It ain't my show, but I wouldn't necessarily include Opossums, nor skunks. Nor beaver, bunnies, squirrels, gophers, pdogs, wood/pack rats, etc.
Most tolks tender "predator hunting" to game that can be called. You can call bears, lions, wolves, bobs, lynx, coyote, fox, badgers, and coons. I'd suppose weasel types like a fisher would come in, maybe, heck if I know, we don't really have them to speak of in KS - I reckon wolverines would come in too, but I've never seen them on a predator contest.
So, I suppose the question is more towards - is it a predator calling contest, or a furbearing contest. My cousin and I have a trapline full of skunks that could add up REAL QUICK