Bisexual Species: Unorthodox Sex in the Animal Kingdom
Homosexual behavior is common in nature, and it plays an important role in survival
By Emily V. Driscoll
Two penguins native to Antarctica met one spring day in 1998 in a tank at the Central Park Zoo in midtown Manhattan. They perched atop stones and took turns diving in and out of the clear water below. They entwined necks, called to each other and mated. They then built a nest together to prepare for an egg. But no egg was forthcoming: Roy and Silo were both male.
Robert Gramzay, a keeper at the zoo, watched the chinstrap penguin pair roll a rock into their nest and sit on it, according to newspaper reports. Gramzay found an egg from another pair of penguins that was having difficulty hatching it and slipped it into Roy and Silo’s nest. Roy and Silo took turns warming the egg with their blubbery underbellies until, after 34 days, a female chick pecked her way into the world. Roy and Silo kept the gray, fuzzy chick warm and regurgitated food into her tiny black beak.
Like most animal species, penguins tend to pair with the opposite sex, for the obvious reason. But researchers are finding that same-sex couplings are surprisingly widespread in the animal kingdom. Roy and Silo belong to one of as many as 1,500 species of wild and captive animals that have been observed engaging in homosexual activity. Researchers have seen such same-sex goings-on in both male and female, old and young, and social and solitary creatures and on branches of the evolutionary tree ranging from insects to mammals.
Unlike most humans, however, individual animals generally cannot be classified as gay or straight: an animal that engages in a same-sex flirtation or partnership does not necessarily shun heterosexual encounters. Rather many species seem to have ingrained homosexual tendencies that are a regular part of their society. That is, there are probably no strictly gay critters, just bisexual ones. “Animals don’t do sexual identity. They just do sex,” says sociologist Eric Anderson of the University of Bath in England.
Nevertheless, the study of homosexual activity in diverse species may elucidate the evolutionary origins of such behavior. Researchers are now revealing, for example, that animals may engage in same-sex couplings to diffuse social tensions, to better protect their young or to maintain fecundity when opposite-sex partners are unavailable—or simply because it is fun. These observations suggest to some that bisexuality is a natural state among animals, perhaps Homo sapiens included, despite the sexual-orientation boundaries most people take for granted. “[In humans] the categories of gay and straight are socially constructed,” Anderson says.