Cats and dogs and other domestic animals do it all the time, I used to have two female guinea pigs, they'd hump each other.
My older male cat tried to have love with one of our female cats awhile ago despite the fact that they both know they have been made surgically inert.
Our dog humps anything that moves, he even tries to hump one of our female cats who teases him like a whore, but then she beats him up and runs away
