By far the most common form of aggression in dogs is driven by fear.
The dog perceives something or someone as threatening and they try to defend themselves. Even if the dog is not defending themselves but something they regard their own - food, toys, territory, people - there can be a component of fear behind the dog's aggressive behaviour.
Fear-aggression is an instinctive survival behaviour and should be respected.
Fear cannot be overcome with force. Trying to scold your dog for aggressive behaviour will make things worse.
Your dog needs help, not punishment.
Never respond to aggression with aggression
If You're Aggressive, Your Dog Will Be Too, Says Veterinary Study, University of Pennsylvania
If aggression has only a mild fear component, it may be relatively straight-forward to treat. Other forms of fear-aggression require a lengthy desensitisation and counter conditioning program.
It can be difficult to determine if aggressive behaviour is caused by fear or not. A qualified behaviourist or dog trainer will be able to help you.
Aggression that is not promoted by fear is often directed at other dogs, for example inappropriate play skills, bullying or compulsive fighting.
Some dogs simply do not know how to appropriately interact with other dogs while some have an urge to be aggressive towards other dogs. The reasons can be related to genetics, lack of socialisation or both.
Don't let your dog bully other dogs
Compulsive fighting (gameness) has been selected for in some breeds by humans. However, this does not automatically mean that certain breeds are more dangerous than others. Genetics is just one of many components that influence the development of an organism. It cannot predict if a dog will turn into a particularly aggressive individual.
The Real Pit Bull, non-profit organization focussed on educating the public about pit bulls and dispel common myths about this breed
Breed Specific Legislation is not supported by the Australian Veterinary Association (AVA):
"Legislation to prevent dog bites and to manage aggressive dogs should focus on the individual dog and the owner not the breed. Breed-specific legislation for dog bite prevention has failed to reduce the frequency of dog bites both in Australia and overseas."
Read more at: Breed-specific legislation by the Australian Veterinary Association (AVA)
Predatory aggression - aggression which is directed at a potential prey item - is in a category of it's own. This type of aggression is best prevented through management.
Even before a dog starts growling, snarling, snapping or biting, there are usually warning signs which precede aggression.
Back off if you notice the early signs of aggression. Teach your children how to recognize the signs and, more importantly, know how to keep your children and dogs safe. Also check out Dog Safety for Kids by Doggone Safe and How Kids Should Not Interact with Dogs by Dr Sophia Yin.
Freeze: The dog becomes stiff and stops moving. For example if the dog is consuming food, they stop eating and get ready to defend their food.
Hard Eye: The dog stares either directly or from an angle at the perceived threat or target. For example if the dog is guarding their food, toys or resting place, they may stare from an oblique angle at someone approaching them.
Curled Lips: The dog raises their upper lip, sometimes exposing the front teeth (canines). For example the dog is resting and someone reaches out to touch them.
More advanced and obvious warning signs are growling, snarling and snapping. If the threat or trigger does not go away, the dog may then bite.
Some dogs do not have the full repertoire of threat signals and may escalate faster, e.g. go from curled lips to a bite or even bite without any warning at all.
This is why we never punish threat signals. They are very valuable indicators of the dog's possible intentions.
First manage the situation, then start a behaviour modification treatment to address the underlying fear.
The first important step is to manage the situation so the dog is never exposed to the triggers that may cause them to become aggressive. For example, if your dog is aggressive towards strangers, keep strangers away from your dog.
The dog may have to be fitted with a muzzle to prevent accidents and make everyone involved in the treatment program feel more at ease. There is nothing wrong with muzzles, they are simply a safety tool. Learn more about muzzles at this excellent muzzle advocacy site:
The next step is to start a systematic program to resolve the dog's fears which are at the root of the aggressive behaviour.
Go to the section on 'Fearful Dogs' to learn more.
Managing the situation is always the first step. With some aggression cases it may be the only step while other cases may be suitable for a behaviour modification program.
Always keep everybody safe, including the dog by preventing the triggers that cause the aggression. For example if your dog lunges, growls and snaps on leash at other dogs*, keep a far enough distance from other dogs so your dog does not react.
Dog Reacts to Trigger
Move Away Before Dog Reacts
* Note that this type of aggression could also be fear-related.
If your dog's behaviour can be modified depends on various factors, for example if the dog has ever bitten and how bad the damage was or how committed you are to manage and work with your dog.
Sometimes management is the only option which means the dog has to be kept away from his triggers for the rest of their lives. For example if your dog attacks and seriously injures another dog at the dog park, you can never take your dog to a dog park again.
As with fear-aggression, fitting a muzzle might be a good idea to prevent accidents. Check out this website to learn more about muzzles and why they are a very valuable but underused tool.
Help yourself and your dog to have a less stressful life. Talk to a qualified behaviourist or dog trainer to find solutions for your aggressive dog.
Signs of Aggression, by Doggone Safe, a website dedicated to dog bite prevention through education
I'm Not a Monster, website dispelling myths about certain breeds. Excellent info on dog bite prevention, how to greet a dog, dogs and kids and more (with posters).
Care for Reactive Dogs, website dedicated to helping reactive dogs
Teaching Your Dog to Wear a Muzzle, YouTube video by Chirag Patel