Aggressive behaviour

Every dog, and every breed of dog, is capable of showing aggression. It's just that some are more likely to show it than others. It can reveal itself in growling, snarling, baring teeth, barking, lunging, snapping, biting, a stiffly wagging tail or raised hair (hackles) along the back. While most of these are obvious in their intent, others can be quite unclear and contradictory, so take all behaviour signs into account to establish the type of aggression you may be seeing, as well as the possible cause.

The type of aggression your dog is displaying will depend on the situation. There are times when we really don't know why it's happening, but in most cases the reason is one or more of the following.

Resource-guarding or possessive aggression
Your dog has something they don't want to share, be it food, a bone, toy, or even their favourite bed. Fear aggression This is an attempt by a dog to stop a fearful thing from getting closer to and affecting them – a stranger, another dog or sometimes the vet.

Inter-dog aggression
This is aggression directed at other dogs, both known or unfamiliar. Irritable aggression shown by dogs when they're in pain or unwell. Most commonly displayed by older dogs

Territorial/protective aggression
A dog being aggressive from behind a fence is being protective of its patch. Some do it when walking on a leash – they're being protective of their owner.

Play aggression
Two dogs enjoying a bit of rough play. With this form of aggression they usually keep themselves in check without it escalating.

As with people, there can be a lot of different catalysts behind a dog's aggressive behaviour. Correct diagnosis is the starting point to management, treatment and re-training. Here are some common underlying reasons.

Poor social skills
A puppy that misses out on early formative social experiences can become aggressive when they're older. But as a dog gets older, it still needs regular, fun exposure to different people and dogs so it continues to refine its social skills.

Bad past experiences
A negative experience in a dog's past can make them aggressive in that situation in the future. For example, if a pup was attacked by a small white dog, it might grow up to become aggressive to all white dogs.

Generalisation
Sometimes a single bad experience can snowball and become applied to many different future situations. For instance, the pup attacked by the small white dog may grow up to project this experience onto all small white dogs, and then to all white dogs, and then to all dogs, and so on.

Individual temperament
Some dogs have a genetic basis to their aggression. A parent may have been aggressive and passed this trait on. This may not become evident until the dog is older.

A trigger situation
How a dog feels about being in a certain situation can determine whether they react to it aggressively. For example, at the vet clinic.

Aggression is a serious problem. And an incorrect diagnosis can make the problem worse. Contact your local veterinarian or a veterinary behaviourist.