult male Bishop Birds establish territories during the breeding season on which they weave elaborate nests and court potential mates. The breeding system of Bishop Birds is polygynous: males mate with numerous females, each of whom lays eggs in one of the nests on his territory, but the male himself does not participate in any parental duties. Outside of the breeding season, Bishop Birds typically socialize in large, often mixed-species flocks.

Behavioral Expression: Male Gray-capped Social Weavers and Sociable Weavers sometimes participate in homosexual copulations. In Gray-caps, birds who participate in same-sex mounting are usually heterosexually paired males, often high-ranking individuals living in the same colony (tree). One male may fly from his home group in the tree to another male’s residence, inviting him to mate by holding his body horizontal, raising his head and tail upward, and drooping and vibrating his wings. The other male then mounts him and proceeds to engage in a complete copulation sequence, probably including cloacal (genital) contact. Mounting between males occurs in Sociable Weavers as well, and about 9 percent of such mounts are also full copulations in which the mounted male crouches, quivers his wings, and moves his tail to the side as the mounting male lowers his tail (probably to achieve genital contact). Usually higher-ranking males mount lower-ranking ones, but all males both mount and are mounted by other males (to varying degrees). In addition, some males appear to form “companionships” with each other. Although males do not generally permit other males to roost with them in their nesting chambers, occasionally two males regularly associate with one another and sleep together in the same nest. This can occur even if one of the males is already paired to a female, in which case all three birds occupy the nest together. The two males may remain together for years, even cooperating in attacking other birds together. Some male “companions” participate in mountings and copulations with each other, but in other cases males do not seem to preferentially engage in sexual behavior with their companion.

On their nesting territories, male Red Bishop Birds court both females and males, the latter usually being younger males who have brown plumage (as do females). Courtship consists of two components: a flying display and a perched display. When a young male appears near his territory, an adult male approaches in a distinctive BUMBLE-FLIGHT, in which he fluffs up all of his plumage and flies with slow wingbeats, resembling a bumble-bee. The bird’s bright red back or epaulet feathers are prominently displayed, and the bumble-flying may be accompanied by singing or a distinctive noise made by his flapping wings. Sometimes males bumble-fly toward another adult male rather than a younger male. After the display flight, the adult male lands near the other male and begins the SWIVEL DISPLAYS: he hops and twists around his perch, approaching the object of his attentions with ruffled plumage and a rattling call—a continuous stream of notes that sounds like zik-zik-zik. No homosexual copulations have been observed in this species in the wild, but heterosexual matings are not commonly seen either. In captivity Orange Bishop Birds—both adults and younger males—sometimes do try to mount younger males (including males of the closely related Golden Bishop Bird, Euplectes afer). In a homosexual encounter, one male approaches the other while pumping his body up and down and ruffling his feathers, followed by an attempt to copulate with the other male (who usually rejects his advances).

Frequency: In Sociable Weavers studied in captivity, as much as three-quarters of all mounting activity is between males, and three out of five full copulations are homosexual. The occurrence of same-sex mounting in wild birds of this species is not known, but its prevalence is probably comparable (especially since heterosexual activity is also apparently infrequent). In one study of wild Gray-capped Social Weavers, all sexual activity that was observed took place between males. In Red Bishops, approximately 6 percent of courtship bumble-flights are directed by one adult male toward another adult male; courtship of younger males probably occurs more often than this.

Orientation: Male Gray-capped Social Weavers that copulate with other males also mate and pair with females (and in fact may engage in homosexual activity while they are heterosexually paired). The same is true for some Sociable Weavers, although most males in this species mount both males and females, even if they are not paired. However, relatively few males participate in full heterosexual copulations, and those that do appear to have higher rates of homosexual activity as well. To the extent that they court or attempt to mount both males and females, some male Bishops are also bisexual. However, the males they pursue are usually indifferent, at best, to their approaches, indicating perhaps a more heterosexual orientation on their part.

In Gray-capped Social Weavers (and occasionally in Sociable Weavers), nonbreeding birds often help heterosexual pairs build their nest and feed their young. Some of these “helpers” are the pairs’ young from a previous season who are delaying their own reproductive careers, while others are fully adult birds (who help out in about 18 percent of all feedings). Some nonbreeding youngsters, however, do not help their parents. Sociable Weavers may participate in nonmonogamous heterosexual mountings (in addition to the homosexual matings described above). Although most birds are probably faithful to their partners, some males in captivity have been observed mounting and copulating with females other than their mates. Female Red Bishops occasionally refuse to allow a male to mount them, vigorously pecking and displaying threat postures to repel him. In addition, males often court Bishops of other species, who are not usually attracted by such interspecies displays. Finally, female Red Bishops have been observed cannibalizing both their own and others’ nests, eating some or all of the eggs.

Adult male Red-shouldered Widowbirds (Euplectes axillaris) also sometimes court younger males.

*asterisked references discuss homosexuality/transgender

*Collias, E. C, and N. E. Collias (1980) “Individual and Sex Differences in Behavior of the Sociable Weaver Philetairus socius.” In D. N. Johnson, ed., Proceedings of the Fourth Pan-African Ornithological Congress (Seychelles, 1976), pp. 243—51. Johannesburg: Southern African Ornithological Society.

*———(1978) “Nest Building and Nesting Behavior of the Sociable Weaver Philetairus socius.” Ibis 120:1—15.

*Collias, N. E., and E. C. Collias (1980) “Behavior of the Gray-capped Social Weaver (Psuedonigrita arnaudi) in Kenya.” Auk 97:213—26.

Craig, A. J. F. K. (1982) “Mate Attraction and Breeding Success in the Red Bishop.” Ostrich 53:246-48.

*———(1980) “Behavior and Evolution in the Genus Euplectes.” Journal für Ornithologie 121:144—61.

*———(1974) “Reproductive Behavior of the Male Red Bishop Bird.” Ostrich 45:149—60.

Craig, A. J. F. K., and A. J. Manson (1981) “Sexing Euplectes Species by Wing-Length.” Ostrich 52:9—16.

Maclean, G. L. (1973) “The Sociable Weaver.” Ostrich 44:176—261.

Roberts, C. (1988) “Little Bishop Birds (Euplectes orix) in a Lafia Garden—Tom, Dick, Harry, and Fred.” Nigerian Field 53:11—22.

Skead, C. J. (1959) “A Study of the Redshouldered Widowbird Coliuspasser axillaris axillaris (Smith).” Ostrich 30:13—21.

———(1956) “A Study of the Red Bishop.” Ostrich 27:112—26.

Woodall, P. F. (1971) “Notes on a Rhodesian Colony of the Red Bishop.” Ostrich 42:205—10.

Wattled Starlings usually associate in small, nomadic flocks, although up to a thousand birds may gather together to pursue locust swarms. Similarly, breeding colonies may contain thousands of nests when locusts are available, but usually birds nest in smaller groups containing a maximum of 400 pairs. Most individuals form monogamous pair-bonds, as do House Sparrows (who also generally nest in colonies). Brown-headed Cowbirds have a highly variable mating system: in many populations birds form (usually monogamous) pair-bonds, while in others they are promiscuous or form polygamous bonds with several individuals.

Behavioral Expression: Male Brown-headed Cowbirds sometimes solicit homosexual copulations from male House Sparrows. Cowbirds commonly invite birds of other species to preen them, but occasionally an interspecies encounter includes homosexual mounting when a House Sparrow is involved. This extraordinary behavior typically begins with a male Cowbird adopting a characteristic HEAD-DOWN posture next to a Sparrow, in which he bows his head, touching his lower bill to his breast feathers while crouching slightly and raising his wings a bit at the shoulders. The House Sparrow then mounts the Cowbird, grasping his head feathers in his beak while attempting to copulate. If he shows signs of leaving or lack of interest after a single mounting, the Cowbird will immediately resume the invitation posture next to him, insistently nudging the Sparrow with his head and persistently following him until he mounts again. This may continue for an extended time, with repeated homosexual mountings (five or more) occurring in a single session.

Homosexual courtships occasionally occur in Wattled Starlings. Males sometimes select another male as the object of their attentions, displaying to him with a number of stylized postures. Among these are the LATERAL DISPLAY, in which the male turns sideways and lets his wings hang down at his side (exposing their white feathers); the FRONTAL DISPLAY, where the courting male fluffs up his belly and back feathers, raising and quivering his wings while spreading his tail; and the distinctive VULTURE POSTURE, in which he stretches his entire body vertically while puffing out his breast feathers and tightly folding his wings against his sides like a vulture. A form of plumage transvestism also occurs in this species, in which some females develop a male appearance. Most males have a special seasonal nuptial plumage, growing two pendulous wattles from either side of their beaks and losing most of the feathers from their head, thereby exposing the yellow or black skin and two fleshy, comblike growths on the forehead. This feather loss has even been described as a form of “male pattern baldness” akin to the type of hair loss found in humans, and indeed it is regulated by male hormones (as is human baldness). While the majority of females never exhibit these plumage characteristics, a few females do acquire a male appearance with feather loss, wattles, and combs.

Frequency: Brown-headed Cowbirds regularly perform the head-down display toward other species in the wild, and approximately 36 percent of such displays are directed by male Cowbirds toward male House Sparrows; however, Sparrows respond with homosexual mounting probably only sporadically. Similarly, homosexual courtship is in all likelihood only an occasional occurrence in Wattled Starlings. About 2–10 percent of female Wattled Starlings are transgendered, exhibiting fairly complete wattles and/or baldness. Other females appear to fall along a continuum of plumage characteristics, with some individuals showing only partial wattle development or incomplete baldness.

Orientation: In all three of these species, not enough is yet known about the life histories of individuals participating in homosexual activity to determine their overall sexual orientation profiles. However, at least some male Wattled Starlings appear to preferentially select other males to court.

Although most heterosexual Wattled Starlings form monogamous pairs, occasionally males court and mate with females other than their mate. This may result in a female raising her young as a single parent if she is not paired to the male she mates with. The male sexual cycle is especially pronounced in this species, signaled by the seasonal development of wattles and baldness. House Sparrows often engage in multiple copulations during the same mating bout: a male may mount a female and achieve genital contact up to 30 times in rapid succession. In addition, promiscuous matings are quite common in this species: more than a quarter of all nests contain at least one chick sired by a bird other than its mother’s mate. Some of these are the result of forced matings that occur during COMMUNAL DISPLAYS, in which “gangs” of up to ten males chase a female, peck at her genitals, and try to mount her. Such displays and the associated sexual activity often take place during nonfertilizable periods as well. Courting male Cowbirds also frequently harass females, and on average only about 12 percent of heterosexual consortships in this species culminate in copulation. In pair-bonding populations of Brown-headed Cowbirds, about 16 percent of courtships are actually between birds not paired to one another, and some promiscuous matings occur as well. In both this species and House Sparrows, a few pairs switch mates during the breeding season, and a subset of birds (about 5–6 percent) are polygamous.

Large numbers of male Cowbirds are nonbreeders: more than half of all males in some populations are unpaired, and only a third of males actually copulate with females in some years. Brown-headed Cowbirds are also BROOD PARASITES, which means that females always lay their eggs in the nests of other bird species and take no part in raising their own young. Infanticide occurs in 9–12 percent of House Sparrow nests, often when a female who has lost her mate pairs with a new male (who pecks her young to death in order to father his own offspring). Females in polygamous trios also occasionally kill one another’s nestlings. Sometimes, however, a female whose mate has been replaced by an infanticidal male will stop laying eggs (by interrupting or delaying ovulation) in order not to lose any more young, and some replacement males adopt rather than kill their mate’s young.

Male Sharp-tailed Sparrows (Ammodramus caudacutus), a North American species, sometimes mount other males. Adolescent male Yellow-rumped Caciques (Cacicus cela), a South American blackbird, frequently mount fledglings of both sexes. Sexual behavior toward these younger birds is usually part of an overall pattern of harassment, in which the adolescent males (often in groups) chase, peck, attack, and sometimes even knock fledglings from their perches (often resulting in their death by drowning if they fall into water). About 36 percent of such harassments (and the associated sexual behavior) involve same-sex interactions.

*asterisked references discuss homosexuality/transgender

Craig, A. J. F. K. (1996) “The Annual Cycle of Wing Moult and Breeding in the Wattled Starling Creatophora cinerea.” Ibis 138:448—54.

Darley, J. A. (1978) “Pairing in Captive Brown-headed Cowbirds (Molothrus ater).” Canadian Journal of Zoology 56:2249—52.

*Dean, W. R. J. (1978) “Plumage, Reproductive Condition, and Moult in Non-Breeding Wattled Starlings.” Ostrich 49:97-101.

Friedmann, H. (1929) The Cowbirds: A Study in the Biology of Social Parasitism. Springfield, Ill.: Charles C. Thomas.

*Greenlaw, J. S., and J. D. Rising (1994) “Sharp-tailed Sparrow (Ammodramus caudacutus).” In A. Poole and F. Gill, eds., The Birds of North America: Life Histories for the 21 st Century, no. 112. Philadelphia: Academy of Natural Sciences; Washington, D.C.: American Ornithologists’ Union.

*Griffin, D. N. (1959) “Apparent Homosexual Behavior Between Brown-headed Cowbird and House Sparrow.” Auk 76:238—39.

*Hamilton, J. B. (1959) “A Male Pattern Baldness in Wattled Starlings Resembling the Condition in Man.” Annals of the New York Academy of Sciences 83:429-47.

Laskey, A. R. (1950) “Cowbird Behavior.” Wilson Bulletin 62:157-74.

Liversidge, R. (1961) “The Wattled Starling (Creatophora cinerea [Menschen]).” Annals of the Cape Provincial Museums 1:71—80.

Lowther, P. E. (1993) “Brown-headed Cowbird (Molothrus ater).” In A. Poole, P. Stettenheim, and F. Gill, eds., The Birds of North America: Life Histories for the 21st Century, no. 47. Philadelphia: Academy of Natural Sciences; Washington, D.C.: American Ornithologists’ Union.

Lowther, P. E., and C. L. Cink (1992) “House Sparrow (Passer domesticus).” In A. Poole, P. Stettenheim, and F. Gill, eds., The Birds of North America: Life Histories for the 21 st Century, no. 12. Philadelphia: Academy of Natural Sciences; Washington, D.C.: American Ornithologists’ Union.

Møller, A. P. (1987) “House Sparrow, Passer domesticus, Communal Displays.” Animal Behavior 35:203—10.

*Robinson, S. K. (1988) “Anti-Social and Social Behavior of Adolescent Yellow-rumped Caciques (Icteri-nae: Cacicus cela).” Animal Behavior 36:1482-95.

Rothstein, S. I. (1980) “The Preening Invitation or Head-Down Display of Parasitic Cowbirds: II. Experimental Analysis and Evidence for Behavioral Mimicry.” Behavior 75:148—84.

Rothstein, S. I., D.A. Yokel, and R. C. Fleischer (1986) “Social Dominance, Mating and Spacing Systems, Female Fecundity, and Vocal Dialects in Captive and Free-Ranging Brown-headed Cowbirds.” Current Ornithology 3:127—85.

Scott, T. W, and J. M. Grumstrup-Scott (1983) “Why Do Brown-headed Cowbirds Perform the Head-Down Display?” Auk 100:139—48.

*Selander, R. K., and C. J. La Rue, Jr. (1961) “Interspecific Preening Invitation Display of Parasitic Cowbirds.” Auk 78:473—504.

*Sontag, W.A., Jr. (1991) “Habitusunterschiede, Balzverhalten, Paarbildung, und Paarbindung beim Lap-penstar Creatophora cinerea [Behavior Differences, Courtship, Pair Formation, and Pair Bonding in the Wattled Starling].” Acta Biologica Benrodis 3:99—114.

———(1978/79) “Remarks Concerning the Social Behavior of Wattled Starlings, Creatophora cinerea (Menschen).” Journal of the Nepal Research Center 2/3:263—68.

Teather, K. L., and R. J. Robertson (1986) “Pair Bonds and Factors Influencing the Diversity of Mating Systems in Brown-headed Cowbirds.” Condor 88:63—69.

Uys, C. J. (1977) “Notes on Wattled Starlings in the Western Cape.” Bokmakierie 28:87—89.

Veiga, J. P. (1993) “Prospective Infanticide and Ovulation Retardation in Free-Living House Sparrows.” Animal Behavior 45:43—46.

———(1990) “Infanticide by Male and Female House Sparrows.” Animal Behavior 39:496-502.

Wetton, J. H., and D.T. Parkin (1991) “An Association Between Fertility and Cuckoldry in the House Sparrow, Passer domesticus.” Proceedings of the Royal Society of London, Series B 245:227-33.

Yokel, D. A. (1986) “Monogamy and Brood Parasitism: An Unlikely Pair.” Animal Behavior 34:1348—58.

Yokel, D. A., and S. I. Rothstein (1991) “The Basis for Female Choice in an Avian Brood Parasite.” Behavioral Ecology and Sociobiology 29:39—45.

All three of these Crow species are quite gregarious, often associating in flocks and communal roosts. Individuals generally form long-term mated pairs, and Jackdaws usually nest in colonies. Magpies sometimes participate in remarkable group displays known as CEREMONIAL GATHERINGS, noisy aggregations that may be related to territory acquisition.

Behavioral Expression: Black-billed Magpies sometimes court and form pair-bonds with birds of the same sex. Partners include adult males with younger or juvenile males (less than one year old), or else two females or two males of the same age, usually juveniles but also sometimes two adult males. A typical homosexual courtship—for example, between two males—begins with one bird ritually BEGGING the other by crouching in front of him and flapping or quivering his wings while uttering a begging call. The other male responds by hopping in tight circles around him, fluffing up his white feathers and flicking his wings; he may also BABBLE-SING, a varied combination of warbling, chattering, and yelping notes. The circling male often adopts a TILTING posture, in which he points his head and tail sideways toward the other male. If the male he is courting flies off, a courtship pursuit known as CHASE-HOPPING may develop, in which one male follows the other while alternately flying and hopping. Sometimes the two birds also HOVER-FLY, one in front of the other, using a rhythmic, undulating flight pattern. The same series of behaviors is seen in courtships between females (as well as in heterosexual interactions). Homosexual courtship sessions can last for up to half an hour. After courting, two birds of the same sex may form a pair-bond. Paired birds stay near each other, follow one another, and often cooperate in evicting intruders from their territory. They also frequently sit close together and preen one another or engage in mutual BILLING, in which they affectionately nibble at each other’s beak. Sometimes, homosexual mates also pull or nibble on the same leaf or twig and pass it back and forth between them; this is known as TUGGING. Same-sex pair-bonds are generally of shorter duration than adult heterosexual bonds and last from a few days to several months. However, adult males sometimes form longer-lasting homosexual pairs, and the two birds may even build a nest together (which typically takes five to seven weeks to construct).

Female Jackdaws occasionally develop pair-bonds with other females. In some cases, an older female pairs with a younger one, and the two build a nest together even though the juvenile bird is too young to lay eggs. Later, they might construct a unique “double nest” consisting of two adjacent cups and lay infertile eggs in both cups. Sometimes, a homosexual pair is joined by a male, who may bond with one or both of the females to form a bisexual trio; in this way, the females can lay fertilized eggs. However, they are often unable to successfully care for their offspring, precisely because their bond to each other means that they try to stay together all the time. The two females incubate their eggs and brood their youngsters simultaneously, each sitting on one cup. When the male arrives for his shift, however, they both depart together, leaving the male to try to cover and protect both sets of eggs or nestlings at the same time (which he is usually unable to do). Sometimes, a bi-sexual trio forms when a female joins a heterosexual pair and develops a strong bond with the female partner. The two females engage in courtship and pair-bonding activities such as mutual preening or COURTSHIP-FEEDING, in which one partner begs the other by crouching, fluttering her wings, and quivering her tail. Both females might mate with the male and lay fertile eggs, although the bond between them can end up being stronger than the original heterosexual bond. In fact, in one case the female partners were not able to properly care for their young because the male denied the female “interloper” access to the nestlings. Homosexual bonds also sometimes develop between widowed and nonbreeding females. In these cases, females that lose their male partners during the breeding season may attract unmated females to pair with them; some of these widows are mothers, while others have no offspring. Unlike bisexual trios, which may remain together for years, these female bonds appear to be more transitory, usually lasting only for several weeks until the breeding season is over.

Female homosexual pairs also occasionally occur in Ravens, including incestuous bonds between yearling sisters. Birds in same-sex pairs engage in intense courtship activity similar to heterosexual pairs, such as mutual preening and courtship-feeding.

Frequency: Among Jackdaws in the wild, approximately 5 percent of trios include bonding between the two female partners, while about 10 percent of widowed females form homosexual pairs. Overall, though, same-sex bonds probably represent no more than 1 percent of all pairs/trios. Homosexual activity occurs sporadically in Black-billed Magpies and Ravens as well: about 1 percent of nesting pairs of Magpies, for example, consist of two males. Although homosexual copulations between Magpies have not yet been recorded, heterosexual matings are also infrequently observed (only 9 male-female copulations, for example, were recorded during one 300—hour study period).

Orientation: Homosexual behavior is most prevalent among younger Black-billed Magpies, some of whom also court members of the opposite sex; many of these birds go on to form heterosexual attachments when they become adults, but most are nonbreeders during the time of their same-sex activities. Some adult males, however, continue to court younger males or pair with other adult males. In Jackdaws and Ravens many different forms of bisexuality occur. Some females are simultaneously bonded to both males and females, and such trios may develop out of either an initial heterosexual or homosexual pair-bond. Some females are sequentially bisexual, developing same-sex bonds only after losing their male partners. However, those Jackdaw females who enter into homosexual pairs as nonbreeders may have no prior (and perhaps no subsequent) heterosexual experience.

Black-billed Magpies and Jackdaws participate in a number of nonprocreative heterosexual activities. Birds sometimes copulate long after fertilization has taken place—even during incubation or chick-rearing—while courtship and mounting may occur well in advance of the breeding season in Magpies. In both species, birds form pair-bonds as juveniles, long before they are able to breed. Several alternatives to the monogamous pair and nuclear family are also to be found in these species of Crows. In Black-billed Magpies, for example, courtship and copulations with birds outside of the pair-bond can be more frequent than within-pair matings. In addition, some pairs get divorced: about half of all males and just under two-thirds of females change mates, and some may pair with up to three different partners over the course of their lives. Other Magpies, however, do remain in lifelong, faithful pair-bonds. About 6–10 percent of adult Jackdaw pairs, and a third of all juvenile pairs, get divorced. Polygamous trios also sometimes develop in Magpies (1–2 percent of bonds), but are fairly common in Jackdaws, comprising about 14 percent of all bonds. These usually result from an unpaired female joining an existing male-female pair; unlike the bisexual trios described above, she usually bonds only with the male of the pair, not the female. Occasionally, she may oust the former female and start a new family with the male; frequently, however, the newcomer female does not breed even if she remains in the trio for several years.

Nonbreeding couples also occur in Jackdaws and Ravens, as well as a significant population of single, nonreproducing birds. The latter are found in Magpies as well, where they make up 20–60 percent of the population and may be solitary or form their own flocks. In addition, about half of all Magpies that survive to adulthood leave no descendants (even if they try to breed). Some nonbreeding Jackdaw pairs—or couples who have tried unsuccessfully to breed—end up harassing breeding pairs by invading their nests, fighting with them, and even attacking and occasionally killing their young with vicious pecks. Nearly a third of all breeding pairs in some populations are harassed in this way. Cannibalism of young and eggs by neighboring breeding pairs also sometimes occurs in Jackdaws. Magpies and Ravens occasionally adopt unrelated youngsters when they pair with a bird that has lost its mate. Magpie families also sometimes foster-parent chicks as a result of the extraordinary phenomenon of “egg transfer”: in some populations, up to 8 percent of nests contain a foreign Magpie egg, but not as a result of being laid there. Rather, another Magpie has physically carried its own egg in its beak to the new nest, placing it there to hatch and be raised by the host parents. Stealing and cannibalism of young or eggs has also been reported among Black-billed Magpies: about 7 percent of nests are robbed by other Magpies. In addition, at least 30 percent of nestlings die of starvation as a result of competition from their siblings, or from direct attacks or cannibalism by their nest-mates.

Homosexual courtship occurs in some species of Jays (closely related to Crows), so far observed only in captivity. Male Gray-breasted or Mexican Jays (Aphelocoma ultramarina), a species found in the American Southwest and Mexico, have been seen COURTSHIP-FEEDING younger males in mixed-sex groups. This behavior—also part of heterosexual courtships—involves one male offering the other a food item; the latter accepts it while quivering his wings, crouching, and uttering a low kwa kwa kwa call. After eating the food or storing it in a cache, he may follow the other male to repeat the episode. Female San Bias Jays (Cyanocorax san-blasianus) of Mexico have been known to court other females in same-sex groups in captivity, using the SOTTO VOCE SONG DISPLAY. While making soft, throaty vocalizations, one female sidles up to the other on a perch with her tail raised and belly feathers fluffed.

*asterisked references discuss homosexuality/transgender

Antikainen, E. (1981) “The Breeding Success of the Jackdaw Corvus monedula in Nesting Cells.” Ornis Fennica 58:72–77.

*Baeyens, G. (1981a) “Magpie Breeding Success and Carrion Crow Interference.” Ardea 69:125–39.

———(1981b) “Functional Aspects of Serial Monogamy: The Magpie Pair-Bond in Relation to Its Territorial System.” Ardea 69:145–66.

*———(1979) “Description of the Social Behavior of the Magpie (Pica pica).” Ardea 67:28–41.

Birkhead, T. (1991) The Magpies: The Ecology and Behavior of Black-billed and Yellow-billed Magpies. London: T. and A. D. Poyser.

Birkhead, T., and J. D. Biggins (1987) “Reproductive Synchrony and Extra-Pair Copulation in Birds.” Ethology 74:320–34.

Birkhead, T., S. F. Eden, K. Clarkson, S. F. Goodburn, and J. Pellatt (1986) “Social Organization of Magpies Pica pica.” Ardea 74:59–68.

Buitron, D. (1988) “Female and Male Specialization in Parental Care and Its Consequences in Black-billed Magpies.” Condor 90:29–39.

———(1983) “Extra-Pair Courtship in Black-billed Magpies.” Animal Behavior 31:211-20.

Coombs, F. (1978) The Crows: A Study of the Corvids of Europe. London: B. T. Batsford.

Dhindsa, M. S., and D. A. Boag (1992) “Patterns of Nest Site, Territory, and Mate Switching in Black-billed Magpies (Pica pica).’ Canadian Journal of Zoology 70:633–40.

Dunn, P O., and S. J. Hannon (1989) “Evidence for Obligate Male Parental Care in Black-billed Magpies.” Auk 106:635–44.

*Hardy, J. W. (1974) “Behavior and Its Evolution in Neotropical Jays (Cissilopha).” Bird-Banding 45:253–68.

*———(1961) “Studies in Behavior and Phylogeny of Certain New World Jays (Garrulinae).” University of Kansas Science Bulletin 42:13–149.

Jerzak, L. (1995) “Breeding Ecology of an Urban Magpie Pica pica Population in Zielona Góra (SW Poland).” Acta Ornithologica 29:123–33.

*Lorenz, K. (1972) “Pair-Formation in Ravens.” In H. Friedrich, ed., Man and Animal: Studies in Behavior, pp. 17–36. New York: St. Martin’s.

*———(1935) “Der Kumpan in der Umwelt des Vögels.” Journal für Ornithologie 83:10–213, 289–413. Reprinted as “Companions as Factors in the Bird’s Environment.” In K. Lorenz (1970) Studies in Animal and Human Behavior, vol.1, pp. 101–258. Cambridge, Mass.: Harvard University Press.

Ratcliffe, D. (1997) The Raven: A Natural History in Britain and Ireland. London: T. and A. D. Poyser.

Reynolds, P. S. (1996) “Brood Reduction and Siblicide in Black-billed Magpies (Pica pica).” Auk 113:189–99.

*Röell, A. (1979) “Bigamy in Jackdaws.” Ardea 67:123–29.

———1978) “Social Behavior of the Jackdaw, Corvus monedula, in Relation to Its Niche.” Behavior 64:1–124.

Trost, C. H., and C. L. Webb (1986) “Egg Moving by Two Species of Corvid.” Animal Behavior 34:294–95.

BIRDS OF PARADISE, BOWERBIRDS, AND OTHERS

Male Raggiana’s Birds of Paradise perform courtship displays on communal “courts” or LEKS (located in tree branches) in groups of up to eight individuals at a time; females visit the leks in pairs or small groups. Male Victoria’s Riflebirds display singly. Both species have a polygamous or promiscuous mating system, in which males copulate with more than one female but do not participate in any parental duties.

Behavioral Expression: Male Victoria’s Riflebirds sometimes court younger males with a series of spectacular displays (also seen in heterosexual courtships). Adult males attract individuals of both sexes to their display perches by repeatedly calling with a loud yass note and opening their bills to expose the bright yellow mouth interior. When an interested male (or female) approaches, the courting male begins his CIRCULAR WINGS AND GAPE display, in which he fans his wings to form a perfect circle with the tips meeting above his head while simultaneously raising and lowering his body. The wing circle is held vertically as he gapes his bill and presents his iridescent throat feathers to the other male. If the latter lands on the display perch, the courtship progresses to its final phase, the astounding ALTERNATE WINGS CLAP display. The adult male begins swaying and twisting his body from side to side, alternately raising and lowering each wing so that they “clap” with a dull, thudding sound when they meet above his head. Gradually the wings are brought forward while being clapped so that they encircle the younger male. The tempo of the display is increased until, at its climax, the wing-clapping reaches an astounding speed—each wing alternately encircles the observing male at a rate approaching twice a second. The courted male becomes mesmerized by the brilliant metallic bluish green throat shield of the displaying male as it is jerked violently back and forth, and he may respond by simultaneously performing his own alternate wings clap display. If both males are displaying, they alternate wing movements, gradually crouching while arching their heads back and quivering all over. They often perform several bouts of mutual display with brief rests between each. Occasionally one male briefly mounts the other; full copulation does not usually occur, though, since the mounted male often simply flies away from underneath the male mounting him.

Courtship displays between female Raggiana’s Birds of Paradise involve some of the same postures and movements used in heterosexual courtship in this species. One female arches her wings above her back and then claps them against her sides, all the while bobbing up and down and erecting the feathers on her back and flanks as she dances in front of the other female. Every now and then she makes an ur, ur call, and she may even hang upside down on a branch while flicking her wings and calling. This dramatic pose is held for a minute or more at a time. Males use this inverted posture to show off their orange “tail” plumes during courtship, but females perform this display even though they do not have such ornate feathers. Sometimes two females engage in mutual display, facing each other while holding their wings stiffly above their backs and bobbing.

Frequency: Courtship displays between male Victoria’s Riflebirds occur fairly often at some times of the year, especially during the postmolting period in February and March. Although homosexual mountings are not common in this species, opposite-sex matings have in fact been seen only a few times during more than a hundred courtship displays observed in the wild.

Orientation: At least some male Victoria’s Riflebirds are functionally bisexual, courting and attempting to mate with both males and females. In Raggiana’s Bird of Paradise, courtship display between females has so far only been observed in captivity in the absence of males, so this behavior may be the expression of a potential or “latent” bisexual capacity. More detailed field observations and life histories are required, though, before any definitive statements can be made regarding the sexual orientation of individuals that engage in this activity.

Only about 11 percent of lek visits by female Raggiana’s Birds of Paradise actually result in heterosexual mating. More often than not, a courtship interaction is broken off by a female before copulation occurs. In addition, males often chase females and behave aggressively toward them on the lek, which deters them from participating in sexual interactions. When mating does take place, the female often mounts the male prior to copulation. Such REVERSE mounts are then followed by a display in which the male appears to pummel his partner with his wing. The female crouches on her perch absorbing the blows for 20—35 seconds, after which copulation occurs. Nonreproductive matings also take place outside of the breeding season. Many males may delay breeding up to five or more years once becoming sexually mature, since they do not generally acquire their ornate plumage (used in courtship displays) for several years.

Male Greater Birds of Paradise (Paradisaea apoda), a species closely related to Raggiana’s, also sometimes court and mount younger males.

* asterisked references discuss homosexuality/transgender

Beehler, B.M. (1989) “The Birds of Paradise.” Scientific American 261(6):116–23.

———(1988) “Lek Behavior of the Raggiana Bird of Paradise.” National Geographic Research 4:343–58.

*Bourke, P. A., and A. F. Austin (1947) “The Atherton Tablelands and Its Avifauna.” Emu 47:87–116.

Davis, W. E., Jr., and B. M. Beehler (1994) “Nesting Behavior of a Raggiana Bird of Paradise.” Wilson Bulletin 106:522–30.

*Frith, C. B. (1997) Personal communication.

———(1981) “Displays of Count Raggi’s Bird-of-Paradise Paradisaea raggiana and Congeneric Species.” Emu 81:193–201.

*Frith, C. B., and W. T. Cooper (1996) “Courtship Display and Mating of Victoria’s Riflebird Ptiloris victoriae with Notes on the Courtship Displays of Congeneric Species.” Emu 96:102–13.

Frith, C. B., and D. W. Frith (1995) “Notes on the Nesting Biology and Diet of Victoria’s Riflebird Ptiloris victoriae.” Emu 95:162–74.

Gilliard, E. T. (1969) “Queen Victoria Rifle Bird” and “Count Raggi’s Bird of Paradise.” In Birds of Paradise and Bower Birds, pp. 112–17,222–29. Garden City, N.Y.: Natural History Press.

Lecroy, M. (1981) “The Genus Paradisaea—Display and Evolution.” American Museum Novitates 2714:1–52.

*Mackay, M. (1981) “Display Behavior by Female Birds of Paradise in Captivity.” Newsletter of the Papua New Guinea Bird Society 185/186 (November-December):5.

Regent Bowerbirds have a polygamous or promiscuous mating system: males court and mate with multiple partners on display territories (see below). Following the mating season birds often associate in cosexual flocks of 10—20 individuals.

Behavioral Expression: Male Regent Bowerbirds build elaborate structures called BOWERS, in which they court both males and females. Bowers built by adult males form an “avenue” on the ground consisting of two parallel walls of twigs—10–12 inches high and 7–8 inches long—which are inserted into a platform of twigs on the ground. In some bowers the walls form a sort of arched walkway, while other bowers have triangular-shaped walls of different sizes. The bower is usually decorated with a dozen or so “display objects” or ornaments that are often selected for their color and strewn on the platform. These include brown snail shells, berries, green or purplish leaves, brown fruits and seeds, cicada husks, occasionally a yellow or pink flower petal, and even scavenged pieces of blue plastic. Remarkably, some birds also “paint” the walls of their bowers by applying, with their bills, macerated plant material mixed with saliva, giving some of the twigs a yellowish green coating. Adult males display in their bowers to females and younger males by flicking their wings and bowing their heads to show off their brilliant orange and yellow neck feathers. Sometimes they also ritually “present” display objects to the bird they are courting by picking up one of the ornaments from the avenue and holding it in their bill while facing their partner.

Juvenile males also build bowers and court both males and females. In some cases, they use the same bower shapes and displays as adults, but in other cases they utilize their own patterns, some of which may be unique to same-sex interactions. Some bowers built by younger males are more in the form of a horseshoe—open only at one end—with the sticks woven horizontally rather than vertically. When courtship-displaying to an adult male, the younger male enters the bower and squats with his tail toward the entrance. The adult male then rushes toward the juvenile, who is behind the closed end of the bower, or sometimes goes around to the entrance and tweaks the younger male’s tail. When courting other juvenile birds of both sexes, young males may perform a dance in the center of the bower, picking up an ornament and bobbing up and down with half-opened wings, then tossing the object over the bower wall. The bird(s) watching this display sweep and brush the ground with their wings.

Many younger males are transvestite, having a plumage coloration that more closely resembles that of adult females than adult males. It takes males up to seven years to develop the full yellow, orange, and black feathers typical of adult males, and during that time many actually exhibit plumages that are intermediate between the adult male and female patterns.

Frequency: Among adult male Regent Bowerbirds, 15 percent of their bower courtship time is spent displaying to other males, while 28 percent of juvenile males’ display time is same-sex.

Orientation: Regent Bowerbirds that court other males are probably bisexual, since they display to birds of both sexes.

A large segment of the male Regent Bowerbird population is nonbreeding: only about a third of all adult males maintain bowers, and of those that do, only a fraction actually mate with females. In addition, heterosexual courtship interactions rarely result in copulation: in only about 7 percent of female visits to bowers does mating actually take place, since the female often leaves while the male is displaying (and in 10 percent of female visits the male does not display at all).

Adult male Satin Bowerbirds (Ptilonorhynchus violaceus) from Australia have also been observed performing courtship displays toward younger males.

*asterisked references discuss homosexuality/transgender

Chaffer, N. (1932) “The Regent Bird.” Emu 32:8–11.

*Gilliard, E. T. (1969) “Australian Regent Bower Bird.” In Birds of Paradise and Bower Birds, pp. 335–44. Garden City, N.Y.: Natural History Press.

Goddard, M. T. (1947) “Bower-Painting by the Regent Bower-bird.” Emu 47:73–74.

*Lenz, N. (1994) “Mating Behavior and Sexual Competition in the Regent Bowerbird Sericulus chrysocephalus.” Emu 94:263–72.

*Marshall, A. J. (1954) “Satin Bower-bird, Ptilonorhynchus violaceus (Vieillot)” and “Regent Bower-bird, Sericulus chrysocephalus (Lewin).” In Bower-birds: Their Displays and Breeding Cycles, pp. 26–71, 109–18. Oxford: Oxford University Press.

*Phillipps, R. (1905) “The Regent Bird (Sericulus melinus).” Avicultural Magazine (new series) 4:51—68, 88—96, 123—31.

Plomley, K. F. (1935) “Bower of the Regent Bower-bird.” Emu 34:199.

Adult male Superb Lyrebirds establish territories on which they build earth mounds three to five feet wide, used as platforms for courtship displays. The mating system is polygamous or promiscuous: birds mate with multiple partners without developing long-lasting pair-bonds, and males do not contribute to raising their offspring. Adolescent Lyrebirds often associate in small groups, sometimes consisting only of males.

Behavioral Expression: Male Superb Lyrebirds often court younger (adolescent) males on encountering them either in their groups or singly. The adult male closely follows the younger male, sometimes for hours at a time, periodically performing the WING-RAISING DISPLAY, in which he lifts and fans one wing toward his partner. With neck outstretched, he serenades the other male with a variety of extraordinary vocalizations, such as “whisper-song”; chortling; a call that can be rendered phonetically as clonk clonk clickety clickety click; another vocalization that sounds like the grinding of a pair of scissors; as well as uncanny imitations of other birds’ songs. Sometimes the courtship progresses to spectacular displays of the male’s elongated and stunningly beautiful tail feathers. In the dazzling FULL-FACE DISPLAY, for example, the older male arches his tail forward over his head and spreads the silvery filamentary feathers, hiding his body behind a gossamer fan framed by the elegant lyre-shaped, chestnut-striped outer tail feathers (for which the bird is named). Often the entire tail is vibrated to create a shimmering effect directed toward the other male. This may be followed by the INVITATION DISPLAY, in which the male almost “closes up” his quivering tail fan while still holding it forward (the feather tips almost touching the ground in front of him), all the while repeating a blick blick blick call. Occasionally, the younger male being courted by an adult is his own offspring. Adult males also sometimes mount adolescent males, even during the nonbreeding season when the adult bird is molting and has shed his elaborate tail plumes. Genital contact probably does not occur, though, since the younger male usually does not facilitate the interaction.

Adolescent male Lyrebirds also sometimes mount one another as well as particpate in homosexual courtship displays. Courtship between younger males is usually mutual, with both birds singing and displaying to one another. Occasionally an adult and an adolescent male also engage in mutual display, and adult females (in captivity) have been observed performing a similar courtship display to each other. Typically, the two adolescent males circle around each other on a display mound, tails raised in a fan shape with their feathers intermingled and beaks nearly touching while performing a vocal duet. One male may also perform a full-face or invitation display, and his partner sometimes runs underneath his outstretched tail the way a female does during heterosexual courtship. Sometimes the two males engage in what appears to be a form of COURTSHIP-FEEDING: in response to begging from his partner, one male regurgitates a worm or other food item as an offering to the other, who promptly eats it. This behavior appears to be unique to homosexual courtships. Two younger males often form a “companionship”: in addition to courting each other, they follow one another, feed together (even digging in the same hole for food items), roost next to each other, and share bathing pools. These male pair-bonds usually last for only a few days, and adolescent males often form multiple serial attachments of this sort.

Frequency: Homosexual courtship occurs fairly often in Superb Lyrebirds. Adult males approach groups of adolescent males approximately once every three days during the breeding season and roughly once every day and a half outside the breeding season, and 93 percent of these encounters include courtship. In comparison, heterosexual encounters occur about four times as often as homosexual encounters during the breeding season, and about twice as often outside the breeding season. Adult males associate with adolescent males (in groups or singly) more than half of the time they are away from their display mounds. Same-sex mounting occurs less frequently than courtship interactions between males.

Orientation: Most adult males are functionally bisexual, courting and mounting both females and younger males. Adolescent males appear to be more exclusively homosexual: most individuals form same-sex companionships and engage in homosexual courtship (and sometimes mounting) for several years prior to mating heterosexually. Some females probably have a bisexual potential that manifests itself in the absence of males (for example, in captivity).

Male and female Superb Lyrebirds lead largely separate lives. Other than brief encounters during the breeding season for courtship and copulation, the two sexes rarely interact: only about 8—10 percent of all Lyrebird sightings are of males and females together. Because males do not contribute at all to parenting, incubation and chick-raising often become burdensome for females—and by extension, potentially harmful for the eggs and/or chicks. During the early stages of incubation, females regularly leave their eggs unattended during the day for up to seven hours at a time to feed, causing the egg temperature to drop dramatically. Overall, females are relatively “inattentive” parents, incubating their eggs for only about 27—45 percent of the available daylight hours; this is significantly less than in other perching birds, who generally spend 60—80 percent. Because the eggs are laid and incubated during the coldest months of winter, they are consequently exposed to dangerously low (sometimes even sub-freezing) temperatures that generally slow embryonic development. After hatching, nestlings occasionally die from overexposure when their mother has been away from the nest for too long.

*asterisked references discuss homosexuality/transgender

Kenyon, R. F. (1972) “Polygyny Among Superb Lyrebirds in Sherbrooke Forest Park, Kallista, Victoria.” Emu 72:70—76.

Lill, A. (1986) “Time-Energy Budgets During Reproduction and the Evolution of Single Parenting in the Superb Lyrebird.” Australian Journal of Zoology 34:351—71.

*———(1979a) “An Assessment of Male Parental Investment and Pair Bonding in the Polygamous Superb Lyrebird.” Auk 96:489—98.

———(1979b) “Nest Inattentiveness and Its Influence on Development of the Young in the Superb Lyrebird.” Condor 81:225—31.

Reilly, P. (1988) The Lyrebird: A Natural History. Kensington, Australia: New South Wales University Press.

*Smith, L. H. (1996-97) Personal communication.

*———(1988) The Life of the Lyrebird. Richmond, Australia: William Heinemann.

(1982) “Molting Sequences in the Development of the Tail Plumage of the Superb Lyrebird, Menura novae-hollandiae.” Australian Wildlife Research 9:311—30.

*———(1968) The Lyrebird. Melbourne: Lansdowne Press.

Watson, I. M. (1965) “Mating of the Superb Lyrebird, Menura novae-hollandiae.” Emu 65:129—32.

FLIGHTLESS BIRDS

Ostriches associate in flocks and frequently form sex-segregated groups. All-male flocks may contain up to 40 individuals, many of them juveniles, who travel with each other for long periods. Emus generally associate in pairs or groups of 3–10 birds, while Greater Rheas gather in flocks of 15–40 birds outside of the mating season. All three species have a wide variety of mating systems (discussed below). These are notable for their various forms of POLYANDRY (females mating with several males) and the fact that—in Emus and Greater Rheas—all incubation and chick-rearing is performed by males without any help from females.

Behavioral Expression: Male Ostriches perform a homosexual courtship dance to each other that is distinct from heterosexual interactions. Same-sex courtships consist of a sequence of three activities, performed by sexually mature adult males in full nuptial plumage (black-and-white feathers, with a red flush on the face and legs). First, there is a dramatic APPROACH in which one male runs rapidly toward his chosen partner—often achieving speeds of 25–30 mph—and stops abruptly just short of the other male. Then he launches into frenzied PIROUETTE DANCING, a high-speed, energetic circling in place beside his partner. This whirling may occur in a series of bursts, each lasting for several minutes. Finally, in KANTLING, the male drops to the ground next to his partner and rocks steadily from side to side, fluffing out his tail and sweeping the ground with his wings in an exaggerated fashion. All the while, he twists his head and neck in a continuous corkscrew action and repeatedly inflates and deflates his throat. The male being displayed to may acknowledge the dance with his posture, or he may simply maintain a calm stance devoid of alarm or aggression. Homosexual courtships are distinct from heterosexual ones in a number of respects: neither the running approach nor pirouette dancing occur in male-female interactions. Kantling is performed in heterosexual contexts but differs because it is usually accompanied by singing (when males display to females, they frequently produce a booming call), and it is significantly shorter. Same-sex displays last for 10—20 minutes, while opposite-sex ones rarely exceed three minutes. Also, symbolic feeding and nest-site displays are components of heterosexual but not homosexual courtships.

Although no copulation takes place between courting male Ostriches, homosexual mating has been observed in pairs of male Emus. A sexual interaction begins with one male approaching the other, stretching his neck upward and erecting his neck feathers so that they stand out horizontally, while grunting deeply. The two birds begin following and chasing each other; if the male who initiated the activity is behind the other, he may make treading movements with his feet, indicating his intention to mount the other. Often, however, it is the initiating male who lies flat on the ground as an invitation for the other male to mount. The males may also take turns mounting each other. The mounting male lies down behind his partner, resting his breast on the other’s rump, and uses his heels to slide forward until he covers most of the other male. While copulation is taking place, the mountee makes soft grunting noises (not usually heard during heterosexual matings), and the mounter gently toys with the feathers on his partner’s upper back. After mating, his erect penis is often visible: the male Emu, along with other ratites, is one of the few birds in the world that has a penis (most male birds simply have a cloacal, or genital, opening).

Male Emus also sometimes coparent with each other: two (and occasionally three) males may attend one nest at the same time, incubating all the eggs together. Such nests often contain SUPERNORMAL CLUTCHES of 14–16, and sometimes more than 20, eggs. This is over twice the number found in nests attended by single males, probably because more than one female has laid in them. Unlike single fathers, male coparents are able to take a break from incubating while their partner sits on the nest; they also sometimes roll the eggs between them while on the nest together. Although they are probably not sexually involved with one another, the two fathers cooperate in raising their chicks together, calling to them with “purr-growls” and jointly defending them from predators. A similar phenomenon is found in Greater Rheas: pairs of males occasionally sit on “double nests” that are close to or touching one another; they incubate the eggs together and jointly parent the chicks when they hatch. Most such nests begin as standard nests with only one male incubating, after which another male joins him and begins transferring eggs to his half of the nest; later, eggs may be transferred back and forth between the twin nests. Unlike Emu nests belonging to male coparents, Rhea double nests usually have a combined number of eggs that is the same as for single nests. Male coparents are different from male nest helpers, which are also found in Rheas. About a quarter of breeding males are assisted by an adolescent male, who incubates and raises (on his own) a clutch of eggs fathered by the adult while the latter goes off to start a new family. This differs from male coparenting in that the two nests are widely separated from one another, each contains the full clutch size of a single nest, the two males never share parenting duties, and the helper is always an adolescent male.

Female Ostriches are occasionally transvestite, having full black-and-white male plumage (along with underdeveloped ovaries).

Frequency: Homosexual courtship in Ostriches is quite common in some populations, occurring two to four times a day (usually in the morning). Sexual behavior between male Emus has so far only been observed in captivity, but it does occur repeatedly between partners. Among Greater Rheas, joint parenting between males occurs in about 3 percent of all nests; Emu coparenting probably occurs at a similar rate.

Orientation: In Ostriches, 1–2 percent of all adult males engage in homosexual courtship in some populations. Male Ostriches who court other males typically ignore any females that may be present; they are probably solitary birds that participate in little, if any, heterosexual interactions. Most Emus and Rheas that participate in male coparenting have probably mated and/or paired with females earlier in the season prior to parenting with another male. Male Emus may also have a latent capacity for bisexuality, as evidenced by the occurrence of sexual behavior between captive males (at least one of whom had previously mated heterosexually). However, individual life histories and the full patterns of sexual orientation have not yet been systematically studied in this species.

Heterosexual mating in Ratites occurs in the context of an extraordinary variety of complex social arrangements that deviate significantly from the nuclear-family model. Ostriches have a mating system that has been described as SEMIPROMISCUOUS MONOGAMY. Male and female Ostriches form a type of pair-bond with each other that one biologist describes as a sort of “open marriage,” since both partners also copulate with a number of other birds besides their primary partner (birds often mate with a different primary partner each year as well). In addition, females often lay eggs in nests other than their own, especially if they are not the primary partner of a male. As a result, many of the eggs that a pair incubates (and the young they raise) are not necessarily their own. Adoption also occurs when broods are combined to form nursery groups or CRÈCHES—sometimes containing hundreds of chicks—that are looked after by one or more adults. Emus utilize SERIAL POLYANDRY in their mating system: a male pairs with one female who remains with him until incubation begins, at which point the female leaves her partner and pairs with a new male to begin a second clutch. Many females also seek nonmonogamous matings, copulating with males other than their pair-mate. One study found that the majority of copulations—nearly three-quarters—are promiscuous. In addition, copulation between pair members may be nonprocreative, occurring several months before egg laying. Greater Rheas have a variable mating system that can be characterized as SERIAL POLYGYNANDRY: a male associates with a “harem” of three to ten females, all of whom he mates with. The females lay their eggs communally in one nest; after the male begins to incubate, the females then move on to another male, repeating the process with up to seven different males. As noted above, most Emu and Rhea males are single parents, which can be an arduous task. While tending the eggs, male Rheas rarely leave the nest for more than a few minutes during the six-week incubation period. Male Emus often become severely emaciated and weakened from not eating, drinking, defecating, or leaving the nest during their entire eight-week incubation period. Nonbreeding and failed breeding attempts also occur at high rates among Greater Rheas: less than 20 percent of males even try to reproduce each year, and overall only 5–6 percent of males are successful at breeding each year.

As discussed above, sex-segregated flocks are common among Ostriches, many of whom are not involved in heterosexual pursuits. Also, heterosexual courtship is often not synchronized: females typically begin approaching males several weeks before the latter become sexually interested, and during this time the males often appear to ignore or be indifferent to the females’ advances. The onset of the males’ sexual cycle is marked by a red flush on the legs and face, as well as enlargement and erection of the penis, which is often displayed in a special “penis-swinging” ceremony. However, once males begin courting, nearly a third of their advances are, in turn, refused by females. Among Emus and Rheas, outright hostility often develops between the sexes once the male starts incubating. Fathers typically threaten, chase, or attack females that try to approach them, while female Emus have been seen responding with vicious double-footed kicks that can tumble males head over heels. Infanticide also sometimes occurs: females that are able to get close to a male tending his chicks may end up killing the youngsters. Egg abandonment or destruction takes place among Ostriches, often of eggs laid by another female. Abandonment also occurs in Greater Rheas, where nearly two-thirds of nests are deserted by males during incubation. In addition, female Rheas who are unable to find a nest and male caretaker for their eggs often lay them in the open and then abandon them; these are known as ORPHAN EGGS. Once (nonorphan) eggs hatch, fathers often adopt youngsters from other broods, raising them alongside their own. Nearly a quarter of male Rheas are adoptive parents, and up to 37 percent of each of their broods may be composed of foster chicks. Researchers have found that adopted young actually have a better chance of surviving than do their stepsiblings.

*asterisked references discuss homosexuality/transgender

Bertram, B. C. (1992) The Ostrich Communal Nesting System. Princeton: Princeton University Press.

Brown, J. L. (1987) Helping and Communal Breeding in Birds: Ecology and Evolution. Princeton: Princeton University Press.

Bruning, D. F. (1974) “Social Structure and Reproductive Behavior in the Greater Rhea.” Living Bird 13:251—94.

Coddington, C. L., and A. Cockburn (1995) “The Mating System of Free-Living Emus.” Australian Journal of Zoology 43:365—72.

Codenotti, T. L., and F. Alvarez (1998) “Adoption of Unrelated Young by Greater Rheas.” Journal of Field Ornithology 69:58—65.

———(1997) “Cooperative Breeding Between Males in the Greater Rhea Rhea americana.” Ibis 139:568—71.

*Curry, P. J. (1979) “The Young Emu and Its Family Life in Captivity.” Master’s thesis, University of Melbourne.

Fernández, G. J., and J. C. Reboreda (1998) “Effects of Clutch Size and Timing of Breeding on Reproductive Success of Greater Rheas.” Auk 115:340—48.

*———(1995) “Adjacent Nesting and Egg Stealing Between Males of the Greater Rhea Rhea americana.” Journal of Avian Biology 26:321—24.

Fleay, D. (1936) “Nesting of the Emu.” Emu 35:202—10.

Folch, A. (1992) “Order Struthioniformes.” In J. del Hoyo, A. Elliott, and J. Sargatal, eds., Handbook of the Birds of the World, vol. 1: Ostrich to Ducks, pp. 76—110. Barcelona: Lynx Edici6ns.

*Gaukrodger, D. W. (1925) “The Emu at Home.” Emu 25:53—57.

*Heinroth, O. (1927) “Berichtigung zu ‘Die Begattung des Emus (Dromaeus novae-hollandiae)’ [Correction to ‘Mating Behavior of Emus’].” Ornithologische Monatsberichte 35:117—18.

*———(1924) “Die Begattung des Emus, Dromaeus novae-hollandiae [Mating Behavior of Emus].” Ornithologische Monatsberichte 32:29—30.

*Hiramatsu, H., K. Tasaka, S. Shichiri, and F. Hashizaki (1991) “A Case of Masculinization in a Female Ostrich.” Journal of Japanese Association of Zoological Gardens and Aquariums 33:81—84.

Navarro, J. L., M. B. Martella, and M. B. Cabrera (1998) “Fertility of Greater Rhea Orphan Eggs: Conservation and Management Implications.” Journal of Field Ornithology 69:117—20.

O’Brien, R. M. (1990) “Emu, Dromaius novaehollandiae.” In S. Marchant and P. J. Higgins, eds., Handbook of Australian, New Zealand, and Antarctic Birds, vol. 1, part A, pp. 47—58. Melbourne: Oxford University Press.

Raikow, R. J. (1968) “Sexual and Agonistic Behavior of the Common Rhea.” Wilson Bulletin 81:196—206.

*Sauer, E. G. F. (1972) “Aberrant Sexual Behavior in the South African Ostrich.” Auk 89:717—37.

Sauer, E. G. F., and E. M. Sauer (1966) “The Behavior and Ecology of the South African Ostrich.” Living Bird 5:45—75.

Humboldt Penguins form mated pairs during the breeding season and nest in small colonies; they travel and feed at sea in social groups of 10–60 birds. King Penguins are highly gregarious, breeding in enormous colonies—some numbering 300,000 pairs—and generally form monogamous pair-bonds. Gentoo Penguins have a similar social system, although their nesting colonies are not as large.

Behavioral Expression: Lifelong homosexual pair-bonds sometimes develop between male Humboldt Penguins. Like heterosexual pairs, same-sex partners remain together for many years: some male couples have stayed together for up to six years, until the death of one of the partners. Same-sex pairs (like opposite-sex pairs) spend much of their time close together, often touching. They also usually live together in a nest that they have built—either an underground burrow, a shallow bowl dug in the ground, or a rock niche lined with twigs. Unlike male pairs in other birds, though, homosexual pairs of Humboldt Penguins never acquire any eggs. Courtship and pair-bonding activities are also a prominent aspect of homosexual partnerships. This includes the ECSTATIC DISPLAY, in which a male stretches his head and neck upward, spreading his flippers wide and flapping them while emitting several long, very loud donkeylike brays. Sometimes this is performed mutually by both males standing side by side. Homosexual partners also ALLO-PREEN each other, affectionately running their bills through one another’s feathers. Occasional same-sex BOWING also occurs, in which one male points his beak down toward his partner and vibrates his head from side to side. As a prelude to copulation, one male approaches the other from behind, pressing against his body and vibrating his flippers against his partner; this distinctive display is known as the ARMS ACT. Homosexual copulation occurs when the bird in front lies down on his chest, allowing the other male to climb onto his back; genital contact may occur when the male being mounted holds his tail up or to the side and exposes his cloaca. Homosexual mountings are sometimes briefer than heterosexual ones, but often the two males take turns mounting each other. Not all same-sex courtship and sexual activity occurs between birds in homosexual pairs. Males who are paired to females also sometimes court and copulate with other heterosexually paired males (as well as with females other than their own mate).

In King Penguins, same-sex pairs also occur, in both males and females. These bonds are probably not as long-lasting as homosexual pairs in Humboldts, since same-sex partners sometimes divorce each other after being together for only one season (which also occurs commonly in heterosexual pairs in this species). Courtship activities are a part of King Penguin homosexual pair-bonds, especially between males. One such display is BOWING, in which one bird approaches the other while making courtly bows, often leading to mutual bowing. Another display is DABBLING, in which the birds face each other while rapidly clapping their bills and gently nibbling or preening one another’s feathers, sometimes accompanied by quivering of the flippers and tail. This may lead to homosexual copulation, in which one bird urges the other to lie down by pressing on its back, then mounts; this occurs among both males and females. In addition, female pairs sometimes lay an (infertile) egg, which they take turns incubating.

Homosexual courtship also occurs early in the breeding season among Gentoo Penguins. A male or a female brings an “offering” of pebbles or grass and lays it at the feet of another bird of the same sex, bowing and making slight hissing noises. The other bird, if interested, may respond with bowing or arranging the material into a nest. Females that pair with each other usually lay eggs in the nest that they tend together; because these birds do not typically mate with males, their eggs are infertile. However, female pairs can become successful foster parents in captivity, incubating and hatching fertile eggs when provided and successfully raising the resulting chicks.

Frequency: In some zoo populations of Humboldt Penguins, at least 5 percent of all pairs are homosexual, and 12 percent of all copulations are between males. Among paired birds, 10 percent of mountings take place in male couples, while 15 percent of promiscuous matings (between nonmates) are homosexual. Of courtship displays performed by males to birds other than their partner, about a quarter of all arms acts are homosexual, and about 2 percent of courtship bows are same-sex. In one zoo colony consisting of five King Penguins, 2 out of 10 bonds that formed among the birds over a period of nine years were homosexual. Although same-sex matings have not yet been observed in these species in the wild, homosexual courtship has been seen in wild Gentoo Penguins: in one informal survey, 3 out of 13 courtships (23 percent) by Gentoos were same-sex.

Orientation: Some male Humboldt Penguins are exclusively homosexual, remaining with their male partners for their entire lives, or else re-pairing with another male should they lose their original partner. Other males are sequentially bisexual, pairing with a male after having lost one or more previous female mates. Still other males are simultaneously bisexual, engaging in both same-sex and opposite-sex courtship and copulation. Of these, some have a primary heterosexual bond but occasionally engage in homosexual activity with another breeding male: about 47 percent of all same-sex copulations are of this type (as opposed to occurring between bonded partners). In a few cases, the opposite occurs: a male with a primary homosexual pair-bond occasionally participates in a heterosexual copulation. Among King Penguins, birds in same-sex pairs are probably exclusively homosexual for the duration of their pair-bonds (since any eggs that are laid are infertile), and birds exhibit a “preference” for same-sex mates even when unpaired birds of the opposite sex are available. Over the course of their lives, however, most such birds are sequentially bisexual, since following the breakup of a homosexual pair they may go on to form heterosexual pair-bonds and even raise a family. Most Gentoo Penguins that participate in homosexual courtship are probably bisexual, since they court both males and females, albeit with a primary heterosexual orientation (since most go on to breed with birds of the opposite sex). Females that pair with each other are exclusively homosexual for the duration of their bond (which may last for one or both birds’ lives); some females pair with a heterosexual mate after the death of their female partner.

As noted above, promiscuous matings by heterosexually paired birds are common in Humboldt Penguins: one-third to one-half of all heterosexual copulations are between nonpair members, and courtship of birds other than one’s mate is also frequent. Promiscuous courtship and copulation occur in King and Gentoo Penguins as well. Even within pairs, sexual behavior may be nonprocreative. In Humboldts, copulation occurs both early and late in the breeding season, when the chances of fertilization are low or nonexistent, while heterosexual mounts (like homosexual ones) sometimes do not include genital contact or sperm transfer (in both Humboldts and Gentoos). Female Gentoo Penguins sometimes mount their mates (REVERSE mounting), while male Gentoos occasionally masturbate by mounting and copulating with clumps of grass. Males have also been observed trying to copulate with dead Penguins.

Several other variations on the lifetime monogamous pair-bond and nuclear family also occur. About a quarter of all Humboldt male-female pairs divorce, often when the female leaves her mate for another male. Divorce also occurs in 10–50 percent of Gentoo pairs, and in some years no pairs remain together. It is especially common in King Penguins, where only about 30 percent of birds retain the same mate from one season to the next. In addition, some King Penguins abandon their mates during the breeding season, and about 6 percent of chicks are reared by single parents (either abandoned or widowed). Humboldts occasionally form trios consisting of either one male and two females or two females and one male; these make up about 5 percent of all heterosexual bonds. In King Penguins, nonbreeding females may associate with a heterosexual pair and help them raise their chick, who recognizes all three birds as its parents; single parenting is also common. Nonbreeders that aren’t part of trios also occasionally feed chicks belonging to other birds, particularly when the chicks are in CRÈCHES. These large nursery groups, sometimes containing thousands of chicks, form while the parents are away. Crèches also occur in Gentoos, where they are often attended by several adult “guardians.” During the winter, King parents are often gone for long periods on fishing trips, and chicks may not be fed for weeks or months at a time. As many as 10 percent of them perish from this prolonged fasting and starvation. Some parents abandon their chicks or eggs (especially in severe weather), and chicks may also be killed in squabbles between their parents and nonbreeding birds that are trying to “kidnap” them. King Penguins also occasionally “steal” other pairs’ eggs.

Breeding can take its toll on adults as well: male King Penguins fast for more than fifty days during courtship and incubation, losing 10–12 percent of their body weight. In addition, heterosexual copulations are sometimes harassed, with throngs of neighboring birds converging on mating pairs, attacking them and trying to interrupt the sexual activity. Many birds forgo breeding altogether: more than 40 percent of the population each year consists of nonbreeders, and birds generally do not breed every year (primarily because of the unusually long 16—month breeding cycle). Extensive nonbreeding is also a feature of Gentoo populations: up to a quarter of the adults may skip breeding each year, and more than 15 percent of birds breeding late in the season lay infertile clutches. In addition, breeding is delayed for one to two years in younger King and Gentoo Penguins, due to both physiological and social factors. Some Humboldt Penguins remain single and nonbreeding as well, although they may still engage in sexual behavior with other birds.

Reciprocal homosexual copulations—involving full genital (cloacal) contact—also occur among male Adelie Penguins (Pygoscelis adeliae) in Antarctica, accompanied by courtship displays such as DEEP BOWING and the ARMS ACT. Following ejaculation by the mounter, the mountee contracts his cloaca, perhaps facilitating movement of his partner’s semen in his genital tract and/or indicating orgasm. Some males who participate in homosexual activity also mate heterosexually.

*asterisked references discuss homosexuality/transgender

Bagshawe, T. W. (1938) “Notes on the Habits of the Gentoo and Ringed or Antarctic Penguins.” Transactions of the Zoological Society of London 24:185–306.

Bost, C. A., and P. Jouventin (1991) “The Breeding Performance of the Gentoo Penguin Pygoscelis papua at the Northern Edge of Its Range.” Ibis 133:14–25.

*Davis, L. S., F. M. Hunter, R. G. Harcourt, and S. M. Heath (1998) “Reciprocal Homosexual Mounting in Adelie Penguins Pygoscelis adeliae.” Emu 98:136–37.

*Gillespie, T. H. (1932) A Book of King Penguins. London: Herbert Jenkins Ltd.

Kojima, I. (1978) “Breeding Humboldt’s Penguins Spheniscus humboldti at Kyoto Zoo.” International Zoo Yearbook 18:53–59.

*Merritt, K., and N. E. King (1987) “Behavioral Sex Differences and Activity Patterns of Captive Humboldt Penguins.” Zoo Biology 6:129–38.

*Murphy, R. C. (1936) Oceanic Birds of South America, vol. 1, p.340. New York: American Museum of Natural History.

Olsson, O. (1996) “Seasonal Effects of Timing and Reproduction in the King Penguin: A Unique Breeding Cycle.” Journal of Avian Biology 27:7–14.

*Roberts, B. (1934) “The Breeding Behavior of Penguins, with Special Reference to Pygoscelis papua (Forster).” British Graham Land Expedition Science Report 1:195–254.

Schmidt, C. R. (1978) “Humboldt’s Penguins Spheniscus humboldti at Zurich Zoo.” International Zoo Yearbook 18:47–52.

*Scholten, C. J. (1996) Personal communication.

*———(1992) “Choice of Nest-site and Mate in Humboldt Penguins (Spheniscus humboldti)” SPN (Spheniscus Penguin Newsletter) 5:3–13.

*———(1987) “Breeding Biology of the Humboldt Penguin Spheniscus humboldti at Emmen Zoo.” International Zoo Yearbook 26:198–204.

*Stevenson, M. F. (1983) “Penguins in Captivity.” Avicultural Magazine 89:189—203 (reprinted in International Zoo News 189 [1985]:17—28).

Stonehouse, B. (1960) “The King Penguin Aptenodytes patagonica of South Georgia. 1. Breeding Behavior and Development.” Falkland Islands Dependencies Survey Scientific Reports 23:1–81.

van Zinderen Bakker, E. M., Jr. (1971) “A Behavior Analysis of the Gentoo Penguin Pygoscelis papua.” In E. M. van Zinderen Bakker Sr., J. M. Winterbottom, and R. A. Dyer, eds., Marion and Prince Edward Islands: Report on the South African Biological and Geological Expedition, pp. 251—72. Cape Town: A. A. Balkema.

Weimerskirch, H., J. C. Stahl, and P. Jouventin (1992) “The Breeding Biology and Population Dynamics of King Penguins Aptenodytes patagonica on the Crozet Islands.” Ibis 134:107–17.

*Wheater, R. J. (1976) “The Breeding of Gentoo Penguins Pygoscelis papua in Edinburgh Zoo.” International Zoo Yearbook 16:89–91.

Williams, T. D. (1996) “Mate Fidelity in Penguins.” In J. M. Black, ed., Partnerships in Birds: The Study of Monogamy, pp. 268–85. Oxford: Oxford University Press.

———(1995) The Penguins: Spheniscidae. Oxford: Oxford University Press.

Williams, T. D., and S. Rodwell (1992) “Annual Variation in Return Rate, Mate and Nest-Site Fidelity in Breeding Gentoo and Macaroni Penguins.” Condor 94:636–45.

Wilson, R. P., and M.-P. T. Wilson (1990) “Foraging Ecology of Breeding Spheniscus Penguins.” In L. S. Davis and J. T. Darby, eds., Penguin Biology, pp. 181-206. San Diego: Academic Press.

BIRDS OF PREY AND GAME BIRDS

During early spring through summer, Kestrels associate as mated pairs that each have their own territory; there is also a significant subpopulation of nonbreeding birds. Outside of the mating season, males and females are often segregated from each other and largely solitary: sometimes only one member of a pair—typically the female—migrates, though males that migrate often travel farther than females. During the winter, males and females also tend to occupy separate habitats, with males generally in more wooded areas. Griffon Vultures are much more social and tend to nest in colonies containing 15-20 pairs, sometimes as many as 50-100. As in Kestrels, mated pairs often last for many years.

Behavioral Expression: In Kestrels and Griffon Vultures, two birds of the same sex—usually males—occasionally bond with each other and become a mated pair. Male Kestrels in a homosexual pair often soar together in the early spring, performing dramatic courtship display flights that reinforce their pair-bond (these displays are also found in heterosexual pairs). One such display is the ROCKING FLIGHT, in which the two partners fly at an immense height and rock from side to side, using flicking wingbeats. Another display is the slower WINNOWING FLIGHT, in which the wings beat with shallow, almost vibrating strokes, giving the impression that only the tips are moving or “shivering.” Both displays are accompanied by distinctive calls, such as the TSIK CALL—a series of clipped notes sounding like tsick or kit—and the LAHN CALL, a sequence of high-pitched trills transcribed as quirrr-rr quirrr-rr. The two males sometimes display together, or one male might soar while the other sits on his perch. Same-sex partners also copulate with each other, making the distinctive copulation call sounding like kee-kee-kee or kik-kik-kik; homosexual mounts last for 10-15 seconds (comparable to heterosexual matings).

Male Griffon Vultures in homosexual pairs also mate with each other repeatedly beginning in December (the onset of the mating season), and such pairs may remain together for years. The two males sometimes build a nest together each year—typically a flat assemblage of sticks on a crag, two to three feet across. Like Kestrels, pairs of Griffon Vultures perform a spectacular aerial pair-bonding display called TANDEM FLYING. The two birds spiral upward to a great height on a thermal, then glide downward in a path that will bring them extremely close to each other, “riding” for a few seconds one above the other, until they separate again. Although most tandem flights are by heterosexually paired birds, Vultures of the same sex also engage in this activity.

Frequency: Homosexual pairs probably occur only occasionally in Kestrels, although no systematic study of their frequency has been undertaken. Male pairs of Griffon Vultures have not yet been fully verified in the wild; however, tandem flights between same-sex partners (both males and females) account for about 20 percent of all display flights in the wild, and some of these probably represent homosexual pairings.

Orientation: No detailed studies of the life histories of birds of prey in homosexual pairs have yet been conducted. However, at least some male Griffon Vultures in same-sex tandem flights have female mates, suggesting a possible form of bisexuality, while at least some younger females in same-sex tandems likely have no prior heterosexual experience.

In any given year, many Kestrels do not breed: about a third of all birds in some populations are unpaired, while 6-13 percent of heterosexually mated birds do not lay eggs. Male-female pairs of Griffon Vultures, too, may abstain from procreating—some pairs go for as long as eight or nine consecutive years without reproducing. Nonlaying pairs, as well as younger Griffon Vultures that have not yet begun breeding, nevertheless still engage in sexual activity, often mating with each other near the breeding colonies. Several other types of nonprocreative copulations are also prominent in these species. Both Kestrels and Griffon Vultures sometimes mate outside of the breeding season (in the autumn and winter) and during the breeding season when there is no chance of fertilization. This includes during incubation, chick-raising, or very early in the season. Outside of the breeding season, though, Griffon females may refuse to participate in copulations, attacking their male partner when he tries to mount. Kestrel males and females very often live separately during the winter (as discussed above). In addition, heterosexual mating in both species occurs at astonishingly high rates, indicating that it is not simply procreative activity: Griffon heterosexual pairs sometimes mate every half hour, while Kestrels average a copulation once every 45 minutes, or seven to eight times per day during the breeding season. Even higher rates have been recorded for some Kestrels—up to three times per hour—and it is estimated that each Kestrel pair mates as many as 230 times during the breeding season alone. Male Kestrels also sometimes court and attempt to mate with females other than their mate; they usually do not succeed, though, owing to resistance by the female and defense by her mate. Nevertheless, 5-7 percent of all broods contain chicks fathered by a bird other than its mother’s mate, and in a few cases none of the nestlings are genetically related to their caretaking father. Nonmonogamous copulations probably also occur in Griffon Vultures.

Alternative heterosexual family arrangements are widespread in Kestrels: up to 10 percent of males in some years have two female mates (they usually each have families in separate nests), while a female sometimes forms a trio with two males. Divorce is fairly common in Kestrels: about 17 percent of females and 6 percent of males change partners between breeding seasons, and sometimes a pair splits during the breeding season as well. In Griffon Vultures the divorce rate is about 5 percent. Some Kestrel males are unable to provide their mates with enough food during incubation, resulting in desertion and loss of the entire clutch (accounting for more than half of all nesting failures). Finally, cannibalism has been documented in these species: Kestrel nestlings sometimes kill and eat their siblings, while parents of both species cannibalize their own chicks on rare occasions (usually if the chick has already died).

Same-sex pairing and coparenting have been observed in other birds of prey in captivity. Female Barn Owls (Tyto alba) that are raised together occasionally bond with one another, ignoring any available males. They may even nest together, each laying a clutch of infertile eggs that they incubate side by side. Female coparents share parenting duties and can successfully raise foster young. Courtship, pair-bonding, nesting, and coparenting of foster chicks have also been documented in a pair of female Powerful Owls (Ninox strenua) from Australia. In addition, a pair of male Steller’s Sea Eagles (Haliaeetus pelagicus)—a species native to Siberia and East Asia—courted one another and built a nest together. They even incubated and hatched another eagle’s egg and successfully raised the chick together.

*asterisked references discuss homosexuality/transgender

Blanco, G., and F. Martinez (1996) “Sex Difference in Breeding Age of Griffon Vultures (Gyps fulvus).” Auk 113:247–48.

Bonin, B., and L. Strenna (1986) “The Biology of the Kestrel Falco tinnunculus in Auxois, France.” Alauda 54:241–62.

Brown, L., and D. Amadon (1968) “Gyps fulvus, Griffon Vulture.” In Eagles, Hawks, and Falcons of the World, pp. 325–28. New York: McGraw-Hill.

Cramp, S., and K. E. L. Simmons, eds. (1980) “Griffon Vulture (Gyps fulvus)” and “Kestrel (Falco tinnunculus ).” In Handbook of the Birds of Europe, the Middle East, and North Africa, vol. 2, pp. 73–81, 289–300. Oxford: Oxford University Press.

*Fleay, D. (1968) Nightwatchmen of Bush and Plain: Australian Owls and Owl-like Birds. Brisbane: Jacaranda Press.

*Heinroth, O., and M. Heinroth (1926) “Der Gansegeier (Gyps fulvus Habl.) [The Griffon Vulture].” In Die Vögel Mitteleuropas, vol. 2, pp. 66–69. Berlin and Lichterfeld: Bermühler.

*Jones, C. G. (1981) “Abnormal and Maladaptive Behavior in Captive Raptors.” In J. E. Cooper and A. G. Greenwood, eds., Recent Advances in the Study of Raptor Diseases (Proceedings of the International Symposium on Diseases of Birds of Prey, London, 1980), pp. 53–59. West Yorkshire: Chiron Publications.

Korpimaki, E. (1988) “Factors Promoting Polygyny in European Birds of Prey—A Hypothesis.” Oecologia 77:278–85.

Korpimäki, E., K. Lahti, C. A. May, D. T. Parkin, G. B. Powell, P. Tolonen, and J. H. Wetton (1996) “Copulatory Behavior and Paternity Determined by DNA Fingerprinting in Kestrels: Effects of Cyclic Food Abundance.” Animal Behavior 51:945–55.

Mendelssohn, H., and Y. Leshem (1983) “Observations on Reproduction and Growth of Old World Vultures.” In S.R. Wilbur and J. A. Jackson, eds., Vulture Biology and Management, pp. 214–41. Berkeley: University of California Press.

*Mouze, M., and C. Bagnolini (1995) “Le vol en tandem chez le vautour fauve (Gyps fulvus) [Tandem Flying in the Griffon Vulture].” Canadian Journal of Zoology 73:2144–53.

*Olsen, K. M. (1985) “Pair of Apparently Adult Male Kestrels.” British Birds 78:452–53.

Packham, C. (1985) “Bigamy by the Kestrel.” British Birds 78:194.

*Pringle, A. (1987) “Birds of Prey at Tierpark Berlin, DDR.” Avicultural Magazine 93:102–6.

Sarrazin, F., C. Bagnolini, J. L. Pinna, and E. Danchin (1996) “Breeding Biology During Establishment of a Reintroduced Griffon Vulture Gyps fulvus Population.” Ibis 138:315–25.

Stanback, M. T., and W. D. Koenig (1992) “Cannibalism in Birds.” In M. A. Elgar and B. J. Crespi, eds., Cannibalism: Ecology and Evolution Among Diverse Taxa, pp. 277–98. Oxford: Oxford University Press.

Terrasse, J. F., M. Terrasse, and Y. Boudoint (1960) “Observations sur la reproduction du vautour fauve, du percnoptère, et du gypaete barbu dans les Basses-Pyrénées [Observations on the Reproduction of the Griffon Vulture, the Egyptian Vulture, and the Bearded Vulture in the Lower Pyrenees].” Alauda 28:241–57.

Village, A. (1990) The Kestrel. London: T. and A. D. Poyser.

During the breeding season, male Ruffed and Sage Grouse display on territories—large, communal “strutting grounds” or LEKS in Sage Grouse, and individual “drumming logs” in Ruffed Grouse. Both species have a promiscuous mating system, in which birds mate with multiple partners, do not form pair-bonds, and females care for the young with no male assistance. Outside of the mating season, birds sometimes congregate in mixed-sex flocks.

Behavioral Expression: At dawn on their prairie display grounds, female Sage Grouse gather in groups of eight to ten (or sometimes more) known as CLUSTERS. Although many are there to mate with males, some females also court and mate with each other. Homosexual courtship display is similar to that used by males and is called STRUTTING. The female takes short steps forward and turns while presenting herself in a spectacular posture—long tail feathers fanned in a circle, air sacs in the breast expanded, and neck feathers erected and rustling. Unlike males, however, strutting females do not make the characteristic “plopping” sound during courtship, owing to the smaller size of their air sacs. When the female has finished her strut, another female may solicit a copulation from her by crouching down, arching her wings and fanning the wing feathers on the ground. The other female mounts her and often performs a complete mating sequence, spreading her wings on either side of the mounted female for balance, treading on her back with her feet, and lowering and rotating the tail for cloacal (genital) contact. Some females also chase others in the group and try to mount them, and “pile-ups” of three or four females all mounted on each other sometimes develop. During most lesbian matings, males pay no attention to the females. Sometimes, however, they try to disrupt a lesbian mounting, or they may even try to join in by mounting a female who is herself mounted on another female. In one case, a male even mounted another male who was himself mounted on two females that were mounting each other! Later in the breeding season, two females also sometimes jointly parent their offspring, combining all their chicks into a single brood that they both look after.

Male Ruffed Grouse also court and mount each other. Deep in the forest, each male advertises his presence by DRUMMING at dawn or dusk, producing a throbbing, drumroll-like sound by rapidly “beating” the air with his wings. If another Grouse lands on the drumming log, he begins his strutting display. Fanning his tail like a turkey, he lowers his wings, erects his neck ruffs, and rotates his head vigorously, all the while emitting a hissing sound as he approaches the other bird. If the other bird is a female, mating takes place, whereas if it is another male, typically a fight will ensue. However, in some cases the other male does not challenge the displaying male. The courting male then makes a “gentle” approach, sleeking down his feathers, dragging his tail on the ground, and occasionally shaking his head. He sometimes pecks softly at the base of the other male’s bill or places his foot on the other’s back and may mount him as in heterosexual copulation (although the mounted bird does not usually adopt the female’s typical copulatory posture).

Frequency: Approximately 2-3 percent of Sage Grouse females participate in homosexual courtships and copulations, which occur in perhaps one out of five female visits to the lek (on average); the prevalence of homosexual behavior in wild Ruffed Grouse is not known.

Orientation: Some female Sage Grouse that mate with females do not apparently engage in heterosexual copulation; others alternate between homosexual and heterosexual activity (sometimes within a few hours or minutes). As described above, bisexual “pile-ups” involving birds of the same and opposite sexes mounting each other simultaneously also occur. In Ruffed Grouse, little is known about homosexual activity in the wild, but it is likely that there is a similar combination of bisexuality with occasional exclusive homosexuality. Displaying males that mount other males probably also court and mate with females, while those males who approach displaying males are most likely nondrumming “alternate” males (see below) that do not mate heterosexually.

In both of these species, significant portions of the population are nonbreeding. As many as 30 percent of male Ruffed Grouse are nondrummers who do not mate heterosexually, and some birds never breed during their entire lives. In fact, one researcher found that nonbreeders live longer and have a better survival rate than breeders. Many nonbreeders are younger males who have yet to acquire a drumming log; others are ALTERNATE males that tend to associate with another male on his display site without themselves drumming. Still others give up or “abdicate” their display territories and become nonbreeders. Up to 25 percent of female Ruffed Grouse may not nest in any given year, as is true for 20-32 percent of female Sage Grouse in some populations. Moreover, 14-16 percent of female Sage Grouse abandon their nests (especially if they have been disturbed), which means that any eggs or chicks they have will not survive; this also occasionally occurs in Ruffed Grouse. The majority of Sage Grouse copulations are performed by only a small fraction of the male population, and one-half to two-thirds of males never mate at all; during each breeding season, 3-6 percent of females do not ovulate either.

Even among birds that do mate, heterosexual copulation is often complicated by a host of factors: female Sage Grouse may refuse to be mounted, males often ignore females’ solicitations to mate (especially later in the breeding season), and 10–18 percent of copulations are disrupted by neighboring males who attack mating birds. In addition, males and females are often physically separated from each other: in both species, typically the only contact the two sexes have with each other during the breeding season is mating. Since each female usually copulates only once, hers is a largely male-free existence. Even on the display grounds, Sage Grouse are typically sex-segregated when not actually mating. Several types of alternative sexual behavior also occur in these species. Male Sage Grouse often “masturbate” by mounting a pile of dirt or a dunghill and performing all the motions of a full copulation. Both male Ruffed and Sage Grouse occasionally court and mate with females of other grouse species. And male Sage Grouse sometimes mount females without attempting to inseminate them (no genital contact). Moreover, even though most females mate only once (that is, the minimum required to fertilize their eggs), multiple copulations also occasionally occur: one female, for example, was mounted more than 22 times in one hour. Female Sage Grouse sometimes combine their youngsters into what is known as a GANG BROOD, a communal “nursery flock” of sorts.

Homosexual activity occurs in several species of pigeons. Feral Rock Doves (Columba livia), for example, form both male and female same-sex pairs that engage in a full suite of courtship, pair-bonding, sexual, and nesting activities. Homosexual pairs of female Ring Doves (Streptopelia risoria) in captivity are generally more devoted incubators than heterosexual pairs, being less likely to abandon their eggs.

*asterisked references discuss homosexuality/transgender

*Allen, A. A. (1934) “Sex Rhythm in the Ruffed Grouse (Bonasa umbellus Linn.) and Other Birds.” Auk 51:180-99.

*Allen, T. O., and C. J. Erickson (1982) “Social Aspects of the Termination of Incubation Behavior in the Ring Dove (Streptopelia risoria).” Animal Behavior 30:345-51.

Bergerud, A. T., and M. W. Gratson (1988) “Survival and Breeding Strategies of Grouse.” In A. T. Bergerud and M. W. Gratson, eds., Adaptive Strategies and Population Ecology of Northern Grouse, pp. 473-577. Minneapolis: University of Minnesota Press.

*Brackbill, H. (1941) “Possible Homosexual Mating of the Rock Dove.” Auk 58:581.

*Gibson, R. M., and J. W. Bradbury (1986) “Male and Female Mating Strategies on Sage Grouse Leks.” In D. 1. Rubenstein and R. W. Wrangham, eds., Ecological Aspects of Social Evolution, pp. 379-98. Princeton: Princeton University Press.

Gullion, G. W. (1981) “Non-Drumming Males in a Ruffed Grouse Population.” Wilson Bulletin 93:372-82.

———(1967) “Selection and Use of Drumming Sites by Male Ruffed Grouse.” Auk 84:87-112.

Hartzler, J. E. (1972) “An Analysis of Sage Grouse Lek Behavior.” Ph.D. thesis, University of Montana.

Hartzler, J. E., and D. A. Jenni (1988) “Mate Choice by Female Sage Grouse.” In A. T. Bergerud and M. W. Gratson, eds., Adaptive Strategies and Population Ecology of Northern Grouse, pp. 240-69. Minneapolis: University of Minnesota Press.

Johnsgard, P. A. (1989) “Courtship and Mating.” In S. Atwater and J. Schnell, eds., Ruffed Grouse, pp. 112–17. Harrisburg, Pa.: Stackpole Books.

*Johnston, R. F., and M. Janiga (1995) Feral Pigeons. New York: Oxford University Press.

Lumsden, H. G. (1968) “The Displays of the Sage Grouse.” Ontario Department of Lands and Forests Research Report (Wildlife) 83:1-94.

*Patterson, R. L. (1952) The Sage Grouse in Wyoming. Denver: Sage Books.

Schroeder, M. A. (1997) “Unusually High Reproductive Effort by Sage Grouse in a Fragmented Habitat in North-Central Washington.” Condor 99:933-41.

*Scott, J. W. (1942) “Mating Behavior of the Sage Grouse.” Auk 59:477-98.

Simon, J. R. (1940) “Mating Performance of the Sage Grouse.” Auk 57:467-71.

Wallestad, R. (1975) Life History and Habitat Requirements of Sage Grouse in Central Montana. Helena: Montana Department of Fish and Game.

*Wiley, R. H. (1973) “Territoriality and Non-Random Mating in Sage Grouse, Centrocercus urophasianus.” Animal Behavior Monographs 6:87-169.

HUMMINGBIRDS, WOODPECKERS, AND OTHERS

Long-tailed Hermit Hummingbirds form singing assemblies or LEKS composed of about a dozen males and have a polygamous or promiscuous mating system (in which birds mate with multiple partners). Anna’s Hummingbirds are not particularly social: each bird defends its own territory and does not generally associate with others. No pair formation occurs as part of the mating system; instead, males and probably also females mate with several different partners.

Behavioral Expression: Male Long-tailed Hermit Hummingbirds gather on their leks or courtship display territories in dense, stream-side thickets, singing to advertise their presence and attract birds to mate with. Their monotonous songs consist of single notes of various types—sometimes transliterated as kaching, churk, shree, or chrrik—repeated for up to 30 minutes at a time. Females and males visit the leks, and both sexes may be courted and mounted by the territorial males. In a typical homosexual encounter, a male approaches another male that has landed on his territory and performs an aerial maneuver known as the FLOAT. In this display, he slowly flies back and forth in front of the perched male, pivoting his body from side to side. Often he holds his bill wide open, exposing his bright orange mouth lining and striking facial stripes, which combine to produce an arresting visual pattern. The perched bird may respond by gaping his own bill and “tracking” the movements of the swiveling and hovering male in front of him, always keeping his bill pointed toward him. The courting male then circles behind the other male and copulates with him: he alights on the other male’s back, quivering his wings while twisting and vibrating his tail to achieve cloacal (genital) contact. Homosexual copulations are generally somewhat briefer than the three-to-five-second duration of heterosexual matings, and the mountee may fail to cooperate (for example by not twisting his own tail to facilitate genital contact).

Male Anna’s Hummingbirds also court and mount both females and males (including juvenile males). These birds usually visit the male’s territory to feed on his supply of nectar-rich currant and gooseberry blossoms. If a visiting male lands on a perch, the territorial male usually performs a spectacular DIVE DISPLAY toward him. He first hovers above the other male and utters a few bzz notes, then climbs nearly vertically in a wavering path of 150 feet or more, peering down at the other male. At the top of his climb, he suddenly dives downward at immense speed, making a shrill, metallic popping or squeaking sound just as he swoops over the other male. He then repeats the entire performance several more times. The startlingly loud sound at the end of his dives is produced by air rushing through his tail feathers and is often preceded by vocalizations such as various trilled or buzzing notes. A dive-bombing male actually orients his acrobatic display precisely to face the sun, dazzling the object of his attentions with the shimmering, iridescent, rose-colored feathers of his crown and throat. On cloudy days, he rarely performs such dives since the mesmerizing visual effect cannot be achieved. After a dive display the other male usually flies off—with the territorial male in close pursuit—and seeks refuge by perching in a low clump of vegetation away from the territory. The pursuing male sings intensely at him, uttering a loud and complex sequence of notes that sounds like bzz-bzz-bzz chur-zwEE dzi! dzi! bzz-bzz-bzz. He may also perform a SHUTTLE DISPLAY (similar to the Long-tailed Hermit’s float), flying back and forth above the other male, tracing a series of arcs with his body. A homosexual copulation attempt may then follow, with the male landing on the other’s back as in a heterosexual mount. If the mounted male tries to get away, the pursuing male may knock him down, grappling and tumbling with him while emitting low-pitched, gurgling brrrt notes (similar aggressive interactions are also characteristic of heterosexual mating attempts; see below).

Frequency: Although homosexual copulations are not frequent in these species, neither are heterosexual ones, and a relatively high proportion of sexual activity—up to 25 percent—actually occurs between males. During several extensive studies, two out of eight observed copulations in Long-tailed Hermits were between males, while one out of four sexual encounters in Anna’s Hummingbirds (where the sexes of the birds could reliably be determined) was homosexual. Moreover, when male Anna’s Hummingbirds are presented with stuffed birds of both sexes, they court and mount the males as frequently as they do the females.

Orientation: In Long-tailed Hermit Hummingbirds, approximately 7 percent of territorial males and 11 percent of all males participate in homosexual activity. Territorial males in both of these hummingbird species are probably bisexual, pursuing, courting, and mounting both females and males. Some of the male Long-tailed Hermits who visit other males’ territories are nonbreeders (they do not have their own territories), which means they probably do not participate in any heterosexual activity (at least for the duration of that breeding season). Male Anna’s Hummingbirds usually strongly resist being mounted by other males, perhaps indicating a more heterosexual orientation on their part (although females also sometimes resist heterosexual mating attempts).

Heterosexual mating in Anna’s Hummingbirds can have all of the aggressive and even violent characteristics described above for homosexual matings—males pursue females in high-speed chases and sometimes even strike them in midair, forcing them down in order to copulate. Some matings are also nonreproductive since they take place outside of the breeding season. Males in this species have their own distinct seasonal sexual cycle, with their sperm production and hormone levels greatly reduced from July through November. Male Anna’s Hummingbirds also frequently court females of other species such as the Allen hummingbird (Selas-phorus sasin) and Costa’s hummingbird (Calypte costae). Among Long-tailed Hermit Hummingbirds (as well as other species of hermit hummingbirds), males often “masturbate” by mounting and copulating with small, inanimate objects (including leaves suspended in spiderwebs).

Other than when mating, however, males and females in both of these species rarely meet. In Anna’s Hummingbirds, the two sexes occupy distinct habitats during the breeding season—males frequent open areas such as hill slopes or the sides of canyons, females occupy more covered, forested areas. Each female Long-tailed Hermit usually encounters males only once every two to four weeks when she visits the lekking areas prior to nesting. Males of both species take no part in nesting or raising of young. In addition, a significant number of birds are nonbreeders: nearly a quarter of all Long-tailed Hermit males are nonterritorial and therefore do not participate in heterosexual courtship or copulation, while of those who hold territories, only some get to mate with females.

*asterisked references discuss homosexuality/transgender

Gohier, F., and N. Simmons-Christie (1986) “Portrait of Anna’s Hummingbird.” Animal Kingdom 89:30–33.

Hamilton, W. J., III (1965) “Sun-Oriented Display of the Anna’s Hummingbird.” Wilson Bulletin 77:38–44.

*Johnsgard, P. A. (1997) “Long-tailed Hermit” and “Anna Hummingbird.” In The Hummingbirds of North America, 2nd ed., pp. 65–69, 195–99. Washington, D.C.: Smithsonian Institution Press.

Ortiz-Crespo, F. I. (1972) “A New Method to Separate Immature and Adult Hummingbirds.” Auk 89:851–57.

Russell, S. M. (1996) “Anna’s Hummingbird (Calypte anna).” In A. Poole and F. Gill, eds., The Birds of North America: Life Histories for the 21st Century, no. 226. Philadelphia: Academy of Natural Sciences; Washington, D.C.: American Ornithologists’ Union.

Snow, B. K. (1974) “Lek Behavior and Breeding of Guy’s Hermit Hummingbird Phaethornis guy.” Ibis 116:278–97.

———(1973) “The Behavior and Ecology of Hermit Hummingbirds in the Kanaku Mountains, Guyana.” Wilson Bulletin 85:163–77.

Stiles, F. G. (1983) “Phaethornis superciliosus.” In D. H. Janzen, ed., Costa Rican Natural History, pp. 597–599. Chicago: University of Chicago Press.

*———(1982) “Aggressive and Courtship Displays of the Male Anna’s Hummingbird.” Condor 84:208–25.

*Stiles, E G., and L. L. Wolf (1979) Ecology and Evolution of Lek Mating Behavior in the Long-tailed Hermit Hummingbird. Ornithological Monographs no. 27. Washington, D.C.: American Ornithologists’ Union.

Tyrell, E. Q., and R. A. Tyrell (1985) Hummingbirds: Their Life and Behavior. New York: Crown Publishers.

Wells, S., and L. F. Baptista (1979) “Displays and Morphology of an Anna X Allen Hummingbird Hybrid.” Wilson Bulletin 91:524–32.

Wells, S., L. E Baptista, S. F. Bailey, and H. M. Horblit (1996) “Age and Sex Determination in Anna’s Hummingbird by Means of Tail Pattern.” Western Birds 27:204–6.

Wells, S., R. A. Bradley, and L. E Baptista (1978) “Hybridization in Calypte Hummingbirds.” Auk 95:537–49.

Williamson, E S. L. (1956) “The Molt and Testis Cycle of the Anna Hummingbird.” Condor 58:342–66.

Acorn Woodpeckers have an extraordinarily varied and complex social organization. In many populations, birds live in communal family groups containing up to 15 individuals—typically there are as many as 4 breeding males and 3 breeding females in such groups (though nonbreeding groups also occur—see below). The remaining birds in a group are nonbreeding “helpers” that may share in the parenting duties. Within groups, the mating system is known as POLYGYNANDRY, that is, each male mates and bonds with several females and vice versa. In other populations, monogamous pairs as well as other variations on polygamy occur. Little is known about the social organization of Black-rumped Flamebacks, although it is thought that they form monogamous mated pairs.

Behavioral Expression: Male Black-rumped Flamebacks sometimes copulate with each other. One male mounts the back of the other (as in heterosexual mating), bending his tail down and thrusting it under the belly of the other male to make cloacal (genital) contact. Reciprocal mounting may occur, in which a male copulates with a male that has just mounted him. A bird involved in same-sex mounting activity may adopt a distinctive posture, in which his body is perpendicular to the branch he is perching on and his wing tips are arched toward the ground and hanging below his feet. Males also sometimes drum against a tree trunk prior to homosexual mounting.

Acorn Woodpeckers participate in a fascinating group display that involves ritualized sexual and courtship behavior, including homosexual mounting. At dusk, the members of a group gather together prior to roosting in their tree holes. As more and more birds arrive, they begin mounting each other in all combinations—males mount females and other males, females mount males and other females, young Woodpeckers mount older ones and vice versa. The mounting behavior resembles heterosexual mating, except it is usually briefer and cloacal contact is generally not involved (although genital contact does sometimes occur). Reciprocal mountings are common, and sometimes two Woodpeckers will try to mount the same bird simultaneously. Following the display, group members fly off to their roost holes to sleep. Ritualized mounting may also occur at dawn when the birds emerge from their roost holes. Because many group members are related to each other, at least some of this mounting is incestuous. Female Acorn Woodpeckers often coparent together, both laying eggs in the same nest cavity. Such “joint nesters” are often related (mother and daughter, or sisters), but sometimes two unrelated females nest and parent together as well. Joint-nesting females may continue to associate even if they happen not to breed in a particular year.

Frequency: Homosexual behavior in Black-rumped Flamebacks probably occurs only occasionally; however, heterosexual mating has never been observed in this species in the wild, so much remains to be learned about the behavior of this Woodpecker. The mounting display of Acorn Woodpeckers—including homosexual mounting—is a regular feature of the social life of this species at all times of the year, occurring daily in most groups. More than a third of all female Acorn Woodpeckers nest jointly, and about a quarter of all groups have joint-nesting females; 14 percent of these joint nests involve unrelated females as coparents.

Orientation: To the extent that they mount both males and females in the group display, Acorn Woodpeckers are bisexual (although it must be remembered that such mounting is often ritualized, i.e., it may not always involve genital contact). Not enough is known about the life histories of individual Black-rumped Flamebacks to make any generalizations about their sexual orientation.

As described above, Acorn Woodpeckers have an unusual communal family organization that can involve different forms of polygamy. In addition, many birds are nonbreeding: more than a third of all groups may not reproduce in a given year, and one-quarter to one-half of all adult birds do not procreate. In some populations the proportion of nonbreeders may be as high as 85 percent. Many of these are birds who remain with their family group for several years after they become sexually mature, helping their parents raise young; some delay reproducing for three or four years. Other nonbreeders (as many as one-quarter) do not in any way help to raise young. Some groups are nonreproductive because all their adult members are of the same sex: nearly 15 percent of nonbreeding groups have no adult females and nearly 4 percent have no adult males. In addition to the nonprocreative heterosexual behaviors mentioned above (REVERSE mounting, group sexual activity, mounting without genital contact), female Acorn Woodpeckers also sometimes copulate with more than one male in quick succession. About 3 percent of families contain offspring that result from promiscuous matings with males outside the group. Incestuous heterosexual matings occasionally occur as well, although they seem to be avoided—in fact, incest avoidance may lead to a group’s forgoing breeding for an extended time. Parenting in this species is notable for a variety of counterreproductive and violent behaviors. Egg destruction is common—particularly among joint-nesting females, who often break (and eat) each other’s and their own eggs until they begin laying synchronously. Males also sometimes destroy eggs of their own group. In addition, infanticide and cannibalism occur regularly in Acorn Woodpeckers. A common pattern seems to be for a new bird in a group—often a female—to peck the nestlings to death and eat some of them in order to breed with the other adults in the group. Parents also regularly starve any chicks that hatch later than a day after the others do.

*asterisked references discuss homosexuality/transgender

*Koenig, W. D. (1995–96) Personal communication.

Koenig, W. D., and R. L. Mumme (1987) Population Ecology of the Cooperatively Breeding Acorn Woodpecker. Princeton, N.J.: Princeton University Press.

Koenig, W. D., R. L. Mumme, M. T. Stanback, and F. A. Pitelka (1995) “Patterns and Consequences of Egg Destruction Among Joint-Nesting Acorn Woodpeckers.” Animal Behavior 50:607–21.

Koenig, W. D., and P. B. Stacey (1990) “Acorn Woodpeckers: Group-Living and Food Storage Under Contrasting Ecological Conditions.” In P. B. Stacey and W. D. Koenig, eds., Cooperative Breeding in Birds: Long-Term Studies of Ecology and Behavior, pp. 415–53. Cambridge: Cambridge University Press.

Koenig, W. D., and F. A. Pitelka (1979) “Relatedness and Inbreeding Avoidance: Counterploys in the Communally Nesting Acorn Woodpecker.” Science 206:1103–5.

*MacRoberts, M. H., and B. R. MacRoberts (1976) Social Organization and Behavior of the Acorn Woodpecker in Central Coastal California. Ornithological Monographs no. 21. Washington, D.C.: American Ornithologists’ Union.

Mumme, R. L., W. D. Koenig, and F. A. Pitelka (1988) “Costs and Benefits of Joint Nesting in the Acorn Woodpecker.” American Naturalist 131:654–77.

———(1983) “Reproductive Competition in the Communal Acorn Woodpecker: Sisters Destroy Each Other’s Eggs.” Nature 306:583–84.

Mumme, R. L., W. D. Koenig, R. M. Zink, and J.A. Marten (1985) “Genetic Variation and Parentage in a California Population of Acorn Woodpeckers.” Auk 102:305–12.

*Neelakantan, K. K. (1962) “Drumming by, and an Instance of Homo-sexual Behavior in, the Lesser Gold-enbacked Woodpecker (Dinopium benghalense).” Journal of the Bombay Natural History Society 59:288–90.

Short, L.L. (1982) Woodpeckers of the World. Delaware Museum of Natural History Monograph Series no. 4. Greenville, Del.: Delaware Museum of Natural History.

———(1973) “Habits of Some Asian Woodpeckers (Aves, Pisidae).” Bulletin of the American Museum of Natural History 152:253–364.

Stacey, P. B. (1979) “Kinship, Promiscuity, and Communal Breeding in the Acorn Woodpecker.” Behavioral Ecology and Sociobiology 6:53–66.

Stacey, P. B., and T. C. Edwards, Jr. (1983) “Possible Cases of Infanticide by Immigrant Females in a Group-breeding Bird.” Auk 100:731–33.

Stacey, P. B., and W. D. Koenig (1984) “Cooperative Breeding in the Acorn Woodpecker.” Scientific American 251:114–21.

Stanback, M. T. (1994) “Dominance Within Broods of the Cooperatively Breeding Acorn Woodpecker.” Animal Behavior 47:1121–26.

*Troetschler, R. G. (1976) “Acorn Woodpecker Breeding Strategy as Affected by Starling Nest-Hole Competition.” Condor 78:151–65.

Winkler, H., D. A. Christie, and D. Nurney (1995) “Black-rumped Flameback (Dinopium benghalense).” In Woodpeckers: A Guide to the Woodpeckers of the World, pp. 375–77. Boston: Houghton Mifflin.

Pied Kingfishers sometimes gather in flocks of 80 or more birds, and outside of the mating season they associate in small groups. Breeding birds form monogamous pairs, but there is a large population of nonbreeding males as well, many of whom help heterosexual pairs raise their young. Blue-bellied Rollers live in pairs or small groups of 3-13 birds, which are probably extended families or clans; mating may occur promiscuously among several group members.

Behavioral Expression: In Pied Kingfishers, two males sometimes develop a pair-bond and may engage in homosexual mounting and copulation attempts. Homosexual mounting can also occur among males that are not bonded to each other. In all cases, homosexual activity is found among nonbreeding males, of which there are several distinct categories. Some males are HELPERS, who assist heterosexual pairs in raising their young. There are two types of such helpers: PRIMARY helpers, adult birds who help their parents; and SECONDARY helpers, who are unrelated to the pairs they help. In addition, some nonbreeding birds are nonhelpers, who do not assist heterosexual pairs at all. Homosexual pairing probably occurs mostly in the latter group, since primary helpers are devoted to assisting their parents and are also often hostile toward secondary helpers, openly attacking and fighting with them. Some homosexual behavior may also take place among secondary helpers, although this is less likely, since such males are usually preoccupied with feeding females in the pairs they assist (though their parenting duties are usually less extensive than those of primary helpers).

A remarkable form of ritualized sexual behavior occurs among Blue-bellied Rollers, and in some cases the participating birds are of the same sex. One bird mounts the other as in regular copulation, beating its wings and sometimes grabbing in its bill the neck or head feathers of its partner. The mounter lowers its tail while the mountee droops its wings and raises its tail, in some cases achieving cloacal (genital) contact. In almost three-quarters of the cases, mounting is reciprocal (the mountee becoming the mounter and vice versa); reciprocal mounting may be more common between birds of the opposite sex, however. Sometimes, mounting with exchange of positions is performed repeatedly, with as many as 28 mounts alternating between the partners in succession. This mounting behavior is often a ritualized display performed for other birds, and sometimes the tail movements and other gestures characteristic of full sexual behavior are more stylized or attenuated. Mounting may be accompanied by a number of dramatic aerial displays (often considered signs of aggression), including acrobatic chases, SOARS (rapid ascents with wings angled in a V-shape, just prior to being “caught” by a pursuing bird), and swoops (breathtaking plummets with folded wings). Birds may also utter loud, mechanical-sounding RATTLES as well as screaming RASP notes during mounting or the associated aerial displays.

Frequency: Homosexual bonding and mounting probably occur only occasionally among Pied Kingfishers. Ritual mounting behavior is common among Blue-bellied Rollers, occurring throughout the year; the exact proportion of mounting that is same-sex, however, is not known.

Orientation: In some populations of Pied Kingfishers, about 30 percent of the birds are neither breeders nor helpers, while about 18 percent are secondary helpers—these are the segments in which male homosexual activity is found, although probably only a fraction of these birds are involved. Although secondary helpers often go on to mate heterosexually, it is not known whether the same is true of nonhelpers or birds that participate in homosexual activity. However, because of the relatively short life span (one to three years) and high mortality rate of this species, it is likely that at least some males are involved in homosexual activity for most of their lives without ever mating heterosexually.

As discussed above, there is a large segment of nonbreeders in the Pied Kingfisher population: as many as 45-60 percent of males do not mate heterosexually. Remarkably, studies have shown that the reproductive systems of primary helpers are actually physiologically suppressed, since they have reduced male hormone levels, small testes, and no sperm production. Only one in three primary helpers goes on to mate after being a helper, and it is likely that some never breed for their entire lives. In contrast, secondary helpers do not have dormant reproductive systems, but are in most cases simply unable to find female mates due to the greater proportion of males in most populations. Because secondary helpers are not genetically related to the birds they assist, a large number of Pied Kingfishers are involved in “foster-parenting.”

Sexual activity between male and female Blue-bellied Rollers is notable for its nonreproductive components: it occurs at all times of the year (not just during the breeding season), and it often involves nonprocreative REVERSE mounts or mounting without genital contact. In addition, multiple copulations—far in excess of what is required for fertilization—are common. Not only do birds mount each other repeatedly in a single session (dozens of times, as mentioned above), but both males and females may copulate with many partners, sometimes several times each with up to three birds in a row.

*asterisked references discuss homosexuality/transgender

Douthwaite, R. J. (1978) “Breeding Biology of the Pied Kingfisher Ceryle rudis in Lake Victoria.” Journal of the East African Natural History Society 166:1–12.

Dumbacher, J. (1991) Review of Moynihan (1990). Auk 108:457–58.

Fry, C. H., and K. Fry (1992) Kingfishers, Bee-eaters, and Rollers. London: Christopher Helm.

*Moynihan, M. (1990) Social, Sexual, and Pseudosexual Behavior of the Blue-bellied Roller, Coracias cyanogaster: The Consequences of Crowding or Concentration. Smithsonian Contributions to Zoology 491. Washington, D.C.: Smithsonian Institution Press.

Reyer, H.-U. (1986) “Breeder-Helper-Interactions in the Pied Kingfisher Reflect the Costs and Benefits of Cooperative Breeding.” Behavior 82:277–303.

———(1984) “Investment and Relatedness: A Cost/Benefit Analysis of Breeding and Helping in the Pied Kingfisher (Ceryle rudis).” Animal Behavior 32:1163–78.

———(1980) “Flexible Helper Structure as an Ecological Adaptation in the Pied Kingfisher (Ceryle rudis rudis L.).” Behavioral Ecology and Sociobiology 6:219–27.

Reyer, H.-U., J. P. Dittami, and M. R. Hall (1986) “Avian Helpers at the Nest: Are They Psychologically Castrated?” Ethology 71:216–28.

Thiollay, J.-M. (1985) “Stratégies adaptatives comparées des Rolliers (Coracias sp.) sédentaires et migra-teurs dans une Savane Guinéenne [Comparative Adaptive Strategies of Sedentary and Migratory Rollers in a Guinean Savanna].” Revue d’Écologie 40:355–78.

Galahs and Peach-faced Lovebirds are gregarious birds, gathering in large flocks that can number up to several hundred in Lovebirds and up to a thousand in Galahs. They typically form mated pairs, and Peach-faced Lovebirds usually nest in colonies. In addition, there are nomadic flocks of juveniles and younger nonbreeding adult Galahs. Orange-fronted Parakeets are also highly social, traveling in groups of 12-15 birds (often composed of mated pairs) and sometimes forming flocks of 50-200. During the breeding season, pairs generally separate from the flock to nest, although they periodically recongregate in small groups.

Behavioral Expression: Galahs of both sexes form stable, long-lasting homosexual pairs that participate in courtship, sexual, and pair-bonding activities. Same-sex bonds are strong, often developing in juvenile birds and then continuing for the rest of their lives (as do most heterosexual bonds). Homosexual pairs of at least six years’ duration have been documented in captivity. If one partner dies before the other, the remaining Galah may stay single or may eventually form a homosexual (or heterosexual) partnership with another bird. Pair-bonded Galahs almost always stay close to each other (rarely more than a few inches apart), feeding and roosting together both day and night. When one bird flies to a new location, it calls after its mate to join it, using a special two-syllable warbled call that sounds like sip-sip or lik-lik. If another bird intrudes between them, both partners threaten the intruder and may force it to leave by edging it out or simultaneously stabbing their beaks at it. Pair-mates spend considerable time preening each other; this intimate behavior, sometimes known as ALLOPREENING, involves one bird lowering its head in front of the other, allowing its mate to gently nibble and run its bill through the feathers. After a short time the birds switch positions, and often this develops into a playful fencing bout, in which the birds gently clash beaks and dodge each other.

Homosexual (and heterosexual) Galah pairs also perform a number of synchronized, highly stylized displays while perching side by side or facing toward or away from each other. One of the most elegant of these is WING-STRETCHING, in which each bird simultaneously fans open one of its wings. Often, one bird fans its left wing while the other opens its right to give a strikingly symmetrical, “mirror-image” effect, while in other cases each pair member fans the same wing in a parallel, but nonsymmetrical, pattern. Other synchronized displays include HEAD-BOBBING (in which the birds dip their heads down and to the side) as well as crest-raising and feather ruffling. In addition, such activities as self-preening, feeding, and leaf- and bark-stripping can also be performed in unison by pair members—in fact, homosexual pairs synchronize their behaviors about 65 percent of the time. Galahs in same-sex pairs may also court and copulate with each other. Courtship includes a sideways shuffling movement toward the partner with crest raised and facial feathers fanned forward, followed by head-bobbing and BREAST POINTING (in which mates touch their own or their partner’s breast feathers with their beaks). Sexual activity involves one bird mounting the other and making pelvic thrusts against its mate; this may occur even when the birds are still juveniles.

Peach-faced Lovebirds also sometimes form stable homosexual pairs; as in Galahs, these are probably lifelong bonds that usually originate while the birds are still youngsters. Same-sex pairs of Lovebirds also engage in frequent mutual preening. In their courtship and sexual activity, some homosexual pairs combine elements of male and female behavior. In female pairs, for example, each partner may feed the other (a typically male activity in heterosexual pairs) or invite the other to mount (a typically female activity). Other pairs are more role-differentiated, with one bird performing the behaviors most typically associated with males while the other exhibits the patterns of a female. However, in their parenting behaviors both members of female homosexual pairs adopt typically “female” duties. After having investigated several potential nest sites, they jointly select a suitable cavity that they occupy together, and each female contributes to building the nest. In Peach-faced Lovebirds, this involves a unique method of collecting nesting material: long strips of bark, grass, or leaves are tucked directly into the birds’ back and rump feathers to be carried back to the nest. Both partners lay eggs (usually infertile) and simultaneously incubate them. In contrast, male homosexual pairs never build nests.

Both male and female homosexual pairs also occur in Orange-fronted Parakeets. Same-sex couples often sit side by side—sometimes for half an hour or more at a time—preening and nuzzling each other while fluffing their plumage. Males also sometimes engage in sexual behavior with their pair-mate: one bird mounts the other, usually preceded by a display known as FAWNING or CLAWING, in which he lifts one foot in the air and places it gently on the other male’s back or wing. Female partners often COURTSHIP-FEED each other: one bird regurgitates some food and feeds it to her mate, and the two partners interlock their bills while jerking their heads back and forth. Unlike in heterosexual pairs, either bird may feed the other. This is usually accompanied by several stylized visual and vocal displays such as head-bobbing, rubbing or kneading of the bill on the branch (often producing a distinctive popping sound), fluffing of the cheek feathers, and flashing the iris of the eyes while whistling. The two mates sometimes play-fight with one another by BILL-SPARRING, in which they grasp and tug at each other’s beak. Female pairs may also jointly prepare a nest, usually constructed in arboreal termite nests: one partner excavates the entrance tunnel (as do males in heterosexual pairs) while the other hollows out the nest chamber (as do females in heterosexual pairs). Some female couples successfully compete against heterosexual pairs for nesting sites; pair-bonded females often become powerful allies that support one another and may even come to dominate opposite-sex pairs through attacks and threat behavior.

Frequency: Homosexual bonds are common in these Parrot species. In some captive populations of Galahs, for instance, one-half to two-thirds of pair-bonds are between birds of the same sex. A study of Peach-faced Lovebirds in captivity revealed that 4 of 12 pair-bonds (33 percent) were between females; a similar study of Orange-fronted Parakeets found 5 of 9 pair-bonds (56 percent) between females. Although male homosexual pairs of Orange-fronted Parakeets have been documented in wild birds, the overall incidence of same-sex bonds in the wild is not known for any of these species. However, about 1 out of every 180 nests of wild Galahs contains a SUPERNORMAL CLUTCH of 10–11 eggs, double the number of most other nests. These are undoubtedly laid by two females, perhaps members of a homosexual pair (although they could also result from alternative heterosexual arrangements—see below).

Orientation: Among captive Galahs that form some sort of pair-bond, about 44 percent of birds only form homosexual bonds, another 44 percent only develop heterosexual pairings, while about 11 percent bond with birds of both sexes. Of the latter group, a variety of bisexualities occur, usually in the context of trios or quartets of birds. One female, for example, formed a polygamous bond with two males, then went on to develop a bond with another female while maintaining her trio bond. Another female was bonded to a male who also had another female partner; she then “divorced” him and paired with another female. One male in a homosexual pair later also developed simultaneous bonds with two females. Similar bisexual trios and quartets also occur in Orange-fronted Parakeets, and females in this species sometimes compete successfully against both males and other females for the attentions of another female. In wild Galahs (especially males), it is possible that many birds form same-sex pairings in the juvenile flocks, with some later developing opposite-sex associations as adults. In Lovebirds (as well as in Galahs and Parakeets that only form same-sex pairs), at least some birds in homosexual bonds appear to be more exclusively same-sex oriented. For instance, bonds sometimes form between females even if there are available unpaired males, and one widowed female Lovebird who lost her female partner went on to form another homosexual pairing.

Although most heterosexual bonds in Galahs are lifelong and between only two birds, several other variations occur: some birds form polygamous trios (as discussed above), while 6–10 percent of Galahs divorce their partners and seek new mates. Infidelity in the form of copulations by paired Galahs with birds other than their mate is common, especially during the incubation period. Sometimes a mated pair changes partners after their eggs have been laid, usually resulting in loss of the eggs (accounting for about 2 percent of all clutches that fail to hatch). In addition, parenting in this species is not confined to a strictly nuclear-family structure: youngsters from several different families are pooled together into a CRÈCHE or “day-care” flock as soon as they are old enough to leave the nest. This allows their parents to forage on their own (although a few tending parents are always on hand in the crèche). Youngsters spend nearly as much time in these crèches as they do being cared for solely by their parents in the nest. Sometimes two pairs share the same nest hollow, with both females laying eggs in a combined clutch.

Although divorce and alternative bonding arrangements are not as prominent among Lovebirds, there is nevertheless often considerable antagonism between the sexes in heterosexual pairs. Males tend to become sexually ready each season before females; as a result, their courtship advances are frequently ignored or rejected, and females may even respond with overt aggression. Heterosexual copulations often do not culminate in ejaculation because the female refuses to allow the male to remain mounted, walking or flying out from under him while making threatening displays at him. A similar asynchrony in male and female sexual cycles may also occur in Galahs: in some years, males become ready to mate before females, but by the time the latter are ready, the males often lose interest and many pairs end up not breeding at all. Besides pairs that do not reproduce in a particular year, there is always a sizable proportion of single birds. As many as 60 percent of the adult Galahs in foraging flocks are nonbreeding birds from the nomadic population. Sometimes a nonbreeding female associates regularly with a breeding pair, “tagging along” with the male when he leaves the nest (perhaps in the hope of pairing with him). Such birds are known as “aunts” even though they are probably not related to the birds they associate with.

When a female Lovebird does consent to mate, nonreproductive REVERSE mounts may occur: as a part of courtship, males sometimes solicit females, who briefly mount them the way a male would. Other forms of nonprocreative sexual behavior also take place. Both Lovebirds and Galahs form pair-bonds as juveniles, long before they begin to reproduce—Galahs, in fact, may commence pairing and copulation up to three years before they can breed. In addition, some of the mating activity among younger Galahs involves birds mounting and thrusting against their partner’s head rather than the genital region. Among adults, at least 12 percent of all copulations occur well before fertilization is possible (four to five weeks prior to egg laying).

Homosexual pairs occur in several Parrot species related to these, including Masked Lovebirds (Agapornis personata) and Red-faced Lovebirds (Agapornis pullaria), from Africa, and female Aztec Parakeets (Aratinga astec), from central America. Same-sex pairs (both male and female) have also been documented in numerous other species of Parrots (usually in captivity). Canary-winged Parakeets (Brotogeris versicolurus) and Rose-ringed Parakeets (Psittacula krameri) in homosexual pairs engage in frequent mutual preening and soft grasping and nibbling of each other’s beak. Female pairs of Elegant Parrots (Neophema elegans) from Australia courtship-feed and mount one another, as do male pairs of Senegal Parrots (Poicephalus senegalus) and White-fronted Amazon Parrots (Amazona albifrons). Male pairs have also been reported in Mealy Amazon Parrots (Amazona farinosa). Homosexual pairing is found as well in Ornate Lorikeets (Trichoglossus ornatus) and several other species of Lories from the islands of Southeast Asia, in which courtship-feeding and copulation are regular features of same-sex pairing. One male pair of Yellow-backed (Chattering) Lorikeets (Lorius garrulus flavopalliatus) remained together for more than 14 years.

*asterisked references discuss homosexuality/transgender

Arrowood, P. C. (1991) “Male-Male, Female-Female, and Male-Female Interactions Within Captive Canary-winged Parakeet Brotogeris v. versicolurus Flocks.” Acta XX Congressus Internationalis Ornithologici, Christchurch, New Zealand (Proceedings of the 20th International Ornithological Congress), vol. 2, pp. 666–72. Wellington, N.Z.: New Zealand Ornithological Trust Board.

*———(1988) “Duetting, Pair Bonding, and Agonistic Display in Parakeet Pairs.” Behavior 106:129–57.

*Buchanan, O. M. (1966) “Homosexual Behavior in Wild Orange-fronted Parakeets.” Condor 68:399–400.

*Callaghan, E. (1982) “Breeding the Senegal Parrot Poicephalus senegalus.” Avicultural Magazine 88:130–34.

*Clarke, P. (1982) “Breeding the Spectacled (White-fronted) Amazon Parrot Amazona albifrons nana.” Avicultural Magazine 88:71–74.

*Dilger, W. C. (1960) “The Comparative Ethology of the African Parrot Genus Agapornis.” Zeitschrift für Tierpsychologie 17:649–85.

^*Fischdick, G., V. Hahn, and K. Immelmann (1984) “Die Sozialisation beim Rosenkopfchen Agapornis roseicollis [Socialization in the Peach-faced Lovebird].” Journal für Ornithologie 125:307–19.

Forshaw, J. M. (1989) Parrots of the World. 3rd ed. London: Blandford Press.

*Goodwin, D. (1983) “Notes on Feral Rose-ringed Parakeets.” Avicultural Magazine 89:84–93.

*Hampe, H. (1940) “Beobachtungen bei Schmuck- und Feinsittichen, Neophema elegans und chrysostomus [Observations on Blue-winged and Elegant Parrots].” Journal für Ornithologie 88:587-99.

*Hardy, J. W. (1966) “Physical and Behavioral Factors in Sociality and Evolution of Certain Parrots (Aratinga).” Auk 83:66–83.

*———(1965) “Flock Social Behavior of the Orange-fronted Parakeet.” Condor 67:140–56.

*———(1963) “Epigamic and Reproductive Behavior of the Orange-fronted Parakeet.” Condor 65:169–99.

*Kavanau, J. L. (1987) Lovebirds, Cockatiels, Budgerigars: Behavior and Evolution. Los Angeles: Science Software Systems.

*Lack, D. (1940) “Courtship Feeding in Birds.” Auk 57:169–78.

*Lantermann, W. (1990) “Breeding the Mealy Amazon Parrot Amazona farinosa farinosa (Boddaert) at Oberhausen Ornithological Institute, West Germany.” Avicultural Magazine 96:126–29.

*Low, R. (1977) Lories and Lorikeets: The Brush-Tongued Parrots. London: Paul Elek.

Pidgeon, R. (1981) “Calls of the Galah Cacatua roseicapilla and Some Comparisons with Four Other Species of Australian Parrots.” Emu 81:158–68.

*Rogers, L. J., and H. McCulloch (1981) “Pair-bonding in the Galah Cacatua roseicapilla.” Bird Behavior 3:80–92.

*Rowley, I. (1990) Behavioral Ecology of the Galah Eolophus roseicapillus in the Wheatbelt of Western Australia. Chipping Norton, NSW: Surrey Beatty.