Biological Exuberance: Animal Homosexuality and Natural Diversity

Further evidence that animals can differentiate between males and females that appear identical to us comes from the different frequencies of homosexual and heterosexual interactions in species with “indistinguishable” sexes. Animals often preferentially court, mate, or bond with individuals of one or the other sex. Male Mountain Goats. for example, court male yearlings more frequently than female yearlings even though they are supposedly “unable” to differentiate between the two. The opposite scenario occurs in Musk-oxen: although adult males court both yearling males and females, they interact with females more than with males. Likewise, Dwarf Cavy adult males court juvenile males more often than they do juvenile females (and even seek out specific male partners). In contrast, adult males in the closely related Aperea court only juvenile females and never males, even though in both of these species juvenile males and females are purportedly indistinguishable. Among Bighorn Sheep, rams are claimed to be sexually interested in other males in direct proportion to how closely the latter resemble females—yet yearling males, which resemble females the most, still receive far less sexual attention than do females, indicating that some form of sexual differentiation still occurs. Although male Common Murres are said to mount other males because they have difficulty distinguishing the sexes, females are still mounted at a much higher rate than males. Supposedly “indiscriminate” sexual chases by male Flamingos actually involve many more pursuits of females than males. Finally, adult male Pronghorns court and mount yearling and two-year-old males, both of whom superficially resemble females. However, adults actually direct more sexual behavior toward two-year-olds, who are as “femalelike” as (if not more “malelike” than) yearlings in terms of the size of their horns and black cheek patches.⁸²

A related argument against sex misrecognition as a factor in precipitating homosexuality is that males and females are often behaviorally distinct even when they are physically identical. A male who “looks like” a female will frequently perform identifiably male behavior patterns during a homosexual interaction, seriously casting doubt on the notion that his partner has failed to recognize his actual sex. Male Antbirds “mistaken” for females actually initiate and reciprocate courtship feeding with their male partners (something females never do). Younger male Swallow-tailed Manakins and Regent Bowerbirds that participate in courtship with adult males may physically resemble females, but they exhibit distinctly “masculine” behaviors, displays, or vocalizations. Among male Greenshanks, both participants in homosexual copulations display in a typically male fashion prior to same-sex mounting, and both female partners in Jackdaw homosexual pairs preen each other (a typically female activity). There is hardly a more identifiably “male” activity than copulating with a female, yet male Laughing Gulls sometimes make sexual advances toward males who are in turn mating with their female partners (creating a three-bird “pile-up”). Nor are such homosexual mounts simply attempts by the topmost male to mate with the female, since he often remains mounted on the other male (or continues to remount him repeatedly) even after the female becomes “available” once her partner dismounts. Conversely, there is hardly a more definitively “female” activity for birds than laying eggs, yet male Black-headed Gulls have been observed bypassing females in the very act of laying an egg in order to try to copulate with her male partner!⁸³ It seems highly unlikely that homosexual activity in a case such as this is due to faulty sex recognition (especially since heterosexual copulation attempts on laying or incubating females are fairly routine among Gulls), yet this is a prominent “explanation” for same-sex behavior in this species.

Deceptively Clear