Puppies bite. Puppy biting and mouthing is natural. Since they do not have hands and opposing thumbs they use their mouths to play and investigate.
When you observe a litter of puppies there is a lot of mouthing going on. When pup bites too hard, his littermates yelp and stop playing with him. The pup quickly learns that when he bites too hard, his buddies wont play with him, so he chooses to use a softer mouth on them. This is called Bite Inhibition and is an important lesson for the pup.
Forbidding a young puppy from biting altogether may offer immediate and temporary relief, but it is potentially dangerous because your puppy will not learn that his jaws can inflict pain. Puppy must be taught to inhibit the force of his bites (Ian Dunbar)
That cute little nibble will not be cute anymore once the puppy has grown into an adult. They need to learn this before they are four months old.
Teach your puppy to trust you this is necessary to tech your puppy about bite inhibition.
NEVER hit, slap or shout at the puppy, physical punishment will lose that trust. It will not stop the puppy from biting it will only scare and confuse him.
Make sure you are not reinforcing his biting behaviour. Grabbing the mouth and shouting at him is actually reinforcing him by giving him attention being that negative attention.
We need to teach puppy that while mouthing is ok he must stop when asked to , mouthing should only be initiated by you. We must teach puppy that he must not hurt you and he must know that he must not exert pressure at all when biting.
If your puppy is biting/ mouthing with pressure you must simply say “ouch” and turn away from him for 5 seconds and pretend to be licking your wounds, then return to the pup and say gently. This will teach the pup what his mother and littermates would have done and he will realise that when he bites his fun to goes away. The severity of the “ouch” must match the severity of the bite
If your pup acknowledges your "ouch" and stops biting, praise him and lure him to offer a different behaviour and offer him a yummy treat. If your pup ignores the "ouch" and continues biting, yelp "Owwwww!" and leave the room. Your puppy has lost his playmate. Return after a minute timeout and make up by lure-rewarding your puppy to come, sit, lie down, and calm down, before resuming play.
If puppy gets aroused by the ouch sound and has not decreased his biting after 3 attempts in a row, END your play session and try again later on in the day.
Even once your pup's biting no longer hurts, pretend that it does. Greet harder nips with a yelp of pseudo-pain. Your puppy will soon get the idea that humans are super sensitive.
The pressure of your puppy's bites will progressively decrease. Once your pup exerts NO pressure when mouthing, only then, teach him to reduce the frequency of his mouthing. Teach your pup that mouthing is ok until you request him to stop. Give him the command ”leave”
Each time your pup stops mouthing reward him and begin playing again. Remember to give clear indication to your pup when your play/training session has ended. “All done”
Be persistent and consistent.
Reference: Dr Ian Dunbars Good little dog book (page 96-100)