Biological Exuberance: Animal Homosexuality and Natural Diversity

The significance of homosexual activity is sometimes also downplayed in discussions of its prevalence or frequency. Certainly many variables must be considered when trying to quantify same-sex activity, and the task is rarely straightforward (as we saw in chapter 1). Nevertheless, in some instances homosexual frequency is interpreted or calculated so as to give the impression that same-sex activity is less common than it really is or else is de-emphasized in terms of its importance relative to other species. In Gorillas, for example, homosexual activity in females is classified as “rare” because investigators observed it “only” 10 times on eight separate days. However, these figures are incomplete unless compared with the frequency of heterosexual interactions during the same period. In fact, 98 episodes of heterosexual mating were recorded during the same period, which means that 9 percent of all sexual activity was homosexual—a significant percentage when compared to other species.⁵² Similarly, investigators studying lesbian pairs in Western Gulls state, “We have estimated female-female pairs make up only 10—15 percent of the population” (emphasis added), when in fact this is one of the higher rates recorded for homosexual pairs in any bird species (and certainly the highest rate reported at that time). Homosexual mounting in female Spotted Hyenas is claimed to be much less frequent than in other female mammals, yet no specific figures are offered; the one species that is mentioned in comparison is the Guinea Pig, a domesticated rodent that is not necessarily the best model for a wild carnivore.⁵³

It is also important to consider the behavioral type and context when evaluating frequency. Homosexual copulations in Tree Swallows, for example, have been characterized as “exceedingly rare” because they have been observed only infrequently and are much less common than heterosexual matings between pair-bonded birds. However, homosexual copulations are nonmonogamous matings (i.e., they typically involve birds that are not paired to one another and may even have heterosexual mates); it is insufficient in this case to compare the frequency rates of two different kinds of copulation (within-pair and extra-pair). In fact, the more comparable heterosexual behavior—nonmonogamous copulations involving males and females—are also “rarely” seen. Early observers considered them to be exceedingly uncommon (or nonexistent), while a later study documented only two such matings during four years of observation, and subsequent research has yielded consistently low levels of observed promiscuous (heterosexual) copulations. Yet scientists now know that such matings must be common because of the high rates of offspring resulting from them—in some populations, more than three-quarters of all nestlings (as verified by DNA testing). Thus, it is likely that the frequency of homosexual nonmonogamous matings has been similarly underestimated.⁵⁴

Many scientists, on first observing an episode of homosexual activity, are also quick to classify the behavior as an exceptional or isolated occurrence for that species. In contrast, a single observed instance of heterosexuality is routinely interpreted as representative of a recurrent behavior pattern, even though it may occur (or be observed) extremely rarely or exhibit wide variation in form or context. This sets up a double standard in assessing and interpreting the prevalence of each behavior type, especially since opposite-sex mating can be a less than ubiquitous or uniform feature of an animal’s social life (see chapter 5). It also conflicts with the patterns established for other species. In repeated instances, homosexual activity was initially recorded in only one episode, dyad, or population (and usually interpreted—or dismissed—as an isolated example), but was then confirmed by subsequent research as a regular feature of the behavioral repertoire of the species—often spanning many decades, geographic areas, and behavioral contexts. ⁵⁵ It is no longer possible to claim that homosexuality is an anomalous occurrence in a certain species simply because it has only been observed a handful of times.