Biological Exuberance: Animal Homosexuality and Natural Diversity

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

“Virtuosity” in other areas of behavior is not generally exclusive to homosexual encounters either. The vast majority of courtship interactions, for example, involve the same set of behaviors typical for the species regardless of whether they are being performed between partners of the same or the opposite sex. There are notable exceptions, of course: the courtship “games” of female Rhesus Macaques and solicitations of female Japanese Macaques; “necking” interactions between male Giraffes; pirouette dances in male Ostriches; the vocal duets of Greylag gander pairs; aspects of courtship feeding in Laughing Gulls, Antbirds, Superb Lyrebirds, and Orange-fronted Parakeets; alternative bower displays in Regent Bowerbirds; and unique vocalizations during homosexual but not heterosexual interactions in male Emus and Japanese Macaques. Occasionally courtship activities are also performed at different rates or with different intensities: in same-sex pairs of Black-winged Stilts and Black-headed Gulls, for instance, certain courtship behaviors occur more frequently in same-sex pairs, others more commonly in opposite-sex pairs. All of these represent behavioral innovations in same-sex contexts, but they are atypical. Usually both homosexual and heterosexual courtships draw upon the same repertoire of behaviors, and in many cases same-sex interactions actually involve only a subset of the full behavioral suite that is characteristic of the species.