older dog and new puppy

Question
My son brought home a puppy that he saw thrown out of a car. This was a week ago. We have a dog (Rat terrier) that is 4 years old. He shies away from her and want eat anywhere near her. How long do you think it will take for him to accept her?

Answer
It could take a long time.  He is old enough he may have lost interest in puppy biting games.  More likely so, if he hasn't been around many puppies.  I just realized my friend's dog that I am so pleased with how well he does as a 6 year old, has been visiting us and our puppies all his life.  Having done without puppies for 4 years, yours may be slow to accept one.  If he wants left alone, I would support him.  As she matures, and is less puppy like, he may accept her more and more.  It is unusual for an older male and female not to get along.  Be sure he gets plenty of attention.