Biological Exuberance: Animal Homosexuality and Natural Diversity

Affectionate activity often leads to, or is inseparable from, overtly sexual behavior—defined here as any contact between two or more animals involving genital stimulation. Stumptail and Crab-eating Macaques, for example, kiss their same-sex partners during sexual mounting. In fact, mounting is the most common type of sexual behavior found in homosexual contexts: one animal climbs on top of the other in a position similar to heterosexual intercourse, usually from behind in a front-to-back position (that is, one animal mounted on the back of the other). More than 95 percent of mammal and bird species use this position, for both male and female homosexual interactions. On the other hand, some animals—particularly primates such as Gorillas, Bonobos, and White-handed Gibbons—use a face-to-face position (in addition to, or instead of), and in some cases this is more common in homosexual encounters than in heterosexual ones. Belly-to-belly copulation is also the norm for both homosexual and heterosexual interactions in Dolphins. Occasionally more unusual or “creative” mounting positions are used, particularly by female animals. In Bonobos, Stumptail Macaques, and Japanese Macaques, for instance, females sometimes interact in a supine or semirecumbent position, one individual behind the other with her partner between her legs or sitting “in her lap” (which may also be done in a face-to-face position). Occasionally female Warthogs, Rhesus and Japanese Macaques, Koalas, and Takhi mount their female partner from the side rather than from behind; lateral mounts also sometimes occur during heterosexual interactions in these (and other) species. And in some animals a “backward,” head-to-tail mounting position is occasionally used, e.g., in Botos, Hammerheads, Ruffs, and Western Gulls. Most same-sex interactions involve only two individuals at a time, but group sexual (and courtship) activity—involving anywhere from three or four (Giraffes, Lions) to six or more (Bowhead Whales, Mountain Sheep) partners—occurs in over 25 different species.

The actual type of genital contact varies widely. Full penetration in male anal intercourse occurs in some species (for example, Orang-utans, Rhesus Macaques, Bison, and Bighorn rams), while female penetration of various types occurs during lesbian interactions in Orang-utans (insertion of the finger into the vagina), Bonobos (insertion of the erect clitoris into the vulva), and Bottlenose and Spinner Dolphins (insertion of a fin or tail fluke into the female’s genital slit). Simple pelvic thrusting and rubbing of the genitals on the rump of the other animal is widespread in both male and female homosexual mounts (occurring in the Northern Fur Seal, Lion, and Proboscis Monkey, among others), and simple genital-to-genital touching is the form of homosexual (and heterosexual) contact in species where males do not have a penis (as in most birds, such as the Pukeko and Tree Swallow). A more unusual type of male homosexual contact involves various forms of non-anal penetration. In Whales and Dolphins, both males and females have a genital slit or opening; when not aroused, the male’s penis is contained in the cavity leading to this slit. Homosexual activity in Bowhead Whales, Bottlenose Dolphins, and Botos sometimes involves insertion of the penis of one male into the genital slit of the other. Other more unusual forms of penetration have also been documented: male Botos occasionally insert the penis into a male partner’s blowhole (on the top of his head!), while male Orang-utans have even been observed retracting their penis to form a sort of “hollow” or concavity that another male can penetrate. Clitoral rubbing or other types of genital tribadism are found in female Bonobos, Gorillas, and Rhesus Macaques (among others), while males in several species (e.g., White-handed Gibbons, West Indian Manatees, and Gray Whales) rub their penises together or on each other’s body. In male Bonobos, mutual genital rubbing sometimes takes the form of an activity with the colorful name of “penis fencing,” in which the males hang suspended by their arms and rub their erect organs against each other.