On this topic, you might want to do a medline search for Ann Perkins, and
Ed Price. Ann did some work with homosexual rams at the United States
Sheep Research Station, with some interesting results.
On this general topic, I find it hard to beleive that people will accept a
biological basis for gay animals, yet not one for humans. In horse
breeders, for instance, if there is the rare event of twins, with one of
both sexes, the male is killed. Lore has it that he will never breed.
Rodent studies have it that his brain was too feminized, hence it would be
a gay stud! Or so I was told in a lecture on this topic.
This may be reversed with regards to the sex of the killed, as I am
working from memory, not any notes.