Biological Exuberance: Animal Homosexuality and Natural Diversity

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 Bishop Birds, for example, make distinctive whistling, drumming, or clapping sounds by beating or fanning their wings (which in some cases have specially modified, sound-producing feathers), while male Anna’s Hummingbirds produce a shrill popping sound as a result of air passing through their tail feathers during display flights. Some of the most extraordinary sounds during same-sex courtship are made by aquatic animals: Walruses generate eerily metallic “bell” sounds by striking special throat pouches with their flippers and castanet-like “knocks” by chattering their teeth, while Musk Ducks have an entire repertoire of courtship splashing sounds made by kicking their feet during displays variously named the paddle-kick, plonk-kick, and whistle-kick. Finally, some Dolphins appear to engage in a sort of sonic “foreplay”: male Atlantic Spotted Dolphins have been observed stimulating their partner’s genitals with pulsed sound waves, using a type of vocalization known as a genital buzz.