ASPCA logo Aggression is the most common and most serious behavior problem in dogs. It’s also the number-one reason why pet parents seek professional help from behaviorists, trainers and veterinarians.

Top 12 Behavioral Problems in Dogs

What Is Aggression?

The term “aggression” refers to a wide variety of behaviors that occur for a multitude of reasons in various circumstances. Virtually all wild animals are aggressive when guarding their territories, defending their offspring and protecting themselves. Species that live in groups, including people and dogs, also use aggression and the threat of aggression to keep the peace and to negotiate social interactions.

To say that a dog is “aggressive” can mean a whole host of things. Aggression encompasses a range of behaviors that usually begins with warnings and can culminate in an attack. Dogs may abort their efforts at any point during an aggressive encounter. A dog that shows aggression to people usually exhibits some part of the following sequence of increasingly intense behaviors:

Becoming very still and rigid
Guttural bark that sounds threatening
Lunging forward or charging at the person with no contact
Mouthing, as though to move or control the person, without applying significant pressure
“Muzzle punch” (the dog literally punches the person with her nose)
Growl
Showing teeth
Snarl (a combination of growling and showing teeth)
Snap
Quick nip that leaves no mark
Quick bite that tears the skin
Bite with enough pressure to cause a bruise
Bite that causes puncture wounds
Repeated bites in rapid succession
Bite and shake

Dogs don’t always follow this sequence, and they often do several of the behaviors above simultaneously. Many times, pet parents don’t recognize the warning signs before a bite, so they perceive their dogs as suddenly flying off the handle. However, that’s rarely the case. It can be just milliseconds between a warning and a bite, but dogs rarely bite without giving some type of warning beforehand.

Classification of Aggressive Behavior

If your dog has been aggressive in the past or you suspect she could become aggressive, take time to evaluate the situations that have upset her. Who bore the brunt of her aggression? When and where did it happen? What else was going on at the time? What had just happened or was about to happen to your dog? What seemed to stop her aggression? Learning the answers to these questions can clarify the circumstances that trigger your dog’s aggressive reaction and provide insight into the reasons for her behavior. You need an accurate diagnosis before you can hope to help your dog.

Aggressive behavior problems in dogs can be classified in different ways. A beneficial scheme for understanding why your dog is aggressive is based on the function or purpose of the aggression. If you think of aggression this way, you can determine what motivates your dog to behave aggressively and identify what she hopes to gain from her behavior.