Man of Honour
But are there any documented incidences of animals being exclusively homosexual, or are they all simply animals being hormonal in the absence of an available or receptive female?
Can't be bothered to use my brain for you right now, sorry: http://en.wikipedia.org/wiki/Homosexual_behavior_in_animals
Oh, and:
An estimated one-quarter of all black swans pairings are homosexual and they steal nests, or form temporary threesomes with females to obtain eggs, driving away the female after she lays the eggs. [31][32] More of their cygnets survive to adulthood than those of different-sex pairs, possibly due to their superior ability to defend large portions of land. The same reasoning has been applied to male flamingo pairs raising chicks. [33] [34]
So in answer to Castiel, yes, there are.