Respiratory. A pit clamps on, you take a shovel or rake handle, slide it into its collar and twist however you must to choke the dog. As it asphyxiates, the jaws will unlock.
This is an ancient thread, what brought you here?
But if asphyxiation prompts the dog to release, then the jaws are not *locked*.
Therefore, what biological mechanism unlocks the jaws?
An American Staffordshire terrier is a member of canis familiaris.
What biological mechanism of canis familiaris enables it to lock its jaws? Can you point to this biological mechanism in a German shepherd, rottweiler or Akita?
As to the date of the thread, I didn’t notice.