Biological Exuberance: Animal Homosexuality and Natural Diversity

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 fur Saugetierkunde 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.

RUFOUS BETTONG

IDENTIFICATION: A small (6–7 pound), rodentlike kangaroo with reddish brown fur. DISTRIBUTION: Eastern and southern Australia. HABITAT: Grassy woodlands. STUDY AREAS: National Parks and Wildlife Service Center, Townsville, Australia; Zoological Garden of West Berlin, Germany.

DORIA’S, MATSCHIE’S TREE KANGAROOS

IDENTIFICATION: Stocky, tree-dwelling kangaroos; chestnut or chocolate brown fur with lighter patches. DISTRIBUTION: Interior New Guinea; Doria’s is vulnerable, Matschie’s is endangered. HABITAT: Mountainous rain forests. STUDY AREAS: Karlsruhe Zoo, Germany; Woodland Park Zoological Gardens, Seattle, Washington.

Social Organization

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.

Description

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.

Nonreproductive and Alternative Heterosexualities

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.

Other Species

Female Tasmanian Rat Kangaroos (Bettongia gaimardi) also engage in homosexual mounting.

Sources

*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.