Dog Aggression: What is it how do we recognize it?

Very often we are told, or we decide that a particular dog is “aggressive”, but do we really know what that means?

Aggression can be defined as actions which are assumed to be motivated by:

Fear or frustration.
A desire to exert fear or frustration over others
A desire to exert dominance over others.
Aggression is a naturally occurring phenomenon that has various sources. Understanding the source of the aggression can help us deal with it. Some of the sources of aggression include:

Maternal Aggression

This occurs when a mother dog either attacks or threatens a perceived threat to her litter (ie. If you get too close to the puppies). This type of aggression only occurs in the early rearing period of the litter.

Frustration Induced Aggression

In almost all animals (humans included), frustration will lead to aggression. Often frustration occurs as a result of confusion.

Defense Aggression

This is the response to a direct threat and will occur at the exact moment of the threat. The dog has three options when faced with a threat: freeze, flight or fight. Often we as dog owners take away the options of freeze or flight, leaving fight (or aggression) as the only option.

Pain Induced Aggression

This is caused by physical pain felt by the aggressing dog. It may be a response to illness or injury.

Territorial Aggression

This is very common in un-neutered males. These dogs will defend their right to the territory, even across species boundaries.

Dominance Aggression

This type of aggression typical occurs between males, but can also happen between two females and a male and a female dog. The aim of this aggression is to claim status over another individual. It can also occur when a dog challenges an owner or trainer.

Displaced Aggression

Sometimes when an animal is threatened by another, more dominant animal, it aggresses toward a third, less dominant animal. Most dog owners will see this when walking their multiple dogs. A dog behind a fence barks, causing one of their dogs to aggress towards one of their other dogs.

Learned Aggression

This occurs when an act of aggression is rewarded in some way. It may be that the act of aggression got the dog a reward (Fido growled at you and you gave him the snack you were holding), or it resulted in a threat going away (Fido snarled and barked at the postman and he ran away).

So, how do we tell when our dog is about to aggress? Well, there are many signs, but they happen so quickly that we often don’t see them. Look out for the following:


Your dog’s hair will stand on end. This also happens when they are excited, so don’t take this in isolation! This makes your dog look bigger, thereby being more threatening to the perceived threat.

Tail Wag

This is a different wag to the loose, happy wide wag. This tail wag will be stiff and narrow.


Ears will be back against the head.


Pupils will be dilated (ie, lots of black) and you may see a half-moon of white at the sides.


The mouth will be pursed, with the sides forward.

It is important to note that a lot of these signals are shared with (good) excitement, so remember to look for the big picture – a number of these signs together to give you a clue as to whether your dog is going to aggress.

In dealing with aggression, remember your body language. You may not realize that you are telling your dog you are submissive. Check out last month’s article to brush up on body language. Train, train, train your dog. By assuming the role of trainer you reinforce your dominant position. Also, it may be possible, with training, to desensitize your dog to the aggression causing stimulus. Sometimes pharmacological intervention is needed. Your vet, together with a trained behaviourist, will be able to advise if this is the best course of action for your dog. Male dogs that show evidence of aggression must be neutered. Often this solves the problem, as the dog now has no need to show his dominance. Lastly – avoid provocative situations. If you know your dog does not like other male dogs – don’t take him into a situation where he cannot avoid other male dogs!!