What Causes Aggressive Behavior in Dogs?

by | Feb 3, 2022 | General Information

We all want dogs that enjoy walks and playtime. We want to take them anywhere and introduce them to anyone. But a dog’s aggressive behavior can stop that dream in its tracks. 

Definitions of dog aggression vary, but generally, it is “the threat of harm to another individual involving snarling, growling, snapping, biting, barking or lunging.” Growling, barking, showing teeth, and staring are warnings of physically harmful behaviors that may follow.

The initial step in dealing with a dog’s aggressive behavior is understanding the causes. In this first two-part blog post, we will look at many causes of dog aggression. Next month, in Part 2, we’ll talk about dog aggression training and other ways to stop this unwanted behavior.

The Problem and Consequences of Dog Aggression

A dog’s aggressive behavior is dangerous. The dog can hurt and be hurt by others trying to defend themselves. 

Liability

With teeth designed to grab and tear meat, even a small dog’s bite can cause serious injury. And you, the dog parent, will be held responsible. Currently, 36 states have strict liability laws addressing dog bites. For example, in some states, you will be liable for your dog injuring a person or property whether or not you knew that your dog could be aggressive.

A Loss of Enjoyment

You can’t take an aggressive dog to many places. The dog park is out of the question, and friends and relatives won’t want them in their homes. Neighbors may avoid you and your dog. Even feeding time can be difficult if the dog is food aggressive. 

Lowering the Chances for Adoption

Many shelter dogs act aggressively because of abuse or neglect in their past. As shelters do not have the time or staff to engage in extensive training, these dogs may be labeled unadoptable. As a result, they will linger in the shelters, and some will be euthanized.

Now let’s look at what causes aggression. Where does it come from?

Happy dog

Health and Biology

Injury and Illness

The first thing to check is a possible medical problem. An injured or sick dog may become aggressive because the condition makes them vulnerable, which is why they may be protecting themselves. Some illnesses, such as rabies, affect the brain and cause aggression, among other symptoms.

Aging

Your senior dog may begin to show some signs of aggression. They’ve developed chronic aches and pains, tire more easily, and don’t have the patience they used to. They may start losing their hearing or sight or may become confused. It can make some dogs a little grumpy, but a few may become stressed enough to bite. 

The Dog’s Size

Are small dogs more aggressive than large dogs? There is some evidence to support the theory. For example, one study published in Applied Animal Behaviour Science found that small dogs more frequently tried to bite. Their size makes them more defensive than large dogs. 

It may also be that people do not feel as threatened by a Chihuahua as by a Rottweiler. Therefore, aggressive behavior may be overlooked and allowed. Some people may even think it’s cute, that is until they’re bitten.

Psychological Factors

Unfortunately, some dogs live part of their lives in unhealthy, cruel conditions. They live in the homes of hoarders, are confined in small spaces, are taken from their mothers too soon, or are otherwise abused and neglected. These dogs are often aggressive out of fear and lack of socialization.

The Dog Parents’ Role

You may be surprised to learn that dog parents and other humans in the family may inadvertently encourage aggressive behavior in their dogs. 

Ignoring, Excusing, or Mismanaging the Behavior

Your friend’s dog is growling and barking at you. Your friend says, “Don’t worry. He won’t bite.” Your friend is giving the dog permission to act this way.

Your friend’s child is playing roughly with the dog. Finally, they have had enough and start growling, but the child won’t leave the dog alone. That is a bite waiting to happen.

Your friend’s dog is lunging and barking at someone. Your friend pets them and tells them to calm down. But the dog interprets that as encouragement. 

Your friend allows their dog to do whatever they want. The dog becomes aggressive when someone gets in their way.

Instinctive Behaviors: Drives

We divide a dog’s instinctual behavior into three categories or drives. Aggression can be triggered in any drive. 

  • Prey Drive: hunting, killing, and eating
  • Pack Drive: reproducing and living in groups
  • Defense Drive (Fight and Flight): reacting to what they perceive as threats

Prey Drive

A dog high in prey drive may act aggressively toward anything that moves, not just small animals. Cars, joggers, people on bikes or skateboards, dogs large or small can all give your dog reason to give chase. The dog may also aggressively guard their food bowl as though someone was trying to take it away. 

Pack Drive

Aggression problems may arise if your dog is not secure about their place in the family’s social structure. If you have not established yourself as the alpha, the pack leader, your dog may decide they need to take on that role. But that is not their natural place. So they will try to be the protector when you don’t need protection and may try to attack people perceived as threats.

If your dog turns their aggression on you, and you respond with fear and backing off, your dog will learn that aggression works and ranks them higher in the pack. 

Defense Drive

Your dog may exhibit aggressive behavior when they believe they need to defend themselves, their territory, belongings, or you. A dog in Defense-Fight drive may growl, bare their teeth, or lunge at other dogs or people because they perceive these others as a threat. In the worst cases, they will attack and bite. A dog in Defense-Flight drive wants to flee the situation. But if there’s no way to flee, they will fight out of necessity.

Next Month: Handling Your Dog’s Aggression (Part 2)

Once you find the root cause of your dog’s aggression, you can focus on effectively and safely ending it. Next month, we will post Part 2 of our discussion of dog aggression. We’ll talk about dealing with health issues, training techniques, and when you should seek the help of a professional trainer. 

Most aggressive dogs are just trying to protect themselves and their pack or are not socialized enough to know how to behave. But they can be trained and rehabilitated to become good dog citizens. Stay tuned for next month’s post!