This article is from the Your New Puppy FAQ, by Cindy Tittle Moore with numerous contributions by others.
Courtesy of Joel Walton, jwalton@access.digex.net:
If you watch a litter of puppies playing, you will notice that they
spend much of their time biting and grabbing each other with their
mouths. This is normal puppy behavior. When you take a puppy from the
litter and into your home, the puppy will play bite and mouth you.
This is normal behavior, but needs to be modified so you and the puppy
will be happy.
The first thing to teach your new puppy is that human flesh is much
more sensitive than other puppies and that it really hurts us when
they bite. This is called bite inhibition. A puppy has very sharp
teeth and a weak jaw. This means that the puppy can cause you to be
uncomfortable when mouthing or puppy biting you, but can not cause
severe damage. An adult dog has duller teeth and a powerful jaw. This
means that an adult dog can cause significant damage when biting. ANY
DOG WILL BITE GIVEN THE RIGHT OR WRONG CIRCUMSTANCES ! If a small
child falls on your adult dog and sticks a finger in the dog's eye,
you should not be surprised if the dog bites. If you do a good job
teaching your puppy bite inhibition, you should get a grab and release
without damage. If you don't, you may get a hard bite with significant
damage.
It is simple to teach a puppy bite inhibition. Every time the puppy
touchs you with its teeth, say "OUCH!" in a harsh tone of voice. This
will probably not stop the puppy from mouthing, but over time should
result in softer and gentler puppy biting.
The commands necessary to teach a puppy NOT to mouth, are easy and
fun. Hold a small handful of the puppy's dry food, say "take it" in a
sweet tone of voice, and give the puppy one piece of food. Then close
the rest of the food in your hand and say "off" in that same sweet
tone of voice. When the puppy has not touched your hand for 3 to 5
seconds, say "take it" and give the puppy one piece of food. We are
teaching the puppy that "off" means not to touch. You should do this
with the puppy before every meal for at least 5 minutes.
After a couple of weeks of the above training, here is how you are
going to handle puppy biting or mouthing:
Unexpected mouthing (you don't know the puppy is going to mouth, until
you feel the puppy's teeth):
"OUCH!"
Expected mouthing (you see the puppy getting ready to mouth you):
You say "OFF" before the puppy can mouth you.
The puppy is mouthing you because of a desire to play.
You have to answer the question, "Do I have time to play with
the puppy now ?" If you do, then do "sit", "down", "stand" or
other positive 'lure and reward' training. If the answer is
"No, I don't have time for the puppy, right now." then you need
to do a time out (crate, or otherwise confine the puppy, so the
puppy can't continue to mouth you and get in trouble.
The above training methods have been modified from information that I
learned from Dr Ian Dunbar in his puppy training seminars and from his
excellent video 'Sirius Puppy Training' which is available by calling
510-658-8588.
 
Continue to: