Its not the animals that are worried about consent, its us. Well, at least most of us...but we don't count rapists' views on sex for the same reason we don't count a thief's view on property rights, or a member of the KKK on minority rights. I still seriously doubt that the animals find it funny to be fucked by a human. Having an unwanted cock shoved in you is never a positive event, no matter what retarded mental gymnastics you might perform to spin it as such.