When a pet bites, the first step is to get a veterinary exam with diagnostic tests to rule out any health problems. The next step is to work with a behaviorist.

Beware of simple answers. Any combination of factors may be triggering aggression, including fence-fighting, displaced aggression, dominance, drug side-effects, other pets, pain triggers, predation, possessiveness, fear, hormonal changes, protection of young, pack response, play, protection of home or family, neurological abnormalities, improper socialization, and intentionally and accidentally trained behaviors.

Once a pet has bitten someone, it's more likely the behavior will be repeated. If the bite broke the skin or there were repeated bites, the prognosis is even grimmer. Getting professional help right away is essential.

(Animal behavior experts Susan and Dr. Rolan Tripp are the authors of "On Good Behavior." For more information, visit their Web site at AnimalBehavior.net.)

Animal behavior experts Susan and Rolan Tripp are the authors of "On Good Behavior." For more information, visit their Web site at AnimalBehavior.net.