Agonistic: Personality conflict between two dogs without another cause.

Barrier Frustration: A barrier (for example, the dog is tied up) causes frustration. The dog can't escape, so it attacks when someone enters his or her territory.

Competitive: Housemate dogs who fight, usually over social status or human attention.

Displaced: The aggressive intent was redi6rected from one target to another.

Dominance aggression: The dog mistakenly thinks he runs the house and reacts to a conflict situation with a person by turning aggressive.

Drug-induced: While on certain medications, a dog's perceptions may be affected and cause aggression.

Encephalopathic: Aggression caused by a medical condition in the brain (for example, epilepsy).

Fear-induced aggression: A dog that growls or snaps when afraid thinks he is fighting for his life. Because of a combination of genetic tendencies, early experience, lack of socialization and sometimes abuse, a dog with this type of aggression that cannot escape when cornered will attack. During the growling, snapping or attack, the dog shows fear postures such as crouching with its tail between its legs.

Food guarding: The dog has the mistaken idea that people take food instead of give it. This causes them to feel threatened any time someone comes near his or her food.

Improper socialization: The dog may have been isolated as a puppy and socially stunted, causing aggression towards situations they are unfamiliar with.

Intra-sex: Female dogs who fight only female dogs, or male dogs who fight only male dogs.

Irritable: This type of aggression is due to a medical problem that lowers a dog's aggression threshold.

Pack response: Dogs act differently when in a group. Some may show aggression when in a group.

Pain-induced: This is a reflex aggression designed to relieve pain and protect the animal.

Play escalation: Some aggression starts as play such as roughhousing, and may escalate to aggression.

Possessive Aggression: associated with possessing toys or stolen non-food objects.

Territorial: The dog may display aggression in conjunction with inappropriate guarding of an area, such as the owner's home.

Trained: Some dogs are trained to bite people and may become confused and mistakenly show aggression or bite a person when not instructed to.

Unintentionally learned: Some people pet an aggressive dog to try to calm the dog. This action is understood by the pet as positive reinforcement or praise of the aggressive behavior so the behavior continues.

The first step when noticing any aggressive behavior is to contact your veterinarian. The earlier the intervention the more likely the behavior can be managed. Your veterinarian can work with you to determine the cause of your pet's aggression and recommend appropriate treatment and/or training.