Top 3 Reasons for Aggressive Dog Behavior, and What to Do About It


We’ve talked about aggressive canine behavior more than once on this blog (check out “He’s Not Mean, He’s Scared” and “Normal Dog Play vs. Aggression” for two recent posts). But I’m bringing the topic back up today for several reasons.

Recently I saw a friend at the grocery store, and the first thing she did was tell me about how her aging Chihuahua, who used to be so great with the family’s children, had started to get very impatient and snappish. Sometimes older dogs can do that, and it can be bewildering to owners who have always known their dogs to be sweet and friendly.

Another reason this topic has been on my mind lately is due to the large number of misplaced dogs after the flooding in Texas and the fires in California recently. Dogs that are scared and confused often exhibit signs of aggression, leading to fearful reactions form humans when what they really need is some gentle understanding.

With all of that on my mind, I decided to take another look at this topic with you. Dog aggression is anything that threatens to harm some other person or animal. So snarling, growling, barking, lunging, snapping, or biting, can all be considered aggressive behaviors. But it’s the why behind aggression that interests me. After doing a lot of reading on the topic, it seems to me that the best way to understand dog aggression is to break down all the many reasons into three basic categories.

Aggressive Dog’s Products On Amazon

Click Below To Go To AmazonRatingPrice
The Dog Aggression System Every Dog Owner Needs

Fear or Anxiety

Probably the most common base cause of aggression in dogs is fear, or anxiety. These two feelings instantly set off any creature’s fight or flight response, and for dogs, the fight response seems to be more pronounced. In some cases, fear is a response to a threat, and the dog feels that it is defending against something bad. In other cases, the anxiety may be a mental condition that can be treated with medication. Here are the differences between the two:

Fear is generally very specific. It has a visible target. As in, “the thunder is very loud and I’m afraid of it”. You’ll usually see this type of fear-based aggression in dogs that are afraid of men, children, bicycles, other dogs, and so on. They have a specific target for their fear.

Anxiety on the other hand is more generalized. Dogs are confused or don’t know what’s going on, and that makes them feel vaguely anxious. This is often found in dogs moving to new homes with new families – they just don’t know what’s going on yet.

These two things can be combined as well. A dog who is sick may be both fearful of the specific pain he’s feeling, and anxious because he’s not sure what’s going on with his body. This can lead to wanting to guard against or defend against what are perceived bad feelings, which can lead to random aggression.

Fear or anxiety may be caused by something physical going on inside your dog, such as a hormonal imbalance or a disease. They may also be caused by learned behaviors. For example, if a dog was previously taught to fight other dogs, they have learned to be anxious and fearful around dogs that look bigger or tougher than they are. Finally, fear and anxiety could be caused by the environment, such as with thunderstorms.


Frustration is one way to say that a dog’s needs aren’t being met. There is something that they need or want that they can’t access, and this is causing them to feel frustration. Because dogs don’t have words to tell us what’s wrong, aggression becomes one way of communicating the unfulfilled need.

For example, if a dog is recently being trained to a leash, and has never experienced walking on a leash before, they may feel as though they are not being given enough control over their movements and personal space. This can be very frustrating for a dog who doesn’t “get it” yet. So they may react with what is known as leash aggression, or becoming very aggressive and territorial towards other dogs or people who they pass while on a leash.

Frustration may be caused by something physical going on, such as being on a leash. It may be caused by learned behaviors. For example, if a dog has learned to respond to one set of commands and expectations, but a new owner is expecting other behaviors and commands, the dog may be confused and frustrated. Finally, frustration may be caused by the environment, such as a dog who doesn’t have their own safe space to claim, like a bed or a dog house.


While it’s not the most common reason for a dog to be aggressive, pain is probably the most commonly known reason. Any time a dog has a sudden and drastic change in behavior, the question of whether they may be in pain will be a priority. This is because it’s a primitive instinct for a dog to attempt to make itself appear scary when injured; it deters any would-be predators from taking advantage of the injury. However, there are many things that a dog may be experiencing that they register as pain. For example, it could be physical pain from poor dental health, arthritis, digestion issues, sore paws, and so on.

However, pain in dogs could also describe emotional pain. For example, a jealous dog who just met the new puppy is experiencing the pain of not having their owner’s full attention. Pain can be physical, as with being injured or will. Reacting to pain in an aggressive manner could be a learned behavior, especially if a dog was ever subjected to animal abuse. Finally, aggression due to pain can be caused by the environment, such as big changes that make a dog feel jealousy.

Things to Consider When Met with Aggression

These three basic categories can tell you why a dog may be feeling like they need to fight you. But as you saw in each category, even within those very basic categories, each could be caused by either physical, learned, or environmental factors. You can think of those factors as motivators. Some motivator is causing the feeling of pain, fear, or frustration. The first step to figuring out how to help a dog, is to figure out what is motivating them to the aggression.

So here’s what you need to ask yourself:

  • Could the dog be suffering from a disease or condition?
  • Could the dog be suffering from a medical condition such as a hormonal imbalance?
  • Could the dog be genetically more apt to cope with certain feelings through aggression?
  • Could the dog be displaying behaviors learned from negative experiences?
  • Could the dog be poorly socialized?
  • Has the dog’s environment recently changed?
  • Is the current environment full of stressful stimuli, such as lots of loud noise?
  • Has the dog had enough exercise lately?
  • Is the dog getting proper nutrition?
  • Could the dog be bored to tears?

Any of these motivators could be the reason behind either fear, pain, or frustration.

What Not to Do When Faced with Aggression

As the title of this article implies, we’re going to discuss some ways to help handle aggressive dog behavior. But first, here are some things that you should avoid when faced with an aggressive dog – both for your safety and theirs.

  • Don’t let the aggressive behavior continue. This could solidify the behavior as a good coping method for whatever is going on inside the dog’s head, which will make it harder for them to break the cycle in the future.
  • Don’t attempt to intimidate the dog in return. This is an old training myth that will only make things work.
  • Don’t ignore the signs that your dog is getting stressed. If you can get them away from a stressful situation before they become aggressive, it will be better for everyone.
  • Don’t ignore your dog’s exercise needs. No matter how busy you get, your dog must have exercise. A lack of ability to burn off energy can result in aggression.
  • Don’t avoid the vet if something could be wrong with your dog. Your dog’s poor health is one of the first things that will cause aggression. Stay on top of your dog’s health to avoid this.
  • Don’t assume that your dog is just an aggressive breed. Yes, there is some evidence that aggressive behavior can be genetic; but any dog can be trained or provided for in such a way that they will not be too aggressive.

What to Do When Faced with Aggression

So now let’s discuss what you can do to help a dog who is struggling with an aggressive response to fear, frustration, or pain. First, know that you’ll likely need lots of patience to get through to a dog who has become used to resorting to aggression as a coping mechanism.

There are three main areas that the owner can address to help a dog start to leave this coping mechanism behind:

  • Meeting Needs: First and foremost, you need to ensure that your dog’s needs are being met. Be sure that there are no medical reasons for the aggression that need to be addressed, and be sure that they are getting plenty of exercise. Their needs may also include a private space just for them where they can feel in control. Kennel training a dog, or giving them a dog bed, is a great way to help them feel in control.
  • Situation Management: The next thing that a good owner should do is manage the situation. If your dog is in a stressful environment, where it’s loud, or filled with new people or new dogs, they should be removed the moment they start to exhibit stressed behavior. Additionally, your dog should be very well trained to respond to certain commands to calm down while you navigate to a safer environment.
  • Behavior Modification: The last thing that an owner should do is focus on behavior modification. This should typically take place when you and your dog are alone, and when they aren’t currently acting aggressive. Teach your dog how to relax and develop better self control, so that when you are in the situations where they start to become anxious, you can remind them to behave.

Keeping Others Safe

What if your dog has gone beyond simply threatening, and has become a real danger to others? Unfortunately, until you are positive that your dog has their aggression coping mechanism under control, you will need to put others’ safety above the comfort of your dog. Muzzles will likely be necessary any time your dog must be around other dogs or people, until you can trust them again. Be sure to get a muzzle like the Company of Animals version linked, because it still allows the dog to pant and drink water – their only two methods of cooling off.

The Final Verdict

At the end of the day, aggression has several underlying causes, and the motivating factors for those causes can be even more complex. If you want to learn more about how to help a dog get past their fight or flight instinct, I recommend the book “The Dog Aggression System Every Dog Owner Needs” by Jackie Ferrier. This is a science-based system that includes a lot of the same information I shared here. The plan takes you much deeper into how to really train a dog to relax, develop self control, and follow reminder commands as you exist stressful situations. I found the book enlightening, and when combined with positive training methods like clicker training, I think this is a great system that all dog owners should be aware of.

Aggressive Dog’s Products On Amazon

Click Below To Go To AmazonRatingPrice
The Dog Aggression System Every Dog Owner Needs
As for my friend? I encouraged her to take the dog to the vet. Older dogs are often going through health changes that have them frightened, and that’s why they’ve begun acting aggressive. Hopefully they are able to find out what’s wrong and give the dog some relief.