Baby carnivores have to be taught to kill by their parents. The parent will bring a live prey
animal to the baby carnivore, which "plays" with it's prey, until it learns to kill and eat it.
Playing with prey is actually learning to kill, and thus to eat and survive. Domestic cats and dogs
mimic this behavior, without which no carnivore would eat.

kb

>  bring it back as a 'trophy', many times not. A coworker recently
>  described how his (fully grown, not a kitten) cat was torturing a baby
>  field mouse for a while until he saved the mouse from the cat. At first
>  he thought the cat would just kill the mouse and didn't want to interfere
>  with his instincts. But after a while it became obvious that the cat
>  knew what to do, but just preferred batting the poor thing endlessly,
>  like some toy. (This cat has actually killed wild life before, from mice
>  to rats to birds, so is aware of how to do it).