There is ONE actually (all the others that appear to act 'gay' will prefer to fuck a female when they have the opportunity). They all have mating seasons and are 'triggered' by estrus - it's why dogs will try to hump anything to remove the urge if no female is available when estrus is in the air, ditto other animals, they cannot reason, they don't feel attraction like we do, they are essentially programmed just to procreate and if the urge is upon them and no female is available, a male, a human leg, or anything to take away the urge will be used. Even the Professor who studied the Bonobo said we should beware of assuming apparent homosexual acts are the same as we think of it (and he was gay!) but of course people used that as evidence animals also have 'gay' members when they absolutely do not. EXCEPT ONE 'species'....

Domesticated sheep that act 'gay' are the ONLY ones who have been observed to STILL choose their own sex to attempt to copulate with even when there is a female available for them. They theorize it might have something to do with the antibiotics or hormones they get fed, but there doesn't appear to be any real studies to find out why. Fits the narrative better to pretend homosexuality is a real thing in the animal kingdom