The nightmarish vampire bat might not seem like a team player, given that it's a parasite and all, but in fact it demonstrates some pretty advanced social intelligence. It's in the best interest of a small animal like the bat to maintain a healthy and large community, and vampire bats, as it turns out, are capable of reciprocal altruism--basically, doing favors. Research by Gerald Wilkinson showed that bats share food (fine, they regurgitate blood. Happy?) with bats who are hungry, regardless of whether the hungry bats are close relatives. In fact, writes Boysen, "the bats seemed to keep track of who had shared with them in the past, and they were much more likely to reciprocate with those who had been generous to them on a previous occasion."