Rock Mystery

While hunting in Albemarle county last weekend, I ran into a minor mystery. Throughout the whole wooded area (around 1000 acres) we were hunting in we kept finding rocks that had been turned over. Now I know that bears like to turn over and pull apart logs for the grubs that are in them but I have never read about them doing it to rocks. There was only one other hunter on the farm and he was in another area. It was a random pattern and I couldn't see where anything had been disturbed other than the rock itself. Most of the rocks were of such a size as to rule out all animals except man and bears. I'll be going back to hunt again in early November during the muzzle loading season and maybe I can "dig" up an answer for this mystery.