Bruce Bagemihl - Biological Exuberance

Quite clearly, sex misrecognition cannot be a widespread “cause” of homosexuality in animals. Same-sex courtship, copulation, and/or pair-bonding occur in numerous species in which males and females look very different from each other: many primates and hoofed mammals, for example, and birds as varied as Ostriches, Grouse, Black-rumped Flameback Woodpeckers, and Scottish Crossbills, to name just a few. Conversely, homosexuality is not found in many animals in which males and females are visually indistinguishable. For example, same-sex activities are not reported for any of the 31 species of North American perching birds in which younger males significantly resemble adult females, while homosexuality occurs in only a small fraction of the hundreds (if not thousands) of birds in which adult males and females are identical to each other. 78Moreover, in the majority of species where homosexuality is attributed to mistaken sex identification, only one sex is involved in homosexual activity (usually males). If the animals truly could not tell males and females apart, we would expect both sexes to participate in homosexuality at comparable rates—unless, of course, only one sex has trouble identifying the other, which seems improbable. Furthermore, in many species where homosexual interactions between adult and adolescent males are attributed to the resemblance of the younger males to females, homosexuality also occurs between adults or older males, or between females, where sex misrecognition is not likely. This is true for Blackbucks, Mountain Goats, Elephant Seals, Bishop Birds, Swallow-tailed Manakins, and Superb Lyrebirds, among others. Adult-adolescent homosexuality also occurs in many species where younger males do not resemble females, or between females (where neither partner specifically resembles a male).

In some mammals and birds where homosexuality is attributed to the resemblance between younger males and adult females (e.g., Blackbucks, Manakins, Birds of Paradise), the two sexes are not necessarily identical. Rather, older adolescent and younger adult males exhibit physical characteristics that are actually intermediate between those of adult females and adult males, and they are often recognizably male. 79Even in species where homosexuality is claimed to result from the identical appearance of males and females, there are often slight but noticeable physical differences between the sexes that may be discernible to individuals. These include body and horn size in Mountain Goats, wing length in Bishop Birds (with juvenile males distinct from adult females), iris color and other aspects of eye structure in Galahs, relative size and other body measurements in Humboldt and King Penguins, patterning of tail feathers in male and female (and between adult female and juvenile male) Superb Lyrebirds, wing and tail length (and, in some populations, wing feather notching) in Ocher-bellied Flycatchers, presence of a brown forehead patch and shorter wings in female Tree Swallows, and bill structure and tail coloration between adult female and juvenile male Anna’s Hummingbirds. 80

Are these (often subtle) differences actually perceptible to the animals themselves? Implicit in many scientists’ pronouncements of sex misrecognition is the assumption that just because males and females look alike to our eyes, they must be indistinguishable to the animals as well. Species differ widely in their visual acuity, color perception, and other sensory abilities, so each case needs to be evaluated individually before any conclusions can be made about animals’ sex recognition abilities—and this has most definitely not been systematically investigated for cases involving animal homosexuality. Nevertheless, one thing is certain: we are only beginning to understand many aspects of animal perception, including heretofore unimagined powers of visual, acoustic, and temporal recognition. Scientists recently discovered, for example, that a number of birds such as starlings, Zebra Finches, bluethroats, and Blue Tits use ultraviolet vision in distinguishing between individuals and between sexes. Birds that appear identical in ordinary light have different patterns under UV that are recognized and used by other members of their species to choose mates. Likewise, males and females of some butterfly species that are indistinguishable to us have radically different appearances in UV light. In the acoustic and temporal realms, analysis of tape recordings of Lyrebird vocal mimicry has revealed that their perception of time may be ten times greater than that of humans, giving them the extraordinary ability to imitate the calls of five different birds simultaneously. 81It is quite likely, then, that animals can perceive differences in appearance or other minute sensory cues that are distinguishable only to human measuring instruments and not to human eyes (or ears).

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! 83It 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.