In the past, the saying "the birds and the bees" generally meant only one thing—sex between a male and female.
But, actually, some same-sex birds do do it. So do beetles, sheep, fruit bats, dolphins, and orangutans. Zoologists are discovering that homosexual and bisexual activity is not unknown within the animal kingdom.
Roy and Silo, two male chinstrap penguins at New York's Central Park Zoo have been inseparable for six years now. They display classic pair-bonding behaviour – entwining of necks, mutual preening, flipper flapping, and the rest. They also have sex, while ignoring potential female mates.
Wild birds exhibit similar behaviour. There are male ostriches that only court their own gender, and pairs of male flamingos that mate, build nests, and even raise foster chicks.
National Geographic filmmakers caught female Japanese macaques engaged in intimate acts which, if observed in humans, would be in the X-rated category.
"The homosexual behaviour that goes on is completely baffling and intriguing," says National Geographic Ultimate Explorer correspondent, Mireya Mayor. "You would have thought females that want to be mated, especially over their fertile period, would be seeking out males."
Well, perhaps, in a roundabout way, they are seeking males, suggests primatologist Amy Parish.
She argues that female macaques may enhance their social position through homosexual intimacy which in turn influences breeding success. Parish says, "Taking something that's non-reproductive, like mounting another female—if it leads to control of a resource or acquisition of a resource or a good alliance partner, that could directly impact your reproductive success."
On the other hand, they could just be enjoying themselves, suggests Paul Vasey, animal behavior professor at the University of Lethbridge, Alberta, Canada. "They're engaging in the behavior because it's gratifying sexually or it's sexually pleasurable," he says. "They just like it. It doesn't have any sort of adaptive payoff."
Matthew Grober, biology professor at Georgia State University, agrees, saying, "If [sex] wasn't fun, we wouldn't have any kids around. So I think that maybe Japanese macaques have taken the fun aspect of sex and really run with it."
The bonobo, an African ape closely related to humans, has an even bigger sexual appetite. Studies suggest 75 percent of bonobo sex is non-reproductive and that nearly all bonobos are bisexual. Frans de Waal, author o fBonobo: The Forgotten Ape, calls the species a "make love, not war" primate. He believes bonobos use sex to resolve conflicts between individuals.
Other animals appear to go through a homosexual phase before they become fully mature. For instance, male dolphin calves often form temporary sexual partnerships, which scientists believe help to establish lifelong bonds. Such sexual behaviour has been documented only relatively recently. Zoologists have been accused of skirting round the subject for fear of stepping into a political minefield.
"There was a lot of hiding of what was going on, I think, because people were maybe afraid that they would get into trouble by talking about it," notes de Waal.
Whether it's a good idea or not, it's hard not make comparisons between humans and other animals, especially primates. The fact that homosexuality does, after all, exist in the natural world is bound to enter any debates on the topic.