Dog Aggression

Apr 25, 2018

Aggressive behaviour such as growling, snapping, physically attacking, and biting is a concerning behaviour problem for many dog caregivers. Aggression is a natural behaviour for dogs, which arises most often as a response to situations in which the dog feels vulnerable or fearful. It can occur in any breed of dog. Helping dogs overcome patterns of aggressive behaviour can be challenging, requiring expertise, hard work, caution and patience.

Attempting to tackle this problem without the help of a knowledgeable veterinarian and/or board-certified behaviourist is not recommended. There are many misleading sources of information on the treatment of aggression available online and from other sources. While most cases of aggression can be treated or managed safely, establishing a realistic prognosis and timeline for treatment is essential. It is crucial to take precautions to manage dogs with aggressive behaviour safely to protect other members of your community. Inappropriate treatment can worsen aggressive behaviour and ultimately increase the risk to the dog’s caregivers or community.


The veterinarian will obtain a detailed history and will do a thorough medical examination to check for possible medical causes of aggression, such as pain and neurological conditions. Blood tests or further diagnostics may be recommended.


Aggression is a natural behaviour in dogs, used mainly for defence. There can be many emotional motivations for aggressive behaviour towards humans, but fear is the most common by far. Dogs may learn to use aggression more over time because it can be an effective tool for making scary people or other animals back off.

Other less common emotional motivations for aggressive behaviour in dogs include: resource guarding (also based in fear), territoriality, inappropriate play, and redirected, impulsive, and predatory behaviour.

Note, most canine behaviour experts agree that dominance (a desire to attain a higher social rank) is not a motivational factor for canine aggression towards humans. Unfortunately, dominance theory is now deeply embedded in dog training culture and many trainers or lay people still recommend outdated training techniques such as alpha rolls and punishment-based training methods to ‘correct’ non-existent dominance problems.

Aggressive behaviour can occur in dogs of either sex, at any age. However, intact males approaching two years of age are overrepresented for unruly behaviour or active aggression problems. 

Treatment may include:

  1. Initially, avoiding situations that would trigger aggressive behaviour.
  2. Canine body language education for caregivers, so they can recognize early signs that the dog is uncomfortable and know to remove a dog from those triggering situations before aggression begins.
  3. Avoidance of punishment-based training methods such as shock, prong, and choke collars, which have been shown to increase aggressive and fear-based behaviours over time.
  4. Use of rewards-based and confidence building training. Building a relationship of trust and understanding between dog and owner.
  5. Use of desensitization and counter-conditioning training programs (with qualified professional help only) to change the dog’s emotional reaction to triggers.
  6. Use of anxiety reducing medications. This can be a helpful adjunct to behavioural modification treatment plans. Medication alone is usually not helpful for treatment of these problems.


Prevention is obviously preferable over treatment for aggression. Since most aggressive behaviour in dogs occurs out of fear, training and interactions with people and other animals should be designed to build trust and confidence. Never force your dog into an environment or interaction in which they are uncomfortable.

We recommend using only force-free, rewards-based training for dogs. Avoid working with any trainer who recommends using compulsive or punishment-based training methods such as shock, pinch, or choke collars.

If you get your dog as a puppy, you have an opportunity to prevent behaviour problems through socialization during their socialization period (six to 16 weeks).

Regular veterinary checkups and vaccinations are important for your puppy’s health. These can often be made an enjoyable experience be feeding high-value treats throughout the exam.


Canine aggression is a complex behaviour problem and treatment with a qualified profession is highly recommended. It is not simply an obedience problem requiring more training. Misinformation about the causes and treatment options for aggression is common, and inappropriate ‘training’ can worsen the behaviour.

Your veterinarian, or a board-certified veterinary behaviourist is best suited to diagnose and treat behaviour problems or they may refer you to a qualified professional. Taking care of your dog’s mental health is just as important as taking care of their physical health.

Dr. Kathleen Cavanagh, BSc DVM MET
Consulting Online Editor CVMA

Dr. Karen van Haaften, DVM
Consulting Behaviour Editor                                                      

April 16, 2018