Biological Exuberance: Animal Homosexuality and Natural Diversity

Homosexual behavior occurs in more than 450 different kinds of animals worldwide, and is found in every major geographic region and every major animal group.⁴ It should come as no surprise, then, that animal homosexuality is not a single, uniform phenomenon. Whether one is discussing the forms it takes, its frequency, or its relationship to heterosexual activity, same-sex behavior in animals exhibits every conceivable variation. This chapter presents a broad overview of animal homosexuality and places it in the context of a number of other phenomena involving alternative genders and sexualities.

The Many Forms of Animal Homosexuality

For most people, “homosexuality” means one thing: sex. While it’s true that animals of the same gender often interact sexually with each other, this is only one aspect of same-sex expression. Animal homosexuality represents a vast and diverse range of activities: it is neither a monolithic nor an exclusively sexual phenomenon. This section offers a survey of the full range of homosexual activity found in the animal world, organized around five major behavioral categories: courtship, affection, sex, pair-bonding, and parenting. While these categories are not mutually exclusive and often blend imperceptibly into one another, they offer a useful introduction to the multiplicity of homosexual expression in the animal kingdom.

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.

Animals sometimes exploit specific spatial and environmental elements in their courtship activities as well. Special display courts are used in same-sex (and opposite-sex) interactions in many species, including the “drumming logs” of male Ruffed Grouse, the elaborate architectural creations of Regent Bowerbirds, and the traditional group or communal display areas known as leks found in animals as diverse as Kob antelopes, Long- tailed Hermit Hummingbirds, and Ruffs. In other species, dramatic chases that may cover great distances are part of same-sex interactions: aerial pursuits occur in Greenshanks, Golden Plovers, Bank Swallows, and Chaffinches; ground chases take place during courtships in Mule Deer, Cheetahs, Whiptail Wallabies, and Redshanks; aquatic pursuits occur in Australian Shelducks; while Black-billed Magpies combine both ground and aerial pursuit in their courtship behavior known as chase-hopping. Perhaps most amazing of all are the light-related displays of a number of bird species, which are designed to utilize specific properties of sunlight or other luminosity in the bird’s environment. Guianan Cock-of-the-Rock, for example, position their leks and courtship displays in special “light environments” that maximize the visibility of the birds through a sophisticated interaction of the ambient light, the reflectance and coloration of the bird’s own (brilliant orange) plumage, and the forest geometry in which they are located. Anna’s Hummingbirds precisely orient the trajectory of their stunning aerial climbs and dives to face into the sun, thereby showing off their iridescent plumage to its best. As a male swoops toward the object of his attentions (either male or female), he resembles a brilliant glowing ember that grows in intensity as he gets closer. To advertise their presence on the lek, male Buff-breasted Sandpipers perform a wing-raising display that exploits the midnight sun of their arctic habitat. Seen from a distance, the brilliant white underwings of each bird flash momentarily against the dull tundra background, reflecting the weak late-night sunlight and thereby creating a luminous semaphore that attracts other birds, both male and female, to their territories.⁶

In addition to spectacular visual displays, homosexual courtship—like the corresponding heterosexual behaviors—can involve a veritable cacophony of different sounds. Female Kob antelopes whistle, male Gorillas pant, female Rufous Rat Kangaroos growl, male Blackbuck antelopes bark, female Koalas bellow, male Ocellated Antbirds carol, female Squirrel Monkeys purr, and male Lions moan and hum. The “snap-hiss” ceremonial calls of Black- crowned Night Herons, the croaking of male Moose, “geckering” and “snirking” of female Red Foxes, the chirp- squeaks of male West Indian Manatees, “yip-purr” calls of Hammerheads, the yelping and babble-singing of Black- billed Magpies, “lip-smacking” in several Macaque species, the humming call of Pukeko, “stutters” and “chirps” of male Cheetahs, the “vacuum-slurping” of male Caribou, and pulsive scream-calls in Bowhead Whales are just some of the vocalizations heard during same-sex courtship and related interactions. Sometimes pairs of birds execute synchronized vocal displays, as in the duets of rolling calls performed by Greylag gander pairs, or the precisely syncopated “moo” calling of pairs of male Calfbirds. In a few cases, courtship activities involve nonvocal sounds or sounds produced in unusual ways. Male Guianan Cock-of-the-Rock, Ruffed Grouse, Victoria’s Riflebirds, and Red