Every single category within the animal kingdom features species who regularly exhibit homosexual behavior: vertebrates and invertebrates; amphibians, birds, fish, mammals, and reptiles; even insects!
We do know that animals can experience pleasure. Think about stroking a cat under its chin or getting the good spot right behind a dog’s ear.
But do they experience pleasure from all interactions? Say, carnal ones? Humans are known to derive pleasure from sex, but do animals?