Biological Exuberance: Animal Homosexuality and Natural Diversity

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.

Nonreproductive and Alternative Heterosexualities

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 CRECHES. 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.

Other Species

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).

Sources

*asterisked references discuss homosexuality/transgender

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