Do wild animals play? Of course they do, especially mammals! Yes,much of their time is spent looking for food and survival, but there are definitely times when they are not hungry and they probably find themselves bored from time to time. So, why does it surprise you that they might kill another animal for fun. Animals are not these robots that just behave out of instincts. There is a lot of current research that is showing that animal psychology is much more complex than we originally thought. Duhh!! Any pet owner should be able to figure that one out. Personally, I think most researchers are starting out with the wrong null hypothesis. They begin with the assumption that animals only act out of instinct and then design experiment to see if they cane prove that hypothesis wrong. I think they should start with the hypothesis that animals are exactly like humans and then design experiments to see how they are different from humans. Have you read "Dragons of Eden" by Carl Sagan? It's a good read. He suggests that the separation between animals and humans is not that big, and that it is a continuum. In other words, psychologically, we have everything animals have + a little more. And because emotions are generally associated with the more primative parts of our brain, which all mammals also have, it it suggests that all mammals have these emotions. I've had pet for a long time, and it does not take a rocket scientist to know that this is true!