aggression: rats

Question
QUESTION: my rats show their rowdy sides a lot, but is it normal for one of the litter mates to bite its owner for no reason? all you'd have to do is put your hand to their level and he will attack it. what  can i do to keep this from happening again?

ANSWER: Normal for all rats, no, but normal for a territorial rat - sure. He may be cage aggressive or food aggressive, having it develop more over time. Does he do this outside the cage at all?

---------- FOLLOW-UP ----------

QUESTION: no. but my mom thinks it is him being jealous or protecting his brother.and my dad said that to just slightly tap his nose and say firmly "no" and that should stop him.is this true?

Answer
Rats don't generally take to that sort of training like dogs or cats do - instead, they see it as you challenging them and it can actually make it much worse. I've had little success trying to train using negative reinforcement at all. Instead, approach with treats, so that he associates you with good things. If he does this while he's out of his cage, immediately put him away, playtime over. If he only does it while inside his cage, and if you offer him a treat and he avoids the treat to bite you, remove the treat and leave him be. Eventually he'll figure out he gets further when he doesn't bite than when he does.