They could be road kills. Alot of guys stop and pick up road kills for the horns. They pick up the body, cut the horns off and dump the body in a secluded spot. A deputy game warden out my way used to do this too. He would keep the roads clean of the carcasses and got a hell of a collection of racks for his effort. I don't know if he had permission for this, but he's dead now so it doesn't matter.