“The Errors of Their Ways”—Homosexuality as Mistaken Sex Identification
One surprisingly common scientific “explanation” for the occurrence of animal homosexuality is that it simply results from an inability on the part of animals to “properly” differentiate males from females, or else it represents an “indiscriminate” mating urge (i.e., any perceived differences between the sexes are ignored). This explanation is common for some “lower” animals such as insects and amphibians, where there is limited evidence that mating may indeed be random between homosexual and heterosexual.74 However, this type of “indiscriminatory” mating or mistaken sex identification has also been proposed for higher animals, including more than 55 mammals and birds—mostly species in which adult males and females superficially resemble each other (e.g., Cliff Swallows), or in which adolescent or juvenile males supposedly resemble adult females (e.g., Blackbucks, Birds of Paradise).
The gist of this explanation is that when animals engage in homosexuality they are just “making a mistake”—they intend to mate heterosexually, but simply misidentify the sex of their partner because of the physical resemblance between the sexes. Indeed, homosexual interactions are explicitly labeled as “mistakes” or “errors” in several species. Male Cock-of-the-Rock who mount other males have actually been described as “confused” and “bumbling”; the “aberrant sexual behavior” of male Giraffes who mount each other is attributed to their “muddled reflexes”; Black-billed Magpies are characterized as “confused” when they engage in “misdirected” courtship activity with birds of the same sex; and one scientist even suggested that same-sex courtship in Mountain Sheep would probably never occur if males could properly distinguish females from young males.75 Often, the very existence of homosexuality in a species is taken to be “proof” that the animals cannot distinguish males from females: “In many waders the sexes are difficult to distinguish, not only to the observer, but on occasions to the birds themselves, as records of males attempting to copulate with other males have been recorded.” The circularity in this line of reasoning is blatant, since usually no further evidence is offered to indicate that sex misrecognition is prevalent in the species.76 Conversely, the absence of homosexuality in species such as yellow-eyed penguins and its infrequency in Silvery Grebes and Red-faced Lovebirds is offered by scientists as evidence that there are no “problems” with sex recognition in these species.77
Bumbling and Confused?
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.78 Moreover, 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.79 Even 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
An adult male Blackbuck courting a younger male by “presenting the throat,” a stylized courtship display. Some scientists have suggested that homosexual activity in this species is triggered by the resemblance between younger males and adult females (e.g., their lighter coat color), yet younger bucks are clearly identifiable as male because of their horns and other anatomical features.
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.81 It 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).