Why Are So Many Animals Homosexual?

Few creatures can boast of devotions so deep as greylag geese. Most are monogamous; many spend their decade-long adult lives with the same goose, side-by-side in constant communication, taking another partner only if the first should die. It’s a remarkable degree of fidelity, and it includes relationships of a sort that some humans consider unnatural.

Quite a few greylags, you see, are gay. As many as 20 percent by some accounts. That number might be high: It includes those males who first take a male partner but later pair with a female, or whose first bond is with a female, but after she dies, takes up