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.

The shortage hypothesis is not only suspect on theoretical grounds, it is often applied to particular cases in a hasty or inconsistent fashion. Skewed sex ratios in animals exhibiting same-sex activity are often presumed without adequate supporting evidence, or else questionable “explanations” are proposed for the origin of such skewed ratios.⁵⁸ This is best illustrated by the species in which the shortage explanation is most prominent: Gulls. In the late 1970s and early 1980s scientists noticed that high levels of DDT and other environmental contaminants seemed to be associated with some populations of Western and Herring Gulls where nests contained supernormal clutches (often belonging to lesbian pairs). The following chain of “causation” was proposed to explain the apparent correlation: toxins (such as DDT) cause “feminization” of male Gull embryos, which in turn leads to female-biased sex ratios, which in turn results in lesbian pairs, who then attempt to breed, ultimately laying supernormal clutches.⁵⁹ Let’s set aside for the moment the fact that this explanation is only of limited applicability—homosexual pairing is not associated with environmental toxins in over 70 other bird species, including several Gulls (e.g., Ring-billed Gulls, Common Gulls, and Kittiwakes).⁶⁰ Let’s also set aside the fact that it is only of limited explanatory value—even if it could be shown conclusively that same-sex pairing results from skewed sex ratios that in turn result from toxins, the fact that only some species (and only some individuals in each species) respond to such conditions with homosexuality would still need to be addressed. Even for the Gull species where this explanation is supposedly relevant, however, each link in the overall chain is weak.

First, although laboratory experiments have shown that some toxins may cause male bird embryos to develop some ovarian tissue, no “feminized” male chicks or adults have actually been found in the wild among Western Gulls (or other species) living in contaminated areas.⁶¹ Second, it is unlikely that toxin-induced feminization of males would result in populations with more breeding females than males (since it is most definitely not the case that toxins actually “convert” male embryos into female birds with fully functional ovaries). It would have to act either directly on the health of males, causing more deaths, or indirectly, by resulting in behavioral changes in males that would prevent them from mating with females. But there is no direct evidence that toxins cause anything beyond some physiological alterations in the reproductive organs of Gulls.⁶² A higher mortality rate among males exposed to toxins has never been demonstrated, nor have behavioral differences among such males been observed that might lead them to forgo mating or otherwise to be “unavailable” as mates.⁶³ It has been suggested that “chemically sterilized” males simply fail to join the breeding colonies, or that such males are “no longer interested” in copulating heterosexually. Yet this begs the question of how or why sterility (or other physiological modifications) causes such males to exempt themselves from reproductive activities, or what exactly prevents them from pairing (or even copulating) with females even if they are sterile. Just because an animal is intersexed or transgendered (e.g., “feminized”) does not necessarily mean that it is asexual or that its reproductive organs or behavior are “dysfunctional.” “Masculinized” female Deer, Bears, and Spotted Hyenas, for example, regularly mate with males, give birth, and raise offspring—even though such individuals often have highly modified reproductive anatomies and hormonal profiles. Even when they are sterile, transgendered and intersexual animals in other species engage in courtship, copulation, and/or pair-bonding. Thus, it is overly simplistic to equate changes in reproductive physiology with an absence of sexual, pairing, or even procreative abilities. It should also be pointed out that a skewed sex ratio is not necessarily an “unnatural” result of environmental contamination: many Gull populations are in fact “naturally” biased in favor of females independently of the effects of toxins, owing to the overall higher survival rate of females (among other factors).⁶⁴

Regarding the third link in this proposed chain: skewed sex ratios do not in fact automatically result in homosexual pairs—some populations of Western and Herring Gulls with a disproportionate number of females, for example, have few (if any) same-sex pairs.⁶⁵ Even in populations that do have a surplus of females, only a subset of the birds actually form homosexual pairs: most unpaired female Herring Gulls remain single (lesbian pairs constitute less than 3 percent of all pairs, and sometimes as few as 1 in 350), and some males remain unpaired even in populations with more females than males (indicating that some “extra” females are bypassing heterosexual mates). Granted, scientists were able to “induce” the formation of female pairs in a population of Ring-billed Gulls by removing males. However, this simply demonstrates that many females in this species have a latent bisexual capacity that manifests itself when males are in short supply—not that all same-sex pairs in this (or any other species) result from a shortage of the opposite sex. Moreover, the sex ratio that was required to “trigger” homosexual pairing (77 percent females) was much higher than the proportion of females in naturally occurring populations with homosexual pairs (55 percent females).⁶⁶ Apparently not all bird species have this latent bisexual capacity either (or at least not to the same extent), since homosexual pairing does not occur in most species that have their sex ratios experimentally manipulated. Removing males (or adding females) to populations of willow ptarmigans, bufflehead ducks, Pied Flycatchers, great tits, Brown-headed Cowbirds, and song, seaside, and savanna sparrows, for example, results in females mating polygamously with males or remaining single (among other strategies) rather than forming same-sex pairs. When alternate heterosexual behaviors such as polygamy are “induced” in usually monogamous species such as these, scientists do not interpret this as evidence that the behavior is somehow “artificial” or that its occurrence is due solely to the experimentally triggered demographic changes. Rather, it is taken to indicate that the species possesses an inherent capacity for polygamy (and more broadly, a flexibility of mating behavior), perhaps expressed at relatively low levels in most populations but manifesting itself on a larger scale under the appropriate conditions.⁶⁷ Significantly, this interpretation has not generally been afforded homosexual pairing.

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.⁶⁸ Most 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.⁷¹ To 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.⁷² Moreover, 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.⁷³ In 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.

“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).

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!⁸³ It 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.

Deceptively Clear

In many animals where only a subset of the population resembles the opposite sex (or is transgendered), the occurrence of homosexuality is often directly counter to what would be expected if confusion between the sexes were “causing” homosexual behavior. For example, adolescent male Scottish Crossbills resemble females in their plumage coloration, yet homosexual pairs in this species form between adult males, not between adult and juvenile males. In Ruffs, some males resemble females in that they lack the elaborate neck feathers and other distinctive plumage characteristics of other males, yet homosexuality in this species is not limited to these “naked-nape” males. Males who do not resemble females also court and mount each other, while “femalelike” males often mount more “masculine” males. Tree Swallows are unusual among North American perching birds in that females retain the drab gray-brown plumage of adolescence during the first year that they breed, making them resemble adolescent males more than adult females. Thus, one would expect that either (a) adult males would be more apt to “mistake” brown-plumaged females for males, perhaps responding more aggressively to them (i.e., as if they were males); or (b) homosexuality in this species would manifest itself as an age-based system, with males pursuing only younger brown-plumaged males because they “mistake” them for first-year breeding females. Neither of these scenarios is true, however: males have no trouble recognizing the sex of brown-plumaged females (and in fact are significantly less aggressive toward them), and homosexuality in this species involves adult males interacting with each other, not adults being “confused” by brown-plumaged males.⁸⁴

Black-headed Gull males and females are nearly identical in appearance, except that males have, on average, slightly longer heads and bills than females. However, some males are more “femalelike” in that they have shorter head and bill lengths than average. If sex misrecognition were operative in this species, one would predict that smaller males (i.e., birds who more closely resemble females in size) would be more likely to form homosexual pairs (since males would “mistake” them for females) and less likely to form heterosexual pairs (since females would “mistake” them for other females). On the contrary, scientists studying sex recognition in this species found that female-resembling males are just as likely to form heterosexual as homosexual pair-bonds. In fact, smaller males are more successful at maintaining long-lasting heterosexual bonds and fathering chicks than more “masculine”-appearing males—paralleling other cases of greater heterosexual prowess in some transgendered animals.⁸⁵

Other species in which both transgender and homosexuality occur are particularly cogent examples of how ineffective sex misrecognition is in “explaining” homosexuality. Typically, the patterns of same-sex and opposite-sex interactions in these species do not follow the clear divisions that would be expected if individuals were simply “mistaking” their partners for the opposite sex. In Hooded Warblers, for example, some females have transvestite plumage, appearing almost identical to males because of their dark hoods (which are usually found only in males). Others have intermediate plumage, darker or more melanistic than most females but without the complete hood pattern of males, while others have no “malelike” head feathers at all. Males, though, are typically heavier and have longer wings than females, hooded or otherwise. It has been suggested that male homosexual pairs initially form in this species because of the visual resemblance between some females (transvestites) and males. Yet if males in homosexual pairs tended to confuse hooded females with males, one might expect them to pair with individuals whose sex is especially “blurred” or hard to decipher: darker, more malelike females and/or smaller, more femalelike males. However, at least one bisexual male chose just the opposite kinds of mates. His male partner did not have female body proportions but, on the contrary, was exceptionally “masculine” in this regard, exceeding the average weight and wing lengths of most males. Conversely, his heterosexual pairings involved “obviously” female partners, i.e., nontransvestite or only moderately melanistic individuals. Moreover, males that are supposedly mistaken for females in homosexual pairings do not develop brood patches (a distinctive bare patch of skin on the belly used for incubating eggs, characteristic only of females). So it is unlikely that such males are mistaken for hooded females.⁸⁶ There is also evidence that male Hooded Warblers do not generally confuse transvestite or melanistic females with males. First of all, males are differentially aggressive toward other males, attacking them during territorial encounters more often and ignoring them less often than they do the darkest, most malelike females. Furthermore, “masculine-appearing” (melanistic) females are generally as successful as nontransvestite females in finding male partners and are as subject to promiscuous copulation attempts by males as are nontransvestite females.⁸⁷ If males tended to confuse hooded females with males, they would probably avoid darker birds (including melanistic females) during heterosexual mating interactions (since such birds would more likely be other males), yet this does not appear to be the case.

Transgendered Hooded Warblers: females of this species usually have little or no black on their heads (far left), but some individuals are plumage transvestites, exhibiting a full malelike black hood and chin strap (far right). Other females exhibit a gradation of plumage patterns that fall between these two extremes (center).

Even in species where some individuals clearly are “tricked” into same-sex relations by transgendered animals, the situation is considerably more complex than this. In Common Garter Snakes, for example, some males produce a pheromone that is similar to the scent of females. These individuals are called she-males by scientists, and they attract as many male suitors as female snakes do. Most males who court she-males are apparently “deceived” into thinking they are interacting with a genetic female. However, she-males and genetic females are not identical: chemical analysis has shown that the pheromones of she-males, rather than being indistinguishable from those of females, are actually intermediate between those of males and females. When given a choice, most nontransvestite males prefer genetic females—demonstrating that they can distinguish between the two under the appropriate circumstances. Moreover, nontransvestite males sometimes abandon their courtship of females to pursue she-males, and up to 20 percent of males may actually prefer courting she-males rather than females when given a choice—indicating that not all individuals who interact with transgendered snakes do so entirely under “false pretenses.” Even though their pheromones resemble females’, she-males also have no trouble finding opposite-sex partners—in fact, some studies indicate that they may be more successful in mating with females than males who are not transvestite (she-males actually have more than three times as much testosterone as do males). In addition, male Garter Snakes also occasionally court each other in situations that do not appear to involve transvestism—and therefore not all same-sex interactions can be attributed to (transgender-induced) mistaken sex identification. In many other species where a subset of the population is transgendered, homosexuality does not occur at all, and transgendered individuals again have no difficulty in attracting mates of the opposite sex. This is true for female red-winged blackbirds that have malelike epaulets, female Pied Flycatchers that have the white forehead patches characteristic of males, female lesser kestrels that have male rump and tail coloration, and younger male long-tailed manakins whose plumage resembles that of females.⁸⁸ If sex misrecognition were a “cause” of homosexual pairing, one would expect same-sex pairing, courtship, or mounting to be prevalent in these species as a result of “confusion” between transvestite individuals and members of the opposite sex. One would also expect transvestite individuals to be avoided by members of the opposite sex because they do not resemble “obviously” heterosexual partners. Once again, neither of these scenarios generally occurs.

Another problem with attributing homosexual interactions to mistaken sex identification is that it can (at most) account for the initial interest of one animal in another of the same sex. It cannot explain why the animal “mistaken” for the opposite sex often willingly participates in the homosexual interaction or may even initiate it. Even if homosexual pairs in Antbirds, for example, result from an initial failure on the part of a courting male to distinguish between the sexes (as has been claimed), such pairs could not persist for years unless both males were actively fostering the bond between them (or at the very least, not resisting the homosexual relationship). As scientists studying homosexual matings in Tree Swallows have pointed out, even if males mistake other males for females (which is not likely), the males they copulate with nevertheless do not resist their homosexual advances and even actively facilitate genital contact. Notably, they do not adopt the specific tactics used by birds in this species to deter unwanted sexual advances (typically displayed by females in heterosexual contexts). While male Black-crowned Night Herons may court males and females indiscriminately, their male partners are nevertheless sexually stimulated by the performance and may go on to form a homosexual pair-bond with them. In Regent Bowerbirds, “female-resembling” adolescent males may actually initiate courtship display toward adult males (the reverse of the usual scenario in cases of “mistaken” sex identification). Finally, male Greenshanks who visit other males’ territories and are “mistaken” for females actively precipitate homosexual courtship pursuits: they depart from the territory using a special swerving flight pattern that invites the other male to follow them (also used by females during heterosexual courtships). If they did not want to spark a homosexual courtship, they could simply employ any of the several strategies used by females to deter males’ advances in this species, such as leaving the territory in a direct flight path or “leapfrogging” over a pursuing male during a ground chase—yet these are not typically part of homosexual interactions.⁸⁹ Thus, even if mistaken sex recognition is responsible for bringing two animals of the same sex together, it is ultimately irrelevant in explaining why those two animals often remain together to continue their interaction and bring it to its full conclusion, be it a completed courtship or mating episode, or a pair-bond lasting many years.⁹⁰

In summary, a whole host of considerations cast serious doubt on mistaken sex recognition or indiscriminate mating as an explanation with wide applicability (or credibility). Once again, the complexities of animal behavior elude the broad brushstrokes of human interpretation. Numerous interconnected elements must be factored in, such as the subtleties of actual physical differences between the sexes, the strength and acuity of animals’ various perceptual abilities, differential behaviors between males and females, the active participation of individuals “mistaken” for the opposite sex, and the intricacies that arise when transgender is layered over homosexuality. In the end, the most significant “misrecognition” is probably not that of animals who overlook each other’s sex, but that of scientists who fail to recognize the importance and interplay of these factors. Nevertheless, even if mating or courtship in some species is in fact random or indiscriminate between males and females, such “randomness” is actually compelling evidence (once again) for a bisexual capacity in such creatures. This in itself is a vital observation that is frequently downplayed by scientists, who all too readily discount the homosexual part of this mating equation as a necessary “error” made by animals on their path to achieving greater heterosexual output. In such a mechanistic view, animals simply mate with as many partners as they can—male or female—to maximize their reproductive success, even if it means that some of their matings will be nonreproductive. The fact remains, however, that such animals have the ability to respond sexually to individuals of their own sex—and they do so repeatedly, with apparent enthusiasm, and (one might add) noticeable disregard for the “mistakes” they are making.

“Gross Abnormalities of Behavior”—Homosexuality as Pathology

Homosexuality in animals has frequently been regarded as a pathological condition. Such terms as abnormal and aberrant are routinely applied to this phenomenon (as mentioned in chapter 3), often with no further justification or explication—homosexuality is considered sufficient in itself to warrant the label of disease, disorder, dysfunction, or deviance. A number of researchers, however, are more specific in their pathologizing of homosexuality and transgender, and in this section we’ll examine two of the principal “explanations” of this sort that have been put forward: the claims that homosexuality is caused by the artificial conditions of captivity, and that homosexuality/transgender is the manifestation of a physiological abnormality.

Something Amiss at the Zoos

For a long time, scientists discounted examples of animal homosexuality because some of the earliest descriptions were based on captive animals. In many cases, biologists continue to classify this behavior as “abnormal” and attribute it to the “unnatural” circumstances of confinement or contact with humans. One scientist, for example, writes of homosexual pairs in Swans (as well as other “sexual aberrations” such as heterosexual trios and interspecies matings): “Captive swans, like many other animals, sometimes show gross abnormalities of behavior. These are due almost entirely to the artificial conditions under which the birds are kept.”⁹¹ As recently as 1991, homosexuality in Wattled Starlings was ascribed to their captivity. Other species for which similar “explanations” have been proposed (including appeals to factors such as crowding and/or stress in captivity) include Common Chimpanzees, Gorillas, Stumptail Macaques, Musk-oxen, Koalas, Long-eared Hedgehogs, Vampire Bats, and Black-crowned Night Herons.⁹² Sometimes the only context where same-sex activity is discussed is to exemplify the types of “pathologies” that arise in captivity. Homosexuality in Dolphins, for instance, was offered as an illustration of the “sexual aberrancy” that can result from confinement in aquariums, while a case of female coparenting in Barn Owls was included in a report on “Abnormal and Maladaptive Behavior in Captive Raptors”—part of a monograph on (of all things) diseases in birds of prey. Homosexual activity in Rhesus Macaques was even presented (along with a number of other “abnormal” behaviors) as an illustration of the deleterious effects of malnutrition.⁹³ In a perfect example of the sort of circular reasoning that is employed in many scientific discussions, homosexuality in captive animals is often cited as the “proof” of the artificiality of their captive conditions. One zoologist proclaims, “Homosexual behavior [in Cheetahs] … is reported in zoos as quite frequent, which to me indicates that something is amiss at the zoos,” while another states, “The very occurrence of female-female pairs [in Zebra Finches] suggests behavioral pathology.”⁹⁴ This is chillingly reminiscent of the not-so-distant “medicalized” views of human homosexuality, where the mere existence of same-sex attraction or activity was sufficient to “diagnose” pathology or mental illness.

While it is true that captivity sometimes does induce unusual behaviors in animals, the bulk of the evidence does not support this as a “cause” of animal homosexuality. As primatologist Linda Fedigan observes, “Although … homosexual relationships in animals can occur as a result of stressful captive conditions, we would suggest that all such behavior should not be dismissed as pathological or dysfunctional, a practice which results in ‘explaining it away’ rather than explaining it.”⁹⁵ On statistical grounds alone there is no substantiation for a greater incidence of homosexuality in captive animals—in fact, just the reverse is true. In more than 60 percent of the mammals and birds in which same-sex activity has been documented, this behavior occurs spontaneously in the wild. In more than two-thirds of these species, homosexuality has only been observed in the wild, while in the remaining cases it occurs in both wild and captive animals.⁹⁶ A number of scientists have remarked on a higher rate of homosexual activity in captivity compared to in the wild when the behavior occurs in both situations. In other words, there may be a quantitative, rather than qualitative, difference between wild and captive conditions, although the occurrence of homosexuality itself cannot be attributed to confinement. However, even this difference is less than clear-cut. In some species such as Orang-utans, Hamadryas Baboons, Mule Deer, and Musk-oxen, there does indeed appear to be a higher rate of homosexual courtship and/or sexual activity—as well as heterosexual activity—in captivity compared to the wild, although in some instances this is based on impressionistic observations.⁹⁷ In contrast, two species for which detailed quantitative information is available show nearly identical rates of same-sex activity in the wild versus captivity: in Bonobos, studies of wild animals have revealed that 45–46 percent of all sexual activity is homosexual, while a captive study yielded a figure of 49 percent; in Black Swans, one investigator found that 5 percent of captive pairs were homosexual while 6 percent of wild ones were.⁹⁸

Failure to observe homosexuality in the wild is more often due to incomplete study or inadequate observational techniques rather than an actual absence of the behavior in free-ranging animals. Time and again, same-sex activity has initially been seen only in captive animals and therefore declared to be definitively not a part of the “normal” sexual repertoire of the species in the wild. Yet when detailed field studies of the same species are finally conducted—often decades later—homosexuality is inevitably discovered. In fact, so pervasive or routine is the behavior now known to be for some species in the wild, that scientists have had to completely revise prior assessments of same-sex activity as “artificial” for these animals in captivity. In Bottlenose Dolphins, for example, male pairs engaging in homosexual behavior were originally observed in aquariums and were considered to be the “aberrant” result of keeping males together without females. Detailed longitudinal and demographic studies of the species—more than forty years later—revealed that male pairs, as well as sex segregation, are a prominent feature of the social organization of this species in the wild. By 1998, zoologists were actually advocating that captive male Bottlenose Dolphins be kept (and reintroduced into the wild) as bonded pairs, recognizing that these constitute a “natural functional social unit” of the species that can assist captive individuals in adjusting to life in the wild upon their release. Another example of a complete turnaround on the part of scientists concerns Gorillas. Early studies of this species reported that homosexuality was not seen in wild Gorillas; three decades later, extensive same-sex activity had been documented in both males and females in the mountain forests of Africa. By 1996, biologists and zookeepers were (at last) openly acknowledging that homosexuality in all-male groups was not an “artificial construct of captivity,” and were even encouraging the formation of such groups in zoos to approximate the species’ natural social patterns.⁹⁹

Many other examples of field studies confirming earlier captive observations of homosexuality (and disproving initial assessments of its “artificiality”) can be found. In 1935, Konrad Lorenz asserted that the formation of same-sex pairs in female Jackdaws “does not appear to occur under natural conditions”; it wasn’t until more than forty years later that ornithologists confirmed the occurrence of homosexual pair-bonding in wild Jackdaws. Same-sex activities between male Elephants in captivity were first reported in the scientific literature in 1892 and characterized as “aberrations” and “perversions”; almost 75 years later, similar and more extensive homosexual interactions were documented among wild Elephants. In 1997 zoologists presented the first descriptions of same-sex activities in wild Crested Black Macaques, finally confirming captive observations made more than thirty years earlier. Because no detailed field studies of this species had been conducted before the 1990s, all prior reports of homosexual activity were based on observations in captivity, leading some scientists to suggest that same-sex activity was not likely to be found in wild Crested Black Macaques—a prediction we now know was incorrect. Homosexual pairing in Parrots was long considered to be “induced or brought forth by the conditions of confinement,” but in 1966 an ornithologist documented a male pair of Orange-fronted Parakeets in the forests of Nicaragua—the first confirmation of homosexuality in wild Parrots. Ironically, the sex of the birds was verified only because the scientist mistook them for a heterosexual pair copulating unusually early in the breeding season (and therefore he wanted to check the condition of their internal reproductive organs). Initial observations of homosexuality in captive female Lions, made in 1942, were confirmed in the wild in 1981, while observations of male pairs in wild Great Cormorants in 1992 corroborated early observations of this phenomenon among zoo birds in 1949. Likewise, same-sex courtship in Regent Bowerbirds was first described on the basis of aviary observations in 1905, but display between wild males was not documented until nearly a century later. And homosexual activity between different species of Dolphins, long observed in aquariums, was finally verified in a wild population in 1997.¹⁰⁰ Today, homosexuality in many species is still known only from captive studies, but it is likely that most, if not all, of these will follow this same pattern and eventually be confirmed by field studies. Perhaps it is finally time for scientists to acknowledge that homosexuality in captive animals is nearly always an expression of their normal behavioral repertoire, rather than a result of their captivity.

Another point to keep in mind is that the distinction wild versus captive is in some sense a false dichotomy, since in actuality there is a continuum of degrees of confinement, “artificiality,” and human intervention in the living conditions of animals. At one extreme are truly “wild” animals that have experienced no, or virtually no, contact with humans—an increasingly rare phenomenon in the contemporary world. At the other extreme are domesticated animals that have been bred and raised in captivity for many generations, often to the point of being genetically distinct (as a separate species or subspecies) from their wild counterparts. In between, there is a whole spectrum of contexts and factors. Toward the more “wild” end of the continuum, there are free-ranging species that have nevertheless experienced varying degrees of human contact or interference, such as Killer Whale populations that have been heavily poached, or wild Tree Swallows that nest in colonies of human-supplied nest boxes, or Grizzly Bears living in “disturbed” habitats, or wild Atlantic Spotted Dolphins that are habituated to the presence of people.¹⁰¹ There are also semi-wild animals, a cover term that includes a host of different situations. For instance, unconfined animals may nevertheless be tame (e.g., Greylag Geese), while animals on reserves may be wild or “free-ranging” within a confined but extensive territory, often hundreds or thousands of acres in size (e.g., Bison, Cheetahs). Transplanted populations consist of entire troops or herds that have been moved, their social organization and demographics intact, to a new (often more restricted) environment, sometimes because they are endangered in their natural habitat (e.g., Rhesus Macaque troops transplanted from India to Puerto Rico, Blackbuck herds moved from India to France). Another semi-wild situation involves animals that are recently extinct in the wild and therefore can only be observed in captivity (e.g., Takhi, Père David’s Deer). In many cases such species are kept in conditions that approximate their “former” wild habitat and social organization as closely as possible, and in some instances they are even being slowly reintroduced to the wild from their captive populations. “Provisioned” animals are wild but supplied with food and varying amounts of human contact (e.g., Japanese Macaques), while “rehabilitated” animals are formerly captive (and possibly wild-born), but reintegrated into wild populations (e.g., Orang-utans). Finally, feral species are domesticated animals that have escaped and “gone wild,” establishing their own free-ranging populations (e.g., Water Buffalo, Mute Swans, Rock Doves).

Among captive animals, a wide variety of factors—each of which represents a continuum of its own—must also be considered when assessing the “artificiality” of their confinement: Are the animals wild-born or raised in captivity? Are they tame and/or trained, or do they have little or no contact with humans? Are they free-ranging within an outdoor enclosure (e.g., at a zoo or wild-animal park) or are they kept in restrictive cages (e.g., in a laboratory)? Are they living in mixed-sex groups or sex-segregated groups—and which is typical of wild populations? How closely does their social organization in captivity approximate that of wild animals, in terms of the size and number of social groups, the sex and ages of the animals making up those groups, and the transiency or stability of such groups? With regard to the occurrence of homosexuality, virtually every situation along this continuum—and every semi-wild context—has been claimed to be “artificial” to one degree or another, or else “natural” enough not to warrant concern. Yet the fact that homosexuality has been observed in virtually every one of these contexts argues for the relative independence of this behavior from whatever conditions of “captivity” or “wildness” may prevail. Moreover, what constitutes a “natural” captive context is often directly counter to preconceived ideas. Regarding Cheetahs, for example, a number of researchers have commented that keeping males and females together in captivity is actually something of an “artificial” situation (since it seems to contribute to an inhibition of heterosexual courtship and mating); conversely, same-sex pair-bonds appear to be integral to the “psychosocial well-being” of males. Ironically then, sex segregation in captivity is actually more “natural” for this species, since it reflects the Cheetah’s social organization in the wild (a situation that is also true for many other species in which males and females typically live apart from each other).¹⁰²

It should also be pointed out that something of a double standard exists regarding what is interpreted as “natural” as opposed to “captivity-induced” behavior. It is common zoological practice, for example, to study mate choice in pair-bonding species (such as birds) by setting up captive situations where individuals are only given a “choice” of opposite-sex partners. It is also standard practice to keep zoo animals strictly in heterosexual pairs for breeding purposes. Thus, a sizable portion of reported “heterosexual” behavior is in fact based on situations that would be considered “artificial” if they were used to study homosexual behavior. In other words, if animals are kept only with members of their own sex and then subsequently exhibit homosexual activity, this is overwhelmingly interpreted as “situational” behavior that would not otherwise happen. In contrast, if they are only given access to opposite-sex partners and subsequently exhibit heterosexual behavior, this is without exception interpreted as an expression of their “natural” tendencies. Although researchers readily regard homosexuality to be the result of external or artificial factors operating on otherwise heterosexual animals, no one has dared suggest that the reverse situation might also sometimes occur—that heterosexuality could be “forced” on otherwise homosexual (or largely same-sex-oriented) animals. In fact, zoos and other captive breeding programs offer countless reports of animals “failing” to breed in captivity for no apparent reason when placed with opposite-sex partners. Even after exhausting the long list of factors that could be involved, animal breeders uniformly overlook the possibility that some of these individuals may simply have a preference for same-sex activities and/or partners.

In the majority of species where homosexuality has only been observed in captive or semi-wild conditions, researchers have confirmed that other aspects of behavior or social organization in captivity—including sexual behaviors—are comparable to those of wild animals. In some instances, behaviors once considered to be “abnormal,” “artificial,” or “unusual” products of captivity have also been documented in the wild. For example, Botos frequently play with man-made objects in aquariums (carrying and manipulating rings, brushes, and so on) and also interact playfully with animals of other species kept in their tanks. Wild Botos have also been observed in similar behaviors, playing with sticks, logs, fruit pods, and even fishermen’s paddles, as well as with other species such as river turtles. Tool use and manufacture by Orang-utans had long been known from studies of captive and semi-wild animals, but until the behavior was documented in wild Orang-utans in 1993, it was considered typical only of “artificial” situations. One researcher, studying captive Savanna Baboons, asserted that “certain types of behavior such as copulation during pregnancy or lactation may be related to caged life, and not be the norm in natural populations,” yet later studies of wild populations revealed that these behaviors do in fact occur regularly. Likewise, until it was documented in the wild, cross-species herding behavior by male Thomson’s Gazelles was thought to be caused by the unavailability of same-species groupings in captivity. Parenting trios, mate-switching, promiscuous copulations, and egg stealing were all initially observed in captive King Penguins and considered to be “unusual” (if not “abnormal”) behaviors. Yet detailed study of this species in the wild nearly thirty years later verified the occurrence of each one of these activities, as well as many other “unexpected” behavioral patterns. In a few cases, a more “unusual” behavior has only been documented in wild populations, or else is more prevalent in the field than in captivity: for example, reverse mounting in Black-headed Gulls and divorce in Flamingos.¹⁰³ Thus, while homosexuality has not yet been observed in many of these species in the wild, it is probably only a matter of time before it is.

Other situations involving homosexuality in captive animals also occur. Often same-sex activity in one species has only been observed in captivity (e.g., Siamangs, Mute Swans, Sociable Weavers), yet a closely related animal does exhibit similar or identical behavior in the wild (e.g., White-handed Gibbons, Black Swans, and Gray-capped Social Weavers, respectively). In other cases, one form of homosexuality is seen in captivity and another form in the wild. In Griffon Vultures, for example, homosexual pairs and sexual activity have been observed in captivity while same-sex courtship and pair-bonding display flights have been seen in the wild. In Emus, sexual activity between males has been documented in captivity and male coparenting in the wild. In Galahs, homosexual pairs have been observed extensively in captivity but not in the wild, although “supernormal clutches”—nests with double the number of eggs, typical of female pairs in other birds—have been verified in the field. And in Cheetahs, same-sex courtship and sexual activity have been seen in captivity while male pair-bonds have been observed in both wild and captive animals. This suggests that the absence of certain behaviors in studies of wild animals are probably accidental “gaps” that will be filled once more extensive field studies are conducted. This is particularly likely when one considers that the proper observational techniques for identifying homosexual activity are often not employed, even in species where same-sex activity has previously been verified in captivity. In the most recent ongoing field studies of Griffon Vultures, for example, the sex of birds is determined “behaviorally” by their position during mounting (top bird = male, bottom bird = female), or not verified at all, thereby precluding the possibility of detecting homosexual pairs. “Behavioral” sexing has also been employed in the major long-running studies of large populations of wild King Penguins, Gentoo Penguins, and Flamingos—in some cases combined with “morphological” sexing, i.e., the larger bird in a pair is assumed to be male and the smaller female, without actual verification of sex—all species in which same-sex pairs have been observed in captivity but not yet documented in the wild. And the sex of wild Dugongs participating in mating behavior has never been unequivocally determined in nearly two decades of field observations; researchers invariably assume that the interactions are heterosexual, even though same-sex activity has been observed in captivity (and in the wild in the related West Indian Manatee).¹⁰⁴

It must also be remembered that it is often extremely difficult to observe some species in the wild or obtain detailed information about their behavior. Many animals in which homosexuality has only been seen in captivity present formidable challenges to field study. Some are nocturnal (active only at night) or crepuscular (active at dusk or dawn), such as Lesser Bushbabies (and other Lemurs), Wolves, Rufous Bettongs, and Black-crowned Night Herons. Others are diurnal (active in the daytime) but engage in sexual behavior mostly at night (e.g., Red Deer). This can greatly hamper efforts to observe sexual activity: homosexual mounting in Red Foxes, for example, was only discovered by setting up remote-control infrared video cameras to continuously monitor nighttime activities in a captive population—virtually impossible to do under field conditions. Other species are highly elusive: Bush Dogs, for example, have rarely even been sighted in the wild, let alone studied, and the most complete analysis of their social organization in captivity was only published in 1996. Likewise, the elusiveness of Pig-tailed Macaques precluded detailed field observations until the early 1990s, while the first in-depth behavioral studies of wild Crested Black Macaques were published in 1997. Sometimes the inaccessibility of the animal’s habitat poses nearly insurmountable hurdles: Siamang Gibbons, for example, frequent the jungle canopy as much as 120 feet above the ground, and homosexuality in the closely related, and equally arboreal, White-handed Gibbon was not discovered in the wild until 1991. Whales and Dolphins spend less than 20 percent of their time at the surface of the water, and underwater observation (where sexual activity often occurs) is frequently impractical.¹⁰⁵ This is compounded by the fact that recognition of individual animals and determination of their sex—essential for obtaining detailed behavioral data—is also usually extremely difficult. An animal’s size can also be a factor: few behavioral observations of wild Apereas have been made because they are so small and their social activities are often hidden in dense grass and brush. Small size (among other factors) also hampers field observations of Squirrel Monkeys, Rufous-naped Tamarins, and Rufous Bettongs. The latter species is also largely asocial