dog

Question
quick question my family has a great blue heeler. incredibly smart he knows sit, lay, stay, roll over, sit pretty bow, crawl, turns left or right on command, fetches, and  backs up. just so you know how smart he is but, every time a another dog in family or cat gets by me he will lay down between me and the dog or cat and growl never attacking at all or biting the other animal but what's that about?

Answer
He is being protective apparently. It is a natural instinct. If it becomes a problem you will have quite a bit of work to deal with the problem since it appears he is already set in his ways. As long as he does not become overly aggressive I wouldn't worry about it. You can tell him no and thump him slightly on the nose. That may deter him.