Bruce Bagemihl - Biological Exuberance

Fourth, the evidence for homosexual pairing as a breeding strategy is slim. According to scientists, females bond with same-sex partners in order to raise young that result from copulation (but not pairing) with males (since two-parent care is generally required in these species). However, only a relatively small proportion of females in homosexual pairs actually mate with males and lay fertile eggs: 0–15 percent of Western Gull eggs belonging to female pairs are fertile, while only 4–30 percent of Herring Gulls’ are fertilized, indicating that few such females are actually breeding. 68Most importantly, females that could potentially benefit from same-sex pairing—were it a reproductive strategy—do not generally “avail” themselves of this option. Researchers found that unpaired Herring Gull females that copulate with males do not in fact go on to form homosexual pairs in order to raise any resulting offspring, nor do they even try to form such pairs. Likewise, Ring-billed Gull, Western Gull, and Roseate Tern mothers that have lost their male partners (and are otherwise unable to find another male) do not establish same-sex pair-bonds with available females, even though they supposedly need to find a new mate to assist them with parenting. In addition, some unpaired and homosexually paired Ring-billed females may actually lay eggs in the nests of other (heterosexual) pairs. This shows that: ( a ) single females need not seek pair-bonding (with birds of either sex) in order to have their young raised by two parents, and ( b ) at least some females in homosexual pairs lay eggs that they have no intention of caring for themselves. 69

Lastly, there is not an absolute correlation between female pairs and supernormal clutches. True, in some species most lesbian pairs lay supernormal clutches, and most supernormal clutches belong to lesbian pairs. However, in many cases female pairs lay “normal”-sized clutches (or lose eggs so they end up with regular-sized clutches), while oversized clutches also regularly result from many other factors. These include egg stealing or adoption, supernumerary clutches laid by one female, nest-sharing by two heterosexual pairs, egg laying by outside females (not paired to the nest owners), and heterosexual trios, among others. In many gulls and other species, the connection between supernormal clutches and homosexual pairs has never been established (e.g., glaucous-winged gulls) or has been refuted (e.g., black-tailed gulls, brown noddies). Hence, studies that show correlations between toxins and increases in supernormal clutches cannot reliably be extrapolated to homosexual pairing unless it has been independently established that female pairs in that species lay larger than average clutches. 70

Scientists also frequently point out a “correlation” between the two end points of this chain—toxins and supernormal clutches—without also providing evidence for all the intervening links. 71To show conclusively a relationship between the two phenomena, all the intermediate sequences need to be established, and they should preferably be established for the particular species in question . Sometimes, extrapolations are made in these links between species: that is, toxins are shown to be in the environment of one Gull species, feminization from toxins in another Gull species, skewed sex ratios in a third, female homosexual pairs in a fourth, and supernormal clutches in others—yet rarely (if ever) have all these conditions been shown to coexist in the same species or geographic area. 72Moreover, in many Gull studies this chain is collapsed entirely or rendered circular. If homosexuality occurs in a species, and there is also evidence of contamination or pollutants in the environment, the two are automatically assumed to be linked. Homosexual pairing is regarded as a self-evidently “dysfunctional” phenomenon (typically characterized as “reproductive failure”), hence investigators often feel no need to address the actual details of occurrence or causation in the supposed link to toxins. Indeed, the very existence of homosexuality is often subtly equated with environmental contamination and disease even when no actual pollutants have been discovered in the population in question. Ultimately, female pairing is seen as more than simply a behavioral response to certain demographic parameters, which may or may not be indirectly traceable to certain chemical effects. Rather, it assumes the status of a pathological “symptom” directly induced by man-made toxins, symbolizing the larger havoc that people have wreaked on the environment—nature gone awry as a result of human meddling. 73In the end, homosexuality becomes not merely the result of pollution, but the very “contamination” that is itself poisoning otherwise healthy—that is, purely heterosexual—species.

In summary, then, unavailability of the opposite sex is, at best, a tenuous “explanation” for the occurrence of animal homosexuality. Aside from having questionable theoretical and methodological underpinnings, this explanation is in many cases simply incompatible with the facts. In other cases, while same-sex activity does occur in contexts where opposite-sex partners are unavailable, many additional factors are involved, and many important questions concerning its occurrence remain to be addressed. Why, for example, do only some individuals or species with sex-skewed populations exhibit homosexual activity, while others manifest a wide variety of alternative behavioral responses? And why have social systems that entail sex segregation or skewed sex ratios—and hence that supposedly “favor” homosexual activities—evolved in the first place, and in so many species? Where it is relevant, unavailability of the opposite sex should be seen as only one of many contributing factors—and the beginning of further study of other more complex issues surrounding the occurrence of homosexuality in animals. Unfortunately, this explanation continues to be offered as a final scientific pronouncement on the “cause” of same-sex activity. Not only does this do a disservice to the actual richness of animal behavior, it effectively discourages further investigation of a phenomenon whose true intricacies are just beginning to be understood.

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. 74However, 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. 75Often, 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. 76Conversely, 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