Puppies bite a lot, and one major reason is that they are teething until they are about 10 months old or so. Another is that they are learning about the world through their mouths. Their teeth are extremely sharp but fortunately the strength in their jaws is not what it will be later. When a puppy stays with its mother and littermates for a good amount of time (at least a couple of months from birth), it will get feedback from them that its bites hurt. The other animals may yelp and/or move away.
These behaviors are ones we can modify and use ourselves, as we train puppies not to bite. Give a startled shriek when a puppy bites, nips, or mouths you — even if it didn’t really hurt. Move away from the pup and ignore it for a short while. It will learn, though not necessarily as fast as you would like it to.
Puppies may be more likely to mouth or bite children, and here you have to juggle several things.
First, you absolutely do not want any child to be bitten badly by any dog. This happens a lot, and can lead to a lot of fear, pain, and even disfigurement in the children. Lawsuits and euthanasia of the dog are other unpleasant possibilities. Young children should always be watched around any dog.
(My dog and I once lived for a month with friends while my husband was away, and all the adults in the house were extremely vigilant about LarryDog’s access to their toddler.)
Second, as the dog and the children grow up, you will be able to loosen the restrictions, but do it with a lot of thought.
If you have any doubt about a dog of yours, consider muzzling it when it’s out walking with you or when you have company. I’ve used muzzles and have found that dogs get used to them. If you train a dog to accept a muzzle by offering very yummy treats (small pieces of hot dog, for example) through the muzzle when the dog is hungry, it won’t take long for the dog to wag its tails when it sees the muzzle.
There is plenty more to say on this topic, but I will leave it at that for now, with just one more thought: if you have a puppy or adult dog that is biting and you don’t really know why, do have a good veterinary exam, including the inside of its mouth. There could be a physical reason.
A great resource for teaching a puppy to inhibit its bite is Ian Dunbar’s DVD, Sirius Puppy Training.
You can see my review of Sirius Puppy Training here.