Dog anatomy: do some dogs have locking jaws?

Straight up I can assure you no. No no no. This is a myth that has gotten way out of hand and used to demonise certain types or breeds of dog, and to try to justify breed specific legislation.

This is a picture of a dog skull. No, I don’t know the breed, but it doesn’t matter. They all look basically the same. There is no mechanism in which the closed jaw bone can lock.

Dog jaws are hinged, so they can only open up and down, whereas humans have a side-to-side motion for chewing. The hinged jaw is not designed to chew, rather to allow a dog hold prey and then go about breaking it into smaller chunks to eat. The dog needs to be able to move fast, potentially opening and closing the jaws frequently to reposition the hold.

The jaw is just a piece of bone. The power of a bite hold comes from the surrounding muscles (temporal & masseter). When you bite down you can feel these muscles on the sides of your head, the temporal from behind your ears forward near the eyes, and the masseter in front of your ear lobes and down. Ours are very small. In dogs, these muscles are in a similar position, over the top of the head and down the sides, and much larger and stronger than ours. These serve the anatomical purpose for eating, to break up food, since they cannot chew.

Yes, in some breeds you can visibly see these muscles working and theoretically this means they have a stronger hold, though this is still not any kind of locking mechanism. Note too, that bite force is not directly related to how defined the jaw muscles might appear.

So please, if you hear anyone talking about dogs with locking jaws, set them right respectfully. Some people just don’t know and have real fears. Some people are set in their ways. Explain that there is simply no physical evidence this exists, and no anatomical advantage to it.

Call me, I can help!

Bonus info: Hardly any digestion happens in a dog’s mouth, as they don’t (can’t) chew, and saliva is largely for lubrication purposes only. The stomach is designed to accommodate large chunks and much more acidic than ours to break those chunks down. It’s also why our dogs sometimes regurgitate food – the stomach says that chunk is too big, and then the dog can have another go. Gross but normal.

Photo credit: unknown, sourced from the Internets.