RE: IDNR Snakes/Cats ?
I have seen a bobcat 10 yardsfrom my stand...
As for Mountain Lions young males are known to roam to find a territory. It is likely a few find their way across the missisippi via bridges every year looking for territory. Unknown whether any females are in the state so a population can get started. If you do see one you can shoot it as it is considered a nonnative species.
As for snakes...no reason to release them. Plenty of copperheads, timber rattlers insouthern IL.