Homosexual encounter. Female Laysan albatrosses on the Hawaiian island of Oahu pair off with other females. (Image: Tui De Roy/Minden Pictures/FLPA)

Gallery: Nature’s homosexual pin-ups

Editorial: Homosexuality in nature is no guide to morality

NOT long ago, the news was full of reports about two male Humboldt penguins at a zoo in Germany that adopted an egg, hatched it and reared the chick together. It seems like every time you turn around, the media spotlight has fallen on another example of same-sex liaisons in the animal kingdom.

In the past few years, the ubiquity of such behaviour has become apparent. This summer evolutionary biologists Marlene Zuk and Nathan Bailey from the University of California, Riverside, published a paper on the subject that included examples from dozens of species ranging from dung flies and woodpeckers to bison and macaques.

That is just the beginning of the story. The burning question is why same-sex behaviour would evolve at all when it runs counter to evolutionary principles. But does it? In fact there are many good reasons for same-sex sexual behaviour. What’s more, Zuk and Bailey suggest that in a species where it is common, it is an important driving force in evolution.

Although terms such as homosexual, gay and transgender are commonly used by the mass media, and even by some ethologists, Bailey and Zuk believe you shouldn’t extend these descriptors of human sexuality to animals. “It’s not simply that they are burdened with the weight of social, moral and political implications, which can obscure objective scientific study,” says Bailey. “The problem is that while we can observe the sexual behaviour of …