Animal corpses disappear if you damage them. Did your last explosive arrow fly into a bear corpse? The bear has a fairly long death animation.It evaporated so I can only assume it is dead. They should die when I shoot them in the head with an exploding arrow. I used to hunt dire wolves and zombie bears for the leather. Then they started dropping red bags so people began to hunt them for the red bags. I think this is why they evaporate now.