A burning question for students of gay-ness

I was surfing for porn (oh, yeah, like you don't!) and I ran across this category: "gay bestiality."

What could this possibly mean? I'm imagining a man fucking a horse in the ass or a woman licking a dog's pussy.

Someone help me to understand this concept of "gay bestiality"!

I know what "gay" means when all of the participants are human, but in bestiality, does the concept of gayness apply at all?