It sounds to me like these may not be poached animals, but possibly animals that after the season were dumped there because the hunters (I'll use that term loosely for now) either didn't want to, or didn't know how to properly butcher and dispose of the carcass. They probably thought to dump them somewhere that coyotes and crows would find them but not in a place where many humans would be offended.

However I would give your local warden a call and let him know what you found. If they were poached, it will leak out. Criminals are notorious for letting out their secrets.