ASPCA Logo

Aggression in Dogs

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.

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.