Young puppies up to the age of six months will sometimes act aggressively and even snap at or bite someone. These beginning signs of aggression are usually easy to correct because of the pup’s age, size, and lack of maturity.

Young dogs, six to ten months old, represent a different quality and degree of aggression but are still considered manageable and, through reconditioning, can be corrected.

A dog older than ten months, who is acting aggressively and has bitten someone, is much more difficult to recondition, and the aggressive behavior can sometimes not be changed.

No matter what solution one tries, there is no guarantee that a mature dog who has already bitten someone will never bite again. You have a potentially very dangerous situation on your hands!

The body language or signs of defensive aggression displayed by a puppy are: a prolonged direct stare, raised hackles, growling, showing his teeth, arching his body, and curling his tail between his legs. If any of these signs are present during the following circumstances, you should be concerned and need to get professional help:
 

• eating
• sleeping and suddenly disturbed
• being petted, especially when your hand is drawn over the top of his head
• approached by strangers
• approached by other dogs
• protecting toys
• protecting the house or yard
• being groomed or examined
• being around children
   

Any dog who is not trained, that is, does not understand his subordinate position to you, will try to become "top dog." One example of this is when a dog repeatedly jumps up on you. An out of control dog is like a belligerent teenager, always pushing to test the boundaries. This behavior can be a prelude to aggressive behavior.

Assert your dominance! Get your dog trained! Teach him to respect you and others near and dear to you. If you are concerned about your dog’s aggressiveness, seek the guidance of a professional dog trainer. In the meantime, confine or muzzle your dog whenever people are present.