Biological Exuberance: Animal Homosexuality and Natural Diversity

———(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 DUNNART

IDENTIFICATION: A small, mouselike marsupial with a thick, conical, fat-storing tail. DISTRIBUTION: Inland southern Australia. HABITAT: Varied, including rocky areas. STUDY AREA: University of Adelaide, Australia.

NORTHERN QUOLL

IDENTIFICATION: A catlike marsupial, up to 2 feet long, with grayish brown fur and white splotches. DISTRIBUTION: Northern and eastern Australia. HABITAT: Woodland, rocky areas. STUDY AREA: Monash University, Australia.

Social Organization

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.

Description

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.

Nonreproductive and Alternative Heterosexualities

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).

Other Species

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.

Sources

*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 fur 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.