Understanding Aggressive Behavior in Animals

Aggressive behavior may be influenced by many factors, including:

Genetic predisposition. Some breeds have been selectively bred for protective behavior.

Insufficient social experience. A dog who had few opportunities to interact with other dogs and people as a puppy may overreact to strangers as an adult.

Maturity. Some dogs are quite friendly as puppies but begin displaying guarding, threatening, and other aggressive behaviors on reaching adulthood (between 2 and 3 years of age).

Unwitting encouragement from owners. Many people don't realize that if they try to soothe and reassure their dog when he gets belligerent, they're reinforcing the behavior. Other owners back off at any sign of aggression toward themselves, teaching the dog that he is in charge.

Territoriality. A dog may guard his bed, toys, food, house, yard, family members, car, and the street he regularly walks on. In a new environment he may react aggressively to anything approaching him and even to being looked at by another dog or a person.

Dominance. Aggressive behavior may arise during encounters with other dogs in an effort either to assert dominance or to resist being dominated. Similar status conflicts may also crop up between a dog and his human family members.

Roughhousing. Play fighting between puppies is normal and includes playful growling, chasing, nipping, poking, biting, and wrestling. All this fun helps puppies figure out their place in the pack. Older dogs enjoy play fighting, too; it's a way to bond and get exercise. But if a roughhousing person gets into the mix, aggression can escalate, particularly if the dog wins the match. Innocent rough play between person and puppy can develop into serious aggression as the dog matures.

Inability to escape. A dog who's cornered or tied up will react much more strongly to a perceived threat (such as a stranger approaching) than he would if he were free to move away.

Pain. If a dog is sore or has an injury, he may react aggressively if someone touches that part of his body. This is a reflexive response caused by pain.

Senility. Confusion or diminished senses (such as smell and sight) may interfere with an older dog's ability to recognize people, to anticipate being approached or handled, and to judge whether he's safe in a particular situation.

Predatory instincts.
Dogs are hunting animals. Most have an innate urge to chase anything moving away from them, whether it's a tennis ball or a delivery truck. Behaviorists don't classify hunting and chasing as aggressive behaviors unless they are directed toward people.