I'm going to disagree with another comment that says it is dominance. The dominance theory has been disproven as the original study was skewed and dogs are not wolves and dogs understand that we are not dogs. read more
And I was told, that any living thing that crossed his path he killed, and he killed cats & rabbits while on his leash. So, yes, some dogs do. Puppy had mistaken the chic for a toy. And the Pitbull was trained for it. But dogs genuinely really don't kill any living thing. They really don't. read more
While I do agree that small dogs and cats can be indoor animals, big dogs (the kind that kill) shouldn't be around anything they can kill. A dog in a yard or in the street, needs to be on a leash; so many attacks can be prevented if people listened to that. read more