All this means is kill animals that are called out by another animal. If you are going for the achievement for killing 15 predators that jumped on you then you can get this too. At the end of the game there will be a Lion that calls in my Lions. Just keep killing the lions he spawns and you should get 10 pretty fast. So if you see a Hyena up on a rock howling, don't kill it. Instead, shoot the ones that come out to attack.