People say that, John, but I'm not sure it really makes sense. A well fed cat will still kill mice. In fact, animals seem to rarely apply the notion of 'reason' to their motivations. If they kill, it is because something inside them drives them to that, and that something can have any number of complex physiological driving mechanisms. Humans are no different from other animals in this.
I think it's hard to compare humans to other animals because our perspective on humans is so familiar and intimate and our perspective on other animals is so fundamentally divorced from their inner lives. It's a lot like noticing that I'm different from everyone else in the world because I'm the only one whose thoughts are audible.