I read a very interesting book on animal sexual behavior called Biological Exuberance. I had no idea that animals use sexual behavior in so many non-reproductive ways--bonding, dominance, affection, rape. I'm an urban person and I don't have many opportunities to watch lesbian ducks mount each other. (As one of my LJ friends had, in her childhood--she was surprised by my surprise!) The book was published in 1999, so this stuff isn't new--the biologist who wrote it seems to have basically sacrificed his scientific career to do it.

I read the book for a piece of fan fiction, which you can read here because I think I haven't put it on AO3 yet. I have the characters argue about the question of whether animal sexual behavior is part of GLBT studies.