I have two Jack Russell's, one male and one female. The male is 6 y/o and the female is 5 y/o. The female is very sweet natured, but loves to hunt for squirrels, rabbits and birds. These animals have always been intact whenever she has brought them to me. However, I came home tonight and found a headless squirrel in my bedroom. It appeared that she had chewed the head off and then vomited it up. Neither have ever done anything like this and I found it very disturbing. She went so crazy a couple of days ago chasing something small in my back yard, that she hit her tooth on a rock under my deck and knocked it completely out, root and all! Is this normal behavior for this breed?