Mouthing behavior is very common in puppies, especially at 4 months (teething) and 7 months (when molars come in). It’s normal canine play behavior and how they explore their world. Some breeds are simply very oral. In adolescent dogs, however, mouthing can become attention-seeking behavior, especially once the dog learns it works!
Do not use physical punishment. It might work for you, but it would be at the expense of your relationship with the dog. With some dogs, it can even encourage some dogs to get worse.
When dealing with a mouthy puppy, use a pathetic yelp! In many cases this will cause the puppy to stop biting/mouthing and start kissing you. Now, withdraw your attention. Praise the pup for an appropriate response and redirect his attention to something safe. Make sure to do this every single time.
In adolescents, your response will be similar. Give a pained, “Ow!” and then immediately withdraw your attention. You can even leave the room to stress your point. Redirect the dog’s attention and praise every single time.
To avoid problems with mouthing, do not roughhouse with the dog. Teach and encourage, “This is how we play.”
Tug-of-War Rules. You’ll hear many people say, “Never play Tug-of-War with a dog.” But you can play the game safely if you follow the rules:
Use one designated toy only.
Take breaks and work on self-control – Stop, Sit and so on.
If any teeth touch your skin, for any reason (even if it’s accidental), drop the toy. The game is over.
Always remember, to stop unwanted behavior, you’ve got to stop rewarding it. The dog wants attention and to a dog, any attention – even negative attention – can be its own reward.