Sexes: Leapin' Lizards!

Lesbian reptiles act like males

Readers of science journals know a good deal about bisexual aphids, "homosexual" gulls, and "transvestite" fish, species in which the male adopts the coloration and movements of the female to trick other males. Some researchers argue that every expression of human sexuality has some sort of analogue in the animal world. But even jaded followers of animal sex studies will have to admit that a Harvard team has now discovered something really new: "lesbian" lizards that copulate like males.

So far biologists have identified 27 kinds of parthenogenetic lizards—all-female species that lay eggs to produce exact genetic copies of the mother. On field trips in Arizona and Colorado, a team of researchers headed by Psychobiologist David Crews found that four of these species engage in mock male-female sex.

An active female mounts a passive one, curves the tail under the other's body, strokes the partner's back and neck, joins genital regions, and rides on top for one to five minutes. The active female lizard always has small undeveloped eggs, while the passive female has large pre-ovulatory eggs. But there are cyclic variations in behavior and egg size in these reptiles, and roles reverse; the passive female of one encounter can be the active partner of the next. Says Crews: "We are now trying to determine whether this malelike behavior facilitates reproductive function." Translation: the psychobiologist does not yet know why the females mock the male-female behavior of related two-sex species. The eggs hatch with or without the lesbian courtship.

Crews thinks the discovery has important implications. "What we have found here," he says, "is the first evidence of animals where sex and sexuality are independent of each other." Still, it is too early to announce that sex for its own sake was first discovered by lizards. The mounting behavior may serve to synchronize the egg laying, or increase the number of eggs. Or it may be, according to Crews, that the malelike behavior among the female lizards is a kind of "compensation" for life without males. Or it might be an evolutionary hangover from the good old male-female days. Since stories about animal sexuality are inevitably drawn into human sexual politics these days, Crews may be called to task by radical lesbians for his hetero chauvinism. If so, he will have to plead guilty: his team is currently treating eggs with hormones in hopes of producing the species' first males.