The first thing to make clear is that no dogs 'lock their jaws'. All dogs hold their jaws closed by actively clenching their muscles and there is no mechanism to freeze their jaws in that position. If a dog is holding into something, they can choose to release it at any time. What differs is the strength with which a dog can bite down, and his or her inclination to bite and hold on rather than bite and release. Some dogs such as pit bulls, mastiffs and Rottweilers have short muzzles and large jaw muscles that are well attached to the skull. Dogs differ in their inclination to bite and they way they bite, and genetics can play a role here.
Border collies were developed to herd and are more inclined to nip quickly with just their front teeth. Dogs bred for proficiency in large game hunting or fighting may be more inclined to bite and hold on, sometimes shaking their head. This type of bite is used to suffocate and incapacitate prey. With all dogs specific breeding and training is very important in determining how likely a dog is to bite and to hold.
Border collies were developed to herd and are more inclined to nip quickly with just their front teeth. Dogs bred for proficiency in large game hunting or fighting may be more inclined to bite and hold on, sometimes shaking their head. This type of bite is used to suffocate and incapacitate prey. With all dogs specific breeding and training is very important in determining how likely a dog is to bite and to hold.
