Biological Exuberance: Animal Homosexuality and Natural Diversity

Even same-sex activity that does have its genesis in the absence of opposite-sex partners—so called situational homosexuality—often shows remarkable longevity and durability, rarely conforming to the stereotype of being “fragile” or liable to disintegrate once heterosexual mates are available. Captive animals that bond sexually with one another when opposite-sex partners are completely unavailable often resist later attempts to “convert” them to heterosexuality. They may even exhibit a longer-term “preference” for same-sex mates that outlasts their initial “situational” introduction to homosexuality. A pair of male White-fronted Amazon Parrots, for example, vigorously refused the advances of female birds even though their homosexual bond was formed “because” no females were available, while two female Long-eared Hedgehogs who were sexually involved with each other in the absence of males refused to mate heterosexually for up to two and a half years after they were separated (as mentioned earlier). The bonding in same-sex pairs of male Steller’s Sea Eagles and female Barn Owls (housed without any heterosexual mates) was strong enough to enable successful coparenting of chicks, and in some cases the birds ignored subsequent introductions of opposite-sex partners. Male Rhesus Macaques, Crab-eating Macaques, Bottlenose Dolphins, Cheetahs, and Black-headed Gulls with homosexual bonds resist the attentions of opposite-sex partners or are clearly distressed when separated from one another, and/or they promptly renew their relationship on being reunited—often showing visible signs of affection and excitement when seeing their male partner again. This is also true for male Mallard Ducks that are raised together, in whom homosexual pairing typically becomes their lifetime “orientation.” They consistently seek the company of other males even when opposite-sex mates are available and maintain their homosexual bonds year after year (or re-pair with males after the death of a partner) in spite of persistent overtures from females.⁵⁵

The Contamination of Homosexuality

Of all the scientists who have advocated a shortage explanation for homosexuality, not one has ever specified a critical sex ratio that will consistently “induce” homosexuality, or a crucial threshold of members of the opposite sex that must be present in order to unfailingly prevent individuals from “resorting” to homosexuality. Is a mere 5 percent surplus of one sex enough to tip the scales? Apparently, since a population of Ring-billed Gulls with only 55 percent females is claimed to have enough of a skew to “cause” homosexual pairing. Yet a 5 percent excess of males in other species such as Greylag Geese is apparently not sufficient to “precipitate” homosexual pairing.⁵⁶ In fact, it is highly unlikely that a single critical sex ratio could ever be specified, because the proportion that “causes” homosexuality in one species (or population) has no such effect at all in other species, even where enormous “surpluses” (of, say, 80 percent or more of one sex) are concerned. More broadly, the underlying assumption behind the shortage hypothesis—that sex ratios actually determine a species’ mating habits and social systems—has already been shown to be false for other types of mating behaviors. Scientists now recognize that there is not a clear, one-way causal relationship between how many males or females are available in a population, and the form that their mating system takes (e.g., polygamy as opposed to monogamy). Rather, a complex interplay of many factors is at work.⁵⁷ Unfortunately, the subtlety of this interaction is generally only recognized where heterosexual mating systems are concerned.