You must be wary of obtaining a puppy from a breeder who has taken a puppy away from his mother too soon, because it not only deprives the puppy of important lessons but can also affect the puppy's future health. For example, the puppy obtains antibodies to many diseases by feeding from his mother. Every sip of milk is like a vaccine that protects the puppy for many weeks after he leaves the litter and is placed in his new home.
Between 3 to 7 weeks of age, the mother teaches her puppies basic doggy manners. She communicates to the puppies what's acceptable and what's unacceptable behavior. For instance, after the puppies' teeth have come in, nursing them has become a painful experience, so she teaches them to take it easy. She does whatever it takes, from growling, snarling, and even snapping, and she continues this lesson throughout the weaning process when she wants the puppies to leave her alone. After just a few repetitions, the puppies get the message and respond to a mere look or a curled lip from the mother. The puppy learns dog language - or lip reading, as we call it - and bite inhibition, an important lesson.
The puppies also learn from each other. While playing, tempers may flare because one puppy likes to bite another one too hard. The puppies discover from these exchanges what it feels like to be bitten and, at the same time, to inhibit biting during play. Puppies that haven't had these lessons may find it difficult to accept discipline while growing up.
Puppies separated from their canine family before they've had the opportunity for these experiences tend to the identify more with humans than with other dogs. To simplify, they don't know they're dogs, and they tend to have their own sets of problems, such as the following:
- Aggression toward other dogs
- Difficulty with house training
- A dislike of being left alone
- Excessive barking
- Mouthing and biting their owner
- An unhealthy attachment to humans
This is an excerpt from Dog Training for Dummies