Aggression in dogs can be a distressing problem for both the dogs and their owners. It is one of the most common reasons for dog owners to seek professional help.
What is aggression?
The Merriam-webster Dictionary defines aggression as:
- a forceful action or procedure (such as an unprovoked attack) especially when intended to dominate or master;
- the practice of making attacks or encroachments;
- injurious or destructive behaviour or outlook, especially when caused by frustration. It is important to understand that although most pet dogs are not a concern and will not bite people; under stress, many dogs have the potential to bite, and some can cause a great deal of damage.
It is important to understand that although most pet dogs are not a concern and will not bite people; under stress, many dogs have the potential to bite, and some can cause a great deal of damage.
There is an estimated 5000 dog bites in Ontario, Canada every year and over 500,000 nation wide with most injuries occurring in children 6 to 9 years old. It is estimated that there are 2 fatalities each year in Canada resulting from dog attacks.
What are the different types of dog aggression?
There are several different types of dog aggression including dominance aggression, defensive aggression (fear motivated aggression), predatory aggression, territorial aggression and possessive (resource guarding) aggression. Aggression can be due to resource guarding of a territory, an item, or a person; from fear or frustration; from pain; or from a high prey drive or high reactivity levels. The aggression can be directed at other animals or at people.
Dominance aggression
Dominance aggression is one of the most commonly occurring types of aggression in dogs.
Dogs are social animals and hierarchy in their pack or family is very important to them. Their hierarchy or position in the pack is determined by the outcomes of ongoing social challenges among group members. When one dogs’ hierarchy is higher than another, they will often assert dominance over the individual determined to be lower in the pecking order.
This often appears as aggressive to non-canine species but it is also a form of communication and not always a negative thing. The problem arises when individuals do not agree on their position in the pack or when a dog asserts his/her dominance on a human pack member.
Some common signs of dominant behaviour include resource guarding of their owner from other dogs or people, mounting dogs or humans, refusal to listen to their owners commands, growling when told to do something they don’t want to do, or refusal to give up their physical position, such as refusing to get off a couch when told to do so by their owner.
Defensive aggression (fear motivated aggression)
Defensive aggression (fear motivated aggression) is also known as avoidance morivated aggression and means to defend oneself with hostile or violent behaviour and this type of aggression encompasses three reactions; fight, flee and freeze. These three reactions are automatic defensive responses to a perceived threat and are hardwired into the brain.
Defensive behaviour when a dog is confronted with a perceived threat may present as growling, snapping or biting if the dog is unable to avoid or escape the situation. Generally, defensive aggression is not behaviour that occurs when presented with a real threat but when the dog perceives something to be a threat that is not, such as a child riding by on a bicycle.
A defensive aggressive dog will usually go through several predictable escalating behaviours prior to biting or attacking when in a stressful situation; anxiety (can include yawning, whining, drooling), avoidance (avoiding eye contact, turning head), escape (ie. hide under table, run from room), and freezing (body stiff, hackles up, staring). It is important to understand and be able to recognize the signs.
By learning about canine body language and being able to recognize your own dogs fearful and offensive postures, you can help to avoid and de-escalate situations prior to any bigger reactions such as growling and biting.
If you believe your dog suffers from fear motivated aggression, you are best to seek help from a canine behaviourist who can help guide your through the steps to best help you and your dog.
Predatory aggression
Predatory aggression is an instinct-based behaviour to pursue prey with intent to kill and possibly also eat the prey. Predatory aggression is usually seen as part of a sequence starting with an auditory or visual trigger. This is followed closely by a chase, capture and kill sequence.
All dogs have a prey drive however, some dogs have a prey drive that is much higher than other dogs. It is owners of these high drive dogs that tend to run into predatory aggression issues. Although labeled as aggressive behaviour, dogs that chase, hunt and kill other animals is actually an instinctual reaction and this does not necessarily mean that the dog is aggressive.
When directed properly, high prey drive dogs are extremely useful and highly obedient with their owners/handlers and are not at all aggressive with family members or others that they are not directed to “hunt”.
Dogs that generally have high prey drives are in herders and hounds groups. For example, terriers are well known for their high prey drives and are used as ratter dogs (vermin hunters). These dogs are often used to hunt and kill as many vermin as possible and are rewarded for their kills. Unfortunately, other small dogs and cats can become victims too.
Territorial aggression
Territorial aggression is defined as aggression directed toward perceived threats entering or approaching the dogs territory. Territorial dogs are often insecure and try to control who has access to their territory or home. Any unwanted visitor can be seen as a threat to their safety.
Territorial aggression in these situations does not include working guard dogs that are trained specifically to guard a property or territory against unwelcome visitors or intruders as well trained guard dogs are not insecure and they are operating under the instructions of their handler.

Dogs often exhibit some territorial behaviour with strangers when they have not been properly socialized and when they are rarely taken off their own property. Hence, it is strongly recommended that dogs are regularly taken off property for on leash walks in a variety of locations.
Possessive aggression or Resource guarding
Resource guarding is when a dog controls access to objects, food, people or locations that they deem as important. I believe that resource guarding can be one of the most dangerous behaviours as their bite is often quite severe instead of just a warning, and the aggression can be directed at any individual, including family members, unlike territorial aggression.
Behaviours present as warning signals such as staring, growling and snarling and can quickly escalate to overt aggressiveness such as full on bite or attack.
If you believe your dog is displaying signs of resource guarding, it is strongly recommended that you seek professional help from a behaviourist trained and experienced to work with this type of aggression.
What do I do if I think my dog is aggressive?
Most times, aggression issues in dogs can be treated and managed successfully. It is important to recognize that there is an issue and to figure out the triggers of the aggression.
Proper socialization and training is imperative for all dogs. Participating in group obedience classes can be very helpful. Getting your dog on a consistent on leash walking routine is also very important. If the issues persist don’t give up. Many aggression issues require behavioural modification techniques beyond the scope of most pet owners, so it is prudent to seek professional help.
Consult a canine behaviourist, or ask your veterinarian to refer you to one. Also get your veterinarian to check for physical causes of aggression such as pain and discomfort.
A Balancing Act 