Training her was brutal. They are the most "anxious to kill" dogs I've ever seen. It's sport for them. Finally one day it clicked and she now knows not to kill. She just grips on a large animal like a clamp. She can get under a sheep or cow and nip at their belly to keep them at a run and match their pace stride for stride.
If my wife does not come to bed with me but comes in an hour later, that dog will not allow her in the room until I say it's ok. She guards my kids the same way. (my poor wife!)
That picture you posted looks just like my dog. The teeth are not quite as plentiful though.
Remind me to call ahead if you ever invite me by for a visit...
Good puppy! But they don't always have to show their teeth to get their point across.