Biological Exuberance: Animal Homosexuality and Natural Diversity

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 or solitary, a problem encountered as well in Bears and numerous other carnivores, where many thousands of hours of observation in the field often yield precious little information about social or sexual interactions.

Because sexual activity in Red Foxes usually takes place at night, scientists were only able to document homosexual activity by using remote-control video cameras, set up in an enclosure illuminated by infrared light. In these two stills taken from the videotape, a younger female Red Fox mounts her mother.

Even for species that are not difficult to observe, enormous time must still be invested in observation and quantification of behaviors before a reasonably complete picture of the animals’ habits can be pieced together. Zoologists have estimated that to obtain a good working understanding of a species, three field-workers would need to invest two years and 2,000 hours of observation time—yet even this may not be enough. Over a dozen scientists studying Orang-utans, for example, have collectively spent more than ten times this amount—20 years and a combined total of 22,000 hours of field observation—yet they admit that many aspects of the behavior of this species are still poorly understood. Likewise, zoologists involved in a comprehensive study of Oystercatcher behavior in the wild did not observe homosexual activities until nearly a decade into their research project.¹⁰⁶ It’s no wonder, then, that many behaviors, including homosexuality, are just beginning to be documented in the wild or have yet to be observed outside of captivity. In summarizing wild versus captive comparisons of animal behavior, Jane Goodall has remarked, “If a primate shows behavior in captivity which has not been observed in the wild, this by no means implies that it does not occur in the wild.”¹⁰⁷ The history of the study of animal homosexuality has shown this to be a truism, not just for primates, but for all species.

Hormonal Imbalances and Other Monstrosities

Unable to find any other “reason” for same-sex activity in animals, many scientists have tried to argue that homosexuality is itself a physical abnormality or the manifestation of some pathological condition. The most common physiological “malfunctions” that are suggested to “explain” homosexual behavior in animals are some sort of hormonal imbalance, and an “abnormal” condition of the sex organs. Female Sage Grouse who court and mount other females are described as suffering from “hormonal or hermaphroditic irregularities,” for example, while scientists speculate on the “endocrine balance” of female Rhesus Macaques that participate in homosexual activity, the possible “hormonal defects” of female Fat-tailed Dunnarts that mount other females, and the influence of “abnormal physiological particulars” on the lesbian behavior of Long-eared Hedgehogs. Scientists have even suggested that homosexual mounting by Takhi mares who are pregnant is due to the male hormones circulating in their system as a result of carrying a male fetus.¹⁰⁸

Scientific studies of homosexuality often seek evidence of “irregularities” in the form or condition of an animal’s sex organs. This reflects in large part the widespread misconception (stemming from early sexological discussions of humans) that homosexuality is tantamount to hermaphroditism—i.e., any gender “transgression” is mapped onto an anatomical or physiological “abnormality.” In 1937, scientists carefully examined the external genitalia of a male Common Garter Snake that had engaged in sexual behavior with another male to verify that it had “normal” male sex organs (it did). They then killed and dissected the animal to see if it had female gonads, reporting “no ovarian tissue was discovered.” Lest one think this merely reflects the outmoded views of the time, nearly 60 years later this scenario was repeated with uncanny parallelism. In 1993 scientists performed a laparotomy (a surgical technique to examine the internal sexual organs) on a male Hooded Warbler that repeatedly formed homosexual pairs, in order to verify its sex and determine the condition of its male organs; the bird was later killed to obtain tissue samples. They reported that his sex organs were indistinguishable from other males’, adding—in words echoing those used more than half a century earlier—“No ovarian tissue was present.”¹⁰⁹ Just as early medical descriptions of homosexuality in humans often focused attention on the supposedly abnormal development or condition of the external genitals (along with hormonal factors), so, too, have scientists studying same-sex activity in animals tried to link this behavior to genital “peculiarities.” In describing male companions in African Elephants, one zoologist emphasized that animals in such partnerships may exhibit physical “defects” including “enlarged external genitalia,” while an ornithologist describing a male Snow Goose in a homosexual pair felt compelled to remark, “His much enlarged penis indicated a strong endocrine stimulation.”¹¹⁰

There is no evidence to support a hormonal or other physiological “explanation” of animal homosexuality, and there is considerable evidence against it. Comprehensive and rigorous endocrinological analyses, as well as gonad measurements, of homosexual Western and Ring-billed Gull females show conclusively that there are no significant hormonal or anatomical differences between birds in homosexual and heterosexual pairs that could account for same-sex pairing. Specifically, investigators found that females in homosexual pairs are not hormonally “masculinized,” i.e., they do not have higher levels of male hormones (androgens) than do females in heterosexual pairs. If anything, homosexual females may be more hormonally “feminine” than heterosexual females: some lesbian Ring-billed Gulls actually have significantly higher levels of progesterone, a female hormone associated with nest-building and incubation behavior.¹¹¹ Likewise, studies of a variety of primate species have shown no correlation between hormone levels and homosexual activity.¹¹²

Conversely, researchers have found hormonal differences between individuals in some species that exhibit homosexual behavior, but not in animals that participate specifically in same-sex activity. Endocrinological studies of Pied Kingfishers, for example, reveal that some males have lowered testosterone levels (as well as smaller gonads), but these individuals constitute one class of nonbreeding “helpers” who assist their parents in raising young. Few, if any, such males are involved in the homosexual pair-bonding or mounting activity that sometimes occurs in this species. Likewise, a certain category of nonbreeding Orang-utans (those with “flanges”) often have elevated estrogen levels—but homosexual activity is neither characteristic of, nor exclusive to, such individuals. In other species scientists have determined that an “unusual” hormonal profile is found in the majority of individuals, but this is not linked to homosexual activity. In Spotted Hyenas, females generally have higher levels of a particular “male” hormone (a type of androgen) than do males, yet only a fraction of them actually participate in same-sex mounting; moreover, pregnant females also have elevated levels of testosterone (regardless of the sex of their fetus) but are not more prone to same-sex mounting. Likewise, all female Western Gulls have high levels of androgens (including testosterone)—nearly equal to those of males—regardless of whether they are in homosexual or heterosexual pairs.¹¹³ These examples illustrate another important point: in many species a portion of the population routinely exhibits hormonal profiles (or other physiological characteristics) that differ from the “norm”— sometimes correlated with nonbreeding—yet only when individuals display overt homosexuality or transgender is the label of abnormality or dysfunction applied.

In most instances where a physiological “explanation” is advocated, this is purely conjectural, not based on any actual hormonal studies of the animals involved, and often highly improbable on independent grounds. For example, the connection between male fetal hormones and a pregnant mother’s behavior—advocated as an “explanation” for mounting among female Takhi—is entirely speculative, since endocrinological profiles were not drawn up for the specific individuals involved in same-sex activity. Moreover, even if there were a connection, it would be at most only a partial explanation for this (and other) species. One Takhi mare mounted males when carrying a male fetus rather than mounting other females and also failed to show similar behavior the next year when she was again pregnant with a male fetus.¹¹⁴ Thus, additional factors must be involved in determining whether such mares participate in homosexual, bisexual, and/or heterosexual (reverse) mounting behavior, if any of these. More generally, this explanation does not have wide applicability to other species. For example, only a fraction of Domestic Horses (which are closely related to Takhi) ever show mounting behavior of any sort when pregnant.¹¹⁵ In addition, homosexual behavior by pregnant females occurs in less than 8 percent of all mammals in which female homosexual mounting has been documented, and in none of these species is the behavior exclusive to pregnant females