Biological Exuberance: Animal Homosexuality and Natural Diversity

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