Bruce Bagemihl - Biological Exuberance

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.

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.

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.

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.