Ah, i used to be able to say that about Bernie, nobody can get that tug off him, without 'give' command being given. Id take it to the beach, so he'd be mouthing the tug, not other peoples dogs as a youngster. But no dog could get it off him.
Till we got a bitch.
Now she just snarls at him, and he drops the tug immediately. Like he instinctively knows, that YES, she may well be willing to take 'it' a little further. He backs down. Draws the line at suicide clearly.