Biological Exuberance: Animal Homosexuality and Natural Diversity

A word on terminology is in order. In this book, heterosexuality is defined as courtship, affectionate, sexual, pair-bonding, and/or parenting behaviors between animals of the opposite sex, while homosexuality is defined as these same activities when they occur between animals of the same sex. When applied to people, the terms homosexual, gay, or lesbian can refer either to a particular behavior when it occurs between two men or two women, or to an individual whose primary “identity” involves any or all of these activities. Since the notion of identity is inappropriate to ascribe to animals, these terms will be reserved for the behaviors that animals engage in and, where relevant, to describe individuals whose primary “orientation” is toward animals of the same sex where courtship, sexual, and/or pair-bonding activities are concerned. In addition, because the terms gay and lesbian have particularly human connotations, these will generally be avoided in favor of homosexual(ity) or same-sex (although it must be remembered that each of these words can have specific meanings independent of their human connotations when used in relation to animals, and they are employed as cover terms for widely divergent activities even among humans). When a particular individual engages in both homosexual and heterosexual activity, these words are limited to describing the animal’s specific behaviors (depending on the gender of the animal’s partner), while the animal itself is described as bisexual.⁵

Pirouette Dances, Ecstatic Displays, and Triumph Ceremonies: Courtship Patterns

To attract the attention and interest of a potential partner, animals often perform a series of stylized movements and behaviors prior to mating, sometimes in the form of a complex visual or vocal display. This is known as courtship behavior, and it usually indicates that one animal is advertising his or her presence to prospective mates or is sexually interested in another individual. If the interest is mutual, this may lead to mating or other sexual activity and possibly pair-bonding (for example, in birds). Some animals also use special courtship behaviors to conclude, as well as initiate, sexual activity, or to reinforce their pair-bonds. Courtship behavior is a common feature of homosexual interactions, occurring in nearly 40 percent of the mammals and birds in which same-sex activity has been observed.

Same-sex courtship assumes a dizzying array of forms, and zoologists often use evocative or colorful names as the technical terms to designate these most striking of animal behaviors (which are usually part of heterosexual interactions as well). Many species perform elaborate dances or kinetic displays, such as the “strutting” of female Sage Grouse, who spread their fanlike tails; or the spectacular acrobatics and plumage displays of Birds of Paradise and Superb Lyrebirds; or the courtship encounters of Cavies, who “rumba,” “rumble,” “rump,” and “rear” each other in an alliterative panoply of choreographed behaviors. In other cases, subtler poses, stylized postures, or movements are used, such as the foreleg kicking found in the courtship displays of many hoofed mammals; “rear-end flirtation” in male Nilgiri Langurs and Crested Black Macaques; ritual preening and bowing during courtship interactions in Penguins; “tilting” and “begging” postures in Black-billed Magpies; “jerking” by female Koalas; and “courtship feeding”—a ritual exchange of food gifts seen in same-sex (and opposite-sex) interactions among Antbirds, Black-headed and Laughing Gulls, Pukeko, and Eastern Bluebirds. Sometimes two courting individuals perform mutual or synchronized displays, such as the “triumph ceremonies” of male Greylag Geese and Black Swans; the “mutual ecstatic” and “dabbling” displays of Humboldt and King Penguins, respectively; synchronous aquatic spiraling in male Harbor Seals and Orcas; the elaborate “leapfrogging” and “Catherine wheel” courtship displays by groups of Manakins; and synchronized wing-stretching and head-bobbing in homosexual pairs of Galahs. Many birds have breathtaking aerial displays, including tandem flying in Griffon Vultures, shuttle displays and “dive-bombing” in Anna’s Hummingbirds, “hover-flying” in Black-billed Magpies, “song-dancing” in Greenshanks, and the “bumblebee flight” of Red Bishop Birds.

A male Superb Lyrebird (foreground) courting a younger male in the forests of Australia. He is singing and performing the dramatic “full-face display,” in which he fans his elaborate tail plumes forward over his head.