Biological Exuberance: Animal Homosexuality and Natural Diversity

In other animals the very characteristics that are used to claim that same-sex activities are nonsexual—their briefness, “incompleteness,” or absence of signs of sexual arousal, for example—are as typical, if not more typical, of opposite-sex interactions that are classified as sexual behavior. Nearly a third of all mammals in which same-sex mounting occurs also have “symbolic” or “incomplete” heterosexual mounts in which erection, thrusting, penetration, and/or ejaculation do not occur; “ritual” heterosexual mountings are also typical of many bird species.¹⁰⁹ In Kob antelopes, 52 percent of heterosexual copulations involve at least one mount by the male without an erection; in contrast, 56 percent of homosexual mountings between male Giraffes—sometimes classified as nonsexual—do involve erections. Likewise, only one in four to five heterosexual mounts among northern jacanas results in cloacal (genital) contact, and ejaculation probably occurs in less than three-quarters of Orang-utan heterosexual mounts.¹¹⁰ Evidence for sexual arousal or “completed” copulations is often entirely lacking in heterosexual contexts, yet such male-female mounts are still considered “sexual” behavior. In Walruses, Musk-oxen, Bighorn Sheep, Asiatic Mouflons, Grizzly Bears, and Olympic Marmots, for example, penetration and ejaculation are rarely, if ever, directly observable during heterosexual mounts, while male erections are routinely not visible during White-tailed Deer copulations, ejaculation can only be “assumed” to occur in observations of Orang-utan, White-faced Capuchin, and Northern Fur Seal heterosexual mating, and genital contact is difficult to verify during Ruff male-female mounts (among many other species).¹¹¹

In fact, actual sperm transfer during heterosexual copulations in many species is so difficult to observe that biologists have had to develop a variety of special “ejaculation-verification” techniques. In birds such as Tree Swallows, for example, tiny glass beads or “microspheres” of various colors are inserted into males’ genital tracts. If the birds ejaculate during a heterosexual mating, these beads are transferred to the female’s genital tract, where they can be retrieved by scientists and checked for their color coding to determine which males have actually transferred sperm. For rodents and small marsupials, biologists actually inject several different radioactive substances into males’ prostate glands. During ejaculation, these are carried via semen into females, who are then monitored with a sort of “sperm Geiger counter” to determine which males, if any, have inseminated them.¹¹² If such elaborate lengths are required to verify a fundamental and purportedly self-evident aspect of heterosexual mating, is it any wonder that homosexual matings should sometimes appear to be “incomplete”?

Because of such difficulties in observation and interpretation, scientists have often employed similarly extreme measures in an attempt to “verify” homosexual intercourse. In the early 1970s, for example, a controversy arose concerning to what extent, if at all, mounting activity between male animals was truly “sexual.” As proof of its “nonsexual” character, some scientists claimed that full anal penetration never occurred in such contexts (thus equating penetration with “genuine” sexuality). Researchers actually went to the trouble of filming captive male Rhesus Macaques mounting each other in order to record examples of anal penetration; they even anesthetized the monkeys afterward to search for the presence of semen in their rectums. Needless to say, the cinematographic proof of anal penetration they obtained did little to quell any subsequent debate about whether such mounts were “sexual”—all it did was institute a revised definition of “sexual” activity. The fact that they were able to document penetration but not ejaculation simply meant that a new “standard” of sexuality could now be applied: only mounts that culminated in ejaculation were to be considered “genuine” sexual behavior. Ironically, none of these researchers were apparently aware of an earlier field report of homosexual activity in Rhesus Macaques in which both anal penetration and ejaculation were observed.¹¹³