Dog Aggression

Understanding Dog Aggression Causes and Types of Aggression

Aggression in Dogs

Aggression, defined as an appropriate or inappropriate threat or challenge that is ultimately resolved by combat or submission, is one of the most common behavioral problems in companion dogs.

Aggression can occur in any breed, age or gender of dog and can be directed towards people or other animals. It is potentially very destructive, and very dangerous. Aggression can take a number of forms and be caused by a number of things.

Common signs include biting, growling, snarling, curling lips, barking, snapping, head and tail up with direct stare, head and tail down with body withdrawn, frantic tail waving, posturing and lunging.

Common Causes of Dog Aggression

All breeds, ages and genders of dogs can become aggressive. However, very few dogs are born aggressive, and frequently aggressive behavior in dogs is normally a direct result of something else.

Aggression in dogs is part of the normal range of canine behavior in many cases and is strongly influenced by breed, sex, early socialization, handling, individual temperament, genetics and other variables.

It is possible for underlying medical conditions to cause or contribute to aggression, although this is rare. Still, medical causes of aggression (such as pain or neurological disorders) must be ruled out before an appropriate treatment protocol can begin.

Breed Susceptibility

When humans started breeding companion dogs, they did so in a manner that would consistently produce desired traits. The current range of canine breeds is a direct result of human manipulation and breeding for these various traits.

Some breeds were bred to be pampered, gentle and tolerant. Other breeds were bred to protect flocks or herds, or for family protection. Some breeds were bred for their ability to track and hunt birds, wild boar, rats or fox. Others were bred for size, or smallness, or coat, or cuteness.

Dogs bred for aggression (which they never should have been), may naturally have a tendency to be aggressive. Most breeds commonly associated with aggression towards people (“pit bulls,” bull dogs, others) actually were bred to be extremely trainable and restrainable by people, but were taught to be aggressive to other animals.

Behavioral Causes

No matter how gentle a puppy is, abuse, mistreatment and neglect can cause that dog to suffer behavioral problems, including aggression. Dogs that are raised without proper socialization, nutrition and affection will not know how to act appropriately in social situations involving people and/or other dogs. It is extremely sad to see fear or other forms of aggression in a dog because of an abusive or neglectful background.

Medical Causes

Medical causes of canine aggression are uncommon but may include: pain, head trauma, swelling of the brain, rabies, distemper, epilepsy, arthritis and other neurological or painful disorders. Painful dogs may bite their owners without really knowing what they are doing (for example, after being hit by a car or attacked by another dog).

Curbing Aggressive Behavior

Aggressive behavioral problems are difficult to resolve without the assistance of a specialized trainer or veterinary behaviorist. Realistically, dog owners should hope to manage and modify unacceptably aggressive behaviors in their pets, without expecting complete correction. Of course, the younger the dog, the better chance there is to resolve inappropriate behaviors.

The goals of treating canine aggression are to eliminate the aggressive behaviors and render the dog safer, to enhance human safety and the human-animal bond, to alleviate the anxiety causing the dog’s aggressive behavior and to make the dog and its people happier and calmer.

Treatment for aggression involves desensitizing the dog to the eliciting stimulus (other dogs, threatening people, children approaching their food, etc.) and counter-conditioning or rewarding the dog for calm or good behavior. Complete control over the dog, by either the owner or the trainer, is essential for this to work.

A head halter or harness can be a valuable tool that provides not only physical control but also causes the dog to focus his attention on his handler, rather than on external stimuli. No amount of superficial advice can provide what your veterinary behavioral specialist can provide to assess and address your dog’s particular situation.

However, physical punishment and harsh restraint are strongly discouraged as they usually intensify aggression-based behaviors.

Proper socialization of puppies to people and to other dogs is critical, regardless of the dog’s breed, gender or prospective use. Puppies go through major developmental phases between 3 and 12 weeks of age where proper and positive interaction with other animals, people and novel environments are crucial to helping them develop appropriately solid social character traits.

Puppy classes are an excellent way to achieve this socialization while establishing a solid training foundation. If an owner fails to capitalize on these critical developmental periods, their puppy may not develop the proper skills and behaviors to make it a good household member.


Understanding the cause of canine aggression is essential to assessing and helping a dog and its owner in any given situation. Professional help from a veterinarian and a skilled behavior expert are key components of a healthy recipe for treating aggression in our companion dogs.

While this condition can be extremely frustrating for owners (and no doubt for affected animals as well), there are steps that can be taken to address the situation. Euthanasia should never be an automatic “treatment” or “solution” for behavioral disorders in our pets.

Types of Dog Aggression

Types of Aggression in Dogs

There are at least five commonly encountered forms or subtypes of canine aggression. It is important to determine the type of aggression a dog is displaying before attempting to address the problem. In most cases, owners should seek the advice of a professional trainer to diagnose and address aggression in their dogs.

Fear Aggression

Fear aggression, or defensive aggression, happens when a dog perceives that it is in a threatening situation. The fearful reaction may be entirely normal and appropriate under the circumstances, or it may approach being phobic.

There is no age or gender predisposition for this form of aggression, although it is often seen in young puppies around 12 weeks of age, and again when they approach sexual maturity between 9 and 12 months of age.

Fear aggression is not affected by neutering. Certain breeds seem to have a genetic predisposition to this behavioral condition, particularly German shepherds, Border collies and several other breeds. When put in an unfamiliar and threatening situation, a dog’s instincts are to run or to fight.

Depending upon the situation, the only realistic option may be aggression. For example, fear aggression is highly overrepresented in dogs that are chained. Fear aggression can be extremely dangerous because it can lead to human harm.

Signs of fear aggression include trembling, growling, barking, lip-lifting, snapping, cowering, crouching, backing up, lip-licking and tail tucking. Often, so-called “fear biters” have a history of abuse, and lash out when cornered.

Impulse-Control (“Dominance” or “Social Status”) Aggression

Dominance aggression in dogs can occur in all breeds and either gender. It is reported to be more common in English springer spaniels and Dalmatians in the United States. The clinical signs involve growling, baring teeth, staring, a dominant and forward stance, and/or biting – particularly in response to people staring, reaching towards or over the dog or punishing it inappropriately.

This type of aggression is often displayed toward human household members, such as reaching for the pet, pushing it off sleeping sites or approaching food or toys.

Interdog Aggression (Male or Female)

Interdog aggression is almost always exhibited between dogs of the same sex. It seems to be more common between intact male or female dogs. The signs are intense staring, hair raising, growling and challenges, although frequently once a fight starts, the dogs are almost silent. It is an “old wives tale” that male-male dog fights are worse than those between two females.

In fact, males challenging one another with this type of aggression usually fight until one of them submits. In fights between females, the fights can lead to extremely severe injuries, and death. Interdog aggression becomes dangerous to people only when they try to break up the fight, as the involved dogs are fighting irrespective of pain tolerance. These fights are often described as involving “blind rage.”

Territorial/Protection Aggression

This type of canine aggression is characterized by barking, growling, snarling, biting and other aggressive behaviors apparently designed to protect objects (car, house, property, people). It worsens when the dog is behind discrete boundaries, such as in a car or behind a fence. I most cases, these dogs are not aggressive away from their territory.

Food-Related Aggression

Food aggression is characterized by growling and lip-lifting if approached, or sometimes even if only looked at, when eating. It often progresses to biting if removal of the food or treat is attempted. Obviously, this can be quite dangerous to people, especially children who are oblivious to the dog’s verbal and postural warnings.

Resolving or Preventing Canine Aggression

Most dogs are not born aggressive. While some breeds are particularly trainable to a number of behaviors, including aggressive ones, they usually do not come by aggressiveness on their own.

Much more often, aggressive dogs have been mistreated, ignored, chained, unsocialized or improperly trained during critical periods of development. Humane training methods under the guidance of a skilled trainer can help nip aggressive behaviors in the bud. Head halters and harnesses are very helpful in controlling dominant dogs.

Consistency, kindness and predictability in managing aggression is critical. Methods that involve extreme punishment or harsh forms of physical restraint have no place in modern dog training and actually can make dogs more aggressive and dangerous to the people in their world. Many talented, knowledgeable canine behavior experts are available to help you and your veterinarian address aggression in your dog.

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