I’m a strong believer in sociobiology, in the idea that our everyday actions are motivated by our genes’ desire to reproduce themselves. But I’ve never considered the link between this genetic desire and what happens in our real lives to be a simple one to track. People perform actions every day and make many choices that would seem to decrease or even eliminate their potential to reproduce. (Consider, for example, the decision to wear leisure suits.)

Making love with the same sex would seem to fall into the category of the genetically unproductive and therefore biologically mystifying. Hence my question: Are we the only ones doing it? Every time I read an article in the popular press about the quest to isolate an explanation for human homosexuality this is a question I want answered. But not only is it never answered, it’s never asked.

Over the past year I’ve accumulated a number of stories showing that humans are not the only species engaging in same-sex mating. The stories I found were buried in scientific journals, not because the editors were trying to stifle the information but because they were trying to stifle yawns. It seems everyone among the knowledgeable readers of journals on animal behavior knows that animals engage in same-sex mating. It’s apparently so common it’s barely of interest. But it was news to me, and the stories I found in these articles covered a diverse range of sexual behavior.

Exhibit number one: the pigeon. “I always wanted to be someone who would mate for life, like pigeons and Catholics,” Woody Allen says in Play It Again, Sam. It’s true that pigeons tend to hang on to the same mate year after year, cooing and clucking and appearing to be fond of each other. But people who raise pigeons for homing and eating also know that males in captivity frequently mount other males. No one was sure whether this was some kind of aberration or whether it occurred in the wild as well until Hervey Brackbill, in a 1941 issue of an ornithological journal called the Auk, described watching two wild male birds taking turns crouching submissively and mounting each other. Like captive birds, wrote Brackbill, they “performed, to every appearance, normal copulation.”

Exhibit number two: the lesbian gulls. Like pigeons, standard operating procedure for seagulls is to form monogamous, heterosexual pair-bonds (scientists shrink from calling such things marriages) and then stick together until the death of one of the mates. But in 1979 a trio of ornithologists discovered that in three colonies of western ringbills, 1 to 2 percent of the gulls were female-female pairs. The girl gulls laid eggs and in some cases hatched and reared young just as the heterosexual couples did. In fact, 60 to 70 percent of the eggs were fertile, which also meant that some of the supposedly monogamous male gulls had to be straying from their mates. After further study the scientists stated that the phenomenon was widespread enough “not to be dismissed as a unique event peculiar to California, but rather seems an occurrence of evolutionary significance.”

Exhibit number three: the social-renegade snow goose. At Carver Park, Minnesota, during the summer of ’68, a pair-bond formed between a male Canada goose and a male snow goose. The snow goose actively pursued the Canada goose, keeping him away from other Canada geese. After several days the Canada goose accepted the snow goose, and the pair was formed. Though the Canada goose was much larger, he assumed the female role, following the snow goose and roosting close to him. The snow goose aggressively defended their territory. The pair stayed together from the middle of March until early May, when the snow goose was found dead of unknown causes.

Exhibit number four: Horicon Marsh. In a 1959 study at Horicon Marsh, which is a couple hours north of Chicago, biologists found that birds that didn’t pair with a member of the opposite sex often mated with the same sex. The researcher presented this as a case where the leftover birds settled for same-sex mates, but whether this was his assumption or a documented observation is unclear, as he didn’t state at what point during the mating season these birds selected same-sex mates. In any case, same-gender pairing occurred with both females and males.

The researcher also reported that during one season at Horicon a lonely male goose attached himself to the man who managed the marsh. The goose drove all the other geese away from the caretaker and hissed at visitors in an effort to keep them separated from him and his human mate. The goose was openly affectionate with the caretaker, frequently stretching out his neck and lowering his head coyly. In this posture, he addressed the caretaker with a prolonged snoring sound, a typical way geese display affection and attachment. How the caretaker responded was not recorded by the observer (scientists sometimes miss the obvious).

Exhibit number five: the anything-that-moves strategy. A friend of mine was slogging through a wetland in Lake County a few years ago, and when he emerged from the reeds and rushes he had a male bullfrog gripping the toe of his boot. The frog was attempting to copulate with his shoe and wasn’t in a hurry to give up. Despite the frog’s firm resolve, my friend claimed it was unsuccessful and no tadpoles were ever produced as a result of their union.

Exhibit number six: snakes in drag. Every spring male Canadian red-sided garter snakes congregate in groups of thousands while they wait for females to wake from hibernation and emerge from dens. When a female appears the males surround her, wrapping her in a “mating ball” that can contain anywhere from ten to a hundred guys. When scientists investigated the writhing sea of mating balls–clearly not a job for everyone–they were surprised to find that one out of six contained no female at all and that the males were all busy courting another male. The surrounded males turned out to have a female combination of pheremones rather than a male mix, and the other males responded to them as if they were actually females.

Exhibit number seven: transsexual fish. Some species have the ability to change gender at any point during their adult life.

Exhibit number eight: the langurs. Other primates– monkeys, chimps, and the like–frequently have sex with members of the same gender. They appear to do this for all kinds of reasons and at a variety of ages. In a 1990 study that must have been fascinating but was written up in such a technical way it’s hard to believe the subject could be sex, three scientists studied female-female mounting in a population of langurs, a kind of long-tailed monkey, in northwestern India. To make the authors’ dull story short, sex between females occurred frequently even though there were available males in the colony. According to the authors, this type of behavior has been described for a large number of vertebrate animals. And they write–almost as an aside, as though it’s common knowledge–that it has long been recognized that “such behavior is associated neither with structural abnormalities nor represents ‘sex reversals,’ but is instead considered a normal element in the behavioral repertoire” of everything with a spinal cord.

These cases can’t be simply explained. Each has its share of rational biological explanation and rampant mystery. A few of the reasonable explanations are: there may be an abundance of one gender or another; it may be advantageous to have sex with the same sex because then your competition isn’t so hot to trot with members of the opposite sex; mounting another animal may establish dominance; fooling other males into thinking you’re female may trick them into wasting precious mating time and energy with you, giving you an advantage when a real female comes along. Some of these things are probably true for some of the animals in question, but a whole lot of less pragmatic and harder-to-quantify things are also likely to be at work. For example, if male pigeons mount each other to establish dominance, why do they politely take turns?

Conventional wisdom, which claims that the purpose of living things is to reproduce the individual’s genes, might lead one to assume that same-gender sex wouldn’t occur. That clearly isn’t the case. These and other accounts suggest that any conceivable combination of sexual coupling that can be thought up is indulged in by some species or another at some time or another.