It is certainly true that homosexual repertoires have a wider range of sexual acts than heterosexual repertoires in a number of species. In Stumptail and Crab-eating Macaques, for instance, oral sex and mutual masturbation occur primarily, if not exclusively, between same-sex partners. Male Bonobos have a form of mutual genital rubbing known as penis fencing that is unique to same-sex interactions. Male West Indian Manatees employ a wider variety of positions and forms of genital stimulation during sex with each other than do opposite-sex partners. Various types of anal or rump stimulation (besides mounting or intercourse) occur in homosexual but not heterosexual contexts in several Macaque species, Siamangs, and Savanna Baboons. Only same-sex partners participate in reciprocal mounting in at least 15 species, including Bonnet Macaques, Mountain Zebras, Koalas, and Pukeko.43
This does not, however, appear to be part of an overall pattern, especially where sexual activities other than mounting or intercourse are concerned. For example, of the 36 species (exhibiting homosexual behavior) in which some form of oral sex is practiced, in only 10 (28 percent) of these is oral-genital stimulation limited to homosexual contexts, and in some cases (e.g., Rhesus Macaques, Caribou, Walruses, Lions) genital licking is a uniquely heterosexual act. Similarly, manual stimulation of the genitals or masturbation between partners is limited to same-sex interactions in 15 of the 27 species (55 percent) where this behavior occurs; in the remaining animals, both heterosexual and homosexual (or, in some cases, only heterosexual) partners are involved. Even anal or rump stimulation (besides intercourse) is found in heterosexual contexts in half of the species (6 of 12) that engage in such activities. Combining these observations, we find that a variety of sexual acts are part of both heterosexual and homosexual repertoires in the majority of cases, with behaviors unique to same-sex interactions occurring only in about 40 percent of the cases.
As a matter of fact, in most instances both heterosexual and homosexual acts are equally “uninspired,” involving nothing more exotic than mounting behavior in the front-to-back position typical of mating in most animals. Even considering animals where other mounting positions are used, however, it is overly simplistic to claim that same-sex activity involves more “versatility.” In many species a variety of positions are employed in both heterosexual and homosexual situations. Furthermore, even though their frequency of use differs depending on the context, the major distinctions in mounting positions often lie along lines of gender rather than sexual orientation. The differentiating factor is not whether sexual activity involves partners of the same or opposite sex, but whether it involves males (in either heterosexual or homosexual contexts). For example, a face-to-face position is used for roughly 99 percent of sexual interactions between female Bonobos, but rarely in male-female interactions. However, a face-to-face position is almost equally rare in male homosexual interactions, occurring in only about 2 percent of activity between males. Thus, male homosexuality is more similar to heterosexuality than either is to female homosexuality in terms of the frequency of use of these two basic positions. A similar pattern occurs in Gorillas: although the face-to-face position is virtually absent in heterosexual encounters and much more common in homosexual ones, the two sexes have almost opposite preferences for this position. Almost three-quarters of female homosexual encounters involve the face-to-face position, while more than 80 percent of male homosexual mountings involve the front-to-back position (also preferred for heterosexual encounters). In Hanuman Langurs, male homosexuality is also more similar to heterosexuality than is female homosexuality in terms of the way that interactions are initiated: both males and females typically invite males to mount them by performing a special “head-shaking” display, which is much less characteristic of mounting between females.44
In Japanese Macaques, female homosexuality is more similar to heterosexuality than to male homosexuality in terms of the variety of positions used. In contrast, male homosexuality is more similar to heterosexuality than female homosexuality in terms of the frequency that various positions are used. In this species, fully seven different mounting positions can be identified, including four varieties of the front-to-back posture (with the mounting animal sitting, lying, or standing—with or without clasping its partner’s legs—behind the mountee), two types of face-to-face positioning (sitting or lying down), and sideways mounts. All seven of these positions are found in both heterosexual and female homosexual encounters, while male homosexual mounting employs only five of the seven (sitting or lying on the partner in a front-to-back position are not used). However, sexual encounters between females differ from both heterosexual and male homosexual mounts in using the face-to-face position more often, and in using the double-foot-clasp posture less than 20 percent of the time (compared to 75–85 percent of the time for sexual encounters where males are involved, either heterosexual or homosexual).45
Other patterns based on the intersection of gender and sexual orientation also occur. In Stumptail Macaques, for example, female homosexual encounters use three basic positions (standing or sitting front-to-back and sitting face-to-face), heterosexual activity uses two of these (standing or sitting front-to-back), while male homosexual activity uses only one of these (standing front-to-back). (Males do, however, employ a wider range of oral and manual forms of genital stimulation in their encounters with each other.) Copulations between female Flamingos generally resemble heterosexual matings more than they do mountings between male Flamingos, but same-sex copulations in birds of either sex differ from heterosexual activity in their lack of a particular “hooking” posture.46 Male White-handed Gibbons interact sexually with other males only in a face-to-face position and with females only in a front-to-back position—thus, homosexual and heterosexual interactions are equally “flexible” or “inflexible” in this species, but differ in which position is preferred in each context. Even reciprocal or reverse mounting—in which partners take turns mounting each other—is part of the heterosexual repertoire in more than three-quarters of the species that engage in this activity (in either same-or opposite-sex contexts); it is unique to heterosexual relations in many of these (including Western Gulls and Silvery Grebes) and present in many animals that do not engage in homosexual behavior at all.
Female Japanese Macaques in a sexual embrace. This face-to-face position is less common during heterosexual and male homosexual interactions.
In fact, it is sometimes the case that opposite-sex partners show more variability or flexibility in their sexual activity Heterosexual copulation in Botos occurs in three main positions (all belly-to-belly, either head-to-head, or head-to-tail, or at right angles) while homosexual copulation usually uses only one of these (head-to-head). 47 Both heterosexual and homosexual encounters in this species can involve two different forms of penetration (genital slit or blowhole), although same-sex activity also includes a third option, anal penetration. Among birds, the overwhelming majority of species mate in the standard position of one individual mounted on the other’s back, in both heterosexual and homosexual contexts. The only examples of other positions being used with any regularity involve male-female mounts: a facing position (extremely unusual for birds) is used by stitchbirds, for instance, who mate with the female lying on her back and the male on top of her, and in purple-throated Carib hummingbirds, who mate belly-to-belly while perched on a branch. Copulation in red-capped plovers is achieved by the male first throwing himself on the ground on his back, then pulling the female on top of him in a facing position. Vasa parrots have an elaborate and (for birds) unusual form of genital contact in which the male inserts his genital protrusion (a bulbous swelling surrounding his genital orifice) inside the female’s cloaca, which extends and envelops his organ while the two birds transfer from a regular mounting position to a side-by-side position (full penetration does not usually occur in bird matings). Vervain hummingbirds actually mate in midflight while traversing an 80-foot trajectory low above the ground. Finally, several species of woodpeckers are true heterosexual virtuosos: in an acrobatic sequence the male first performs a standard front-to-back mount and then drops to one side of the female, making genital contact with his tail underneath hers and sometimes ending up on his back or with his entire body in a perpendicular or even upside-down position.48