What Causes Aggressive Dog Behavior?

Understanding why a dog displays aggression is the first step to effectively reducing and preventing it.


In a world where our canine companions are often referred to as our “best friends,” it’s a puzzle that so many dog-human communications (or should I say miscommunications?) result in behavior that we perceive as aggression – anything from a freeze (stillness), hard stare, growl, snarl, snap, or bite, all the way to a full-on attack.

If you asked your dog, he would likely say that these behaviors are just varying degrees of canine communication. He might also say, “My human made me do it.”

All these behaviors are natural, normal social expressions – the dog’s attempt to communicate something important. Usually, the mildest of the behaviors that people might recognize as aggressive – say, a soft growl – is not the first sign of a dog’s aggression. A growl is actually well along a continuum of escalating emphasis in canine communication. A dog who is uncomfortable will generally start trying to communicate his discomfort with much more subtle behaviors, such as avoidance, yawns, evasion of eye contact, lowered body posture, pulling ears back, and rolling on his back.

These behaviors are an attempt to resolve a situation without having to resort to serious aggression. Perhaps it’s a claim to a valuable resource: “I don’t want to share my bone!” Maybe it’s an expression of fear: “You’re making me very uncomfortable, please go away!” Maybe the dog is in pain: “That hurts, please stop!”

If the lower-key communications fail to accomplish their purpose, the dog may feel forced to escalate to more forceful or violent action (such as attacking and/or fighting) to get his point across.

Some or all of the mild, avoidant behaviors ordinarily precede the dramatic behaviors that most humans would recognize as aggression – yet most or all of these behaviors typically go completely unnoticed by many humans.

Alternatively, if these signals are ignored or misinterpreted, the human may respond inappropriately (“Oh, you want a tummy rub?”), forcing the dog to increase the intensity of his behavior and eventually escalate to serious aggression. Growling, snarling, snapping, or biting may seem like the “first signs of aggression” to many humans, but most other dogs (or experienced observers of dog behavior) would have recognized many earlier signs.

Why Are Dogs Aggressive?

When dogs display aggressive behaviors, it’s rare for humans to consider whatever the dog was trying to communicate. Instead, the behaviors are just considered unacceptable, threatening, and dangerous. Look at it from their point of view, though. Dogs are expected to just deal with all the situations they are put in (including many that annoy, terrify, or intimidate them) and to just get along with every dog or person they meet (including many that annoy, terrify, or intimidate them), without ever expressing their annoyance, fear, apprehension, or discomfort using their natural, normal canine communication tools.

We give them valuable resources – delicious food, delightful chew objects, comfortable furniture – and tell them not to covet those resources or protect them from someone who may try to take them away. If a dog does attempt to keep something for himself (with a growl or a snarl), he’s often punished. Dogs who try to communicate with normal canine language that they need more space, are annoyed or scared, or would like to keep something for themselves, are often labeled “aggressive.”

Consider this idea for a moment: Dogs are often forced to escalate – from mild growls, a stiff posture, and hard eyes to a lunge and a snap or worse – because we just don’t listen!

Granted, we can’t know for sure exactly what the dog is saying. As the supposedly more intelligent species, though, and with a better understanding of dogs, we can usually extrapolate something pretty close to the dog’s intent. And if we have an idea about what he’s trying to say, we can respond appropriately and take steps that will reduce the intensity of his communication, rather than forcing him to escalate.

The better we humans are at listening to and understanding “Doglish” the more our dogs will be able to communicate in ways that are less threatening to us while still succeeding in getting their needs and wants addressed.

snarling dog
Don’t punish this snarl and “hard look” – these are important early warning signs of the dog’s extreme discomfort. Dogs who have been punished for behaviors like this are apt to bite without warning the next time. Instead, de-escalate. Put some distance between you, decamp for a less stressful space, and start trying to figure out what triggered his distress. © Juan Jose Tugores, Dreamstime.com

Types of Aggressive Dogs

There is no universally agreed-upon scientific list of aggression labels. Various sources offer various names for different types of aggression, and those labels are constantly changing. There are, however, many commonalities. Below are descriptions of some of the most frequently seen presentations of aggression and the dog’s usual motivation for displaying each type.

For the purposes of this general discussion about aggression, I won’t be discussing specific solutions for each situation in which a dog might display aggressive behavior, but rather, the broad strokes of the most effective approach.

If you are challenged by your dog’s aggressive behavior, I strongly urge you to seek the assistance of a qualified force-free behavior professional who can help you create and implement an appropriate behavior management and modification program.

Fear-Related Aggression

This is by far the most commonly seen type of aggression, and one that humans often responds to most inappropriately. Generally, when a dog shows signs of fear and aggression, she is trying to compel those near her to move away; she needs more space to feel safe.

Many humans assume that a dog who is fearful will choose avoidance rather than aggression – and in many cases, that’s a correct assumption. If, however, a fearful dog is trapped, or has been trapped in the past, she may take a “the best defense is a good offense” approach, especially if there is a history of punishment for her agonistic signals. Keep in mind that “trapped” can include being on leash, being followed and cornered when she tries to retreat, or simply feeling confined in a small enough space that she is uncomfortable (such as your living room).

To make matters worse, it’s natural for humans to try to comfort someone who appears afraid – but this is often exactly what the fearful dog does not want, especially from a stranger or from someone who may have punished the dog in the past.

The first thing to do with a dog who seems to be aggressing out of fear is to give the dog a little more room – to put more space between the dog and the suspected fear-inducing stimuli. Then, start putting a counter-conditioning and desensitization plan into place, with the goal of changing how the dog feels about the stimuli.

Pain-Related Aggression

Every animal control officer knows that when you go to pick up an injured dog that has been hit by a car, you muzzle her first, because pain can easily cause even the nicest dog to bite. Dogs who are in pain generally don’t want to be touched and may show signs of aggression in an effort to get people or other animals to leave them alone.

What many owners don’t realize is that even less obvious pain can be significant contributors to a dog’s propensity to bite. Arthritis, spinal problems, sore muscles, gastrointestinal issues – there are numerous “invisible” conditions that can cause or contribute to a dog’s aggressive behavior.

An aging dog with increasing arthritis pain may begin to growl at approaching children because she knows from past experience that they may fall on or try to play roughly with her. “You’re making me very uncomfortable,” she says. “Please don’t come any closer.” A protective parent, outraged that the family dog would growl at the child, physically punishes the dog, adding to her pain as well as her anticipation of punishment when children approach, thus increasing the likelihood of her becoming more aggressive toward children, not less.

A far better solution: Any time you suspect your dog may be experiencing pain – or for any senior dog, or any dog who hasn’t been seen by a veterinarian for a while – arrange a veterinary examination and consultation as soon as possible. Ideally, your veterinarian can diagnose a condition and prescribe medication to alleviate the dog’s pain. Also, if necessary, use some basic management tools (such as baby gates, crates, or locked doors) to protect her from the unwanted, sometimes inappropriate, attentions of children.

Play Aggression

There is a significant difference between aggressive play and play aggression. Aggressive play is normal and acceptable, as long as both dogs are happily participating. This can include growling, biting, wrestling, chasing, body slamming, and more.

When things go wrong, it turns into play aggression. This can happen when one participant becomes uncomfortable with the escalating level of arousal and tries to signal that she wants to tone things down. If the other dog fails to respond to her signals and continues to escalate, she may aggress in self-defense, in an effort to stop the action. While she is often blamed for starting the fight, it is, in fact, the other dog’s fault for failing to respond appropriately to her request to back off the level of arousal.

The first step toward a solution here is to make sure you are pairing compatible playmates, and monitoring the play, giving both dogs a cheerful time-out when arousal levels are escalating to an unhealthy level.

Possession Aggression

My clients are often surprised, but soon nod in agreement, when I tell them that possession aggression, also called resource guarding, is a natural, normal behavior. If you lock your house when you leave, you are resource guarding! It is also an important survival strategy. In the wild, if you don’t protect your valuable resources, you die.

There is a tragically flawed and arrogant belief among some humans that they have the right to take anything away from their dog any time they please. Some misguided trainers even encourage clients to practice taking their dogs’ food bowls away so the dog learns to accept it. Wrong, wrong, wrong! Our dogs should trust that we won’t challenge them for valuable items, and we need to teach our dogs a voluntary “Trade” behavior, so we can safely ask them to voluntarily relinquish something when we need them to do so.

Take time to convince your dog that more good things happen when humans are near their food bowl and other good stuff, rather than teaching her that you are an unpredictable threat.

Predatory Aggression

Although the result can be devastating for the victim of predatory behavior, this is not true aggression – it is simply grocery shopping. Food acquisition behavior involves a different part of the brain and different emotions from true aggression.

It can be a challenging behavior to modify, but it is possible, depending on the intensity of the behavior, and the ability of the owner to manage the dog’s environment to prevent reinforcement for the behavior. The person also must make a commitment to doing the behavior modification work.

Redirected Aggression

This behavior occurs when a dog is highly aroused, but thwarted from addressing the object of her arousal.

Fence-fighting is a classic example. Unable to reach the dog on the other side of the fence, the dog may redirect aggressively in frustration to her own canine companion on her side of the fence, or to her own human, who is attempting to intervene in the barrier conflict. To avoid setting up the conflict situation, management is important. If intervention is needed, do it from a distance, to avoid being the target of a redirection.

Social Aggression

This is today’s term for what used to be called, unfortunately and inappropriately, “dominance aggression,” as a result of a serious misinterpretation of canine behavior. This label applies to situations where there is conflict between the wishes of the dog and her human(s), often where the human attempts to physically manipulate or control the dog (the phrase “manhandling” comes to mind!). A classic example is the dog who growls or snaps when the human tries to pull her off the sofa or bed, or push her into a crate.

As the supposedly more intelligent species, we should be able to get our dogs to want to do what we want them to do, rather than physically force them. Need your dog to get off the sofa? Toss a treat on the floor. Teach her an “off” cue. Teach her to go to her mat on cue. Teach her to target to your hand, or to an “X” on the wall made of blue painter’s tape. There are lots of ways to invite your dog to move where you need her to without using physical force.

Other Types of Aggression in Dogs

This is by no means a complete list of the various aggression labels. Others in common use include protection aggression, maternal aggression, territorial aggression, barrier aggression, and idiopathic aggression. What you call the behavior is, in many ways, less important than how you interpret and deal with it.

If your dog displays aggressive behavior, get help from a qualified force-free behavior professional who can help you create and implement an appropriate behavior management and modification program. Modifying aggressive behavior can be challenging. Your behavior professional will educate, encourage, and coach you, and support you when you’re feeling discouraged.

As stated by a meme that has been making the rounds recently, “Remember, your dog isn’t giving you a hard time – he’s having a hard time.” Stay strong, stay positive, understand and empathize with your dog’s hard times, commit to a behavior modification program, and you will be best able to help her overcome her challenges.

What Are the Most Aggressive Dog Breeds?

Go ahead: Google “aggressive dog breeds” and see what you get. The lists will be all over the place, from wolf hybrids, to the Tosa Inu, to Bull Terriers and German Shepherds, Rottweilers, Rhodesian Ridgebacks, Boerboels… I could go on and on.

Most of these lists make the mistake of confusing size and strength with aggression. Still, the Schipperke (at just 12 inches and about 15 pounds) is listed on one insurance company blacklist, and I found the Basenji (16 inches and about 24 pounds) on another list. While large, powerful dogs are capable of inflicting greater injuries on a human, there is absolutely no rhyme or reason to the listing of any breed as inherently “aggressive.”

For sure, there may be some breeds that are more heavily represented in dog bite, mauling, and fatality statistics. There are a number of reasons for this. Some breeds get listed as “dangerous” a result of just one highly publicized event. After a woman was killed by two Presa Canarios in San Francisco in 2001, the previously little-known breed immediately began appearing on “aggressive dog” lists.

Some breeds are just big and scary-looking. Other breeds are present in greater numbers in the pet-owning population, and thus are more likely to be represented in general bite statistics. Then there is the whole question of breed-identification; these days anything with a big head is likely to be identified in bite statistics as a pit bull-mix, even if it’s a Boxer mix or some other big-headed breed. And even if it’s a Lab/pit-mix, it will still likely be listed as a pit-mix rather than a Lab-mix.

Finally, certain breeds and types of dogs may be more appealing to – and more likely to be adopted or purchased by – people who are drawn to the idea of having an aggressive dog and who therefore elicit and reinforce aggression.

Of course, if a Rottweiler bites you, there’s a good chance you’ll be injured worse than if a Pomeranian bites you, and the big dog will be perceived as more aggressive because he has the potential to inflict more damage. But aggression is about behavior, not size, potential, or breed.

Keep in mind that behavior is always a combination of genetics and environment. A dog representing a breed that has been bred for guarding, placed in an environment that reinforces aggressive behavior, will indeed, become very aggressive. But, placed in an environment that reinforces sociability, he may end up well-socialized and friendly. And a dog who has been deliberately bred for sociability can be placed in an environment that reinforces aggressive behavior and end up very aggressive.

The bottom line is: breeds are not aggressive or friendly, individual dogs are.

Pat Miller, CBCC-KA, CPDT‑KA, is WDJ’s Training Editor and author of Beware of the Dog: Positive Solutions for Aggressive Behavior in Dogs.

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Pat Miller, CBCC-KA, CPDT-KA, grew up in a family that was blessed with lots of animal companions: dogs, cats, horses, rabbits, goats, and more, and has maintained that model ever since. She spent the first 20 years of her professional life working at the Marin Humane Society in Marin County, California, for most of that time as a humane officer and director of operations. She continually studied the art and science of dog training and behavior during that time, and in 1996, left MHS to start her own training and behavior business, Peaceable Paws. Pat has earned a number of titles from various training organizations, including Certified Behavior Consultant Canine-Knowledge Assessed (CBCC-KA) and Certified Professional Dog Trainer - Knowledge Assessed (CPDT-KA). She also founded Peaceable Paws Academies for teaching and credentialing dog training and behavior professionals, who can earn "Pat Miller Certified Trainer" certifications. She and her husband Paul and an ever-changing number of dogs, horses, and other animal companions live on their 80-acre farm in Fairplay, Maryland.


  1. I really enjoy reading about an authors view and experiences with animals It makes me feel good about people and their relationships with animals And their devotion to whats right and whats wonderful in life and rewarding as a full responsibility ……..I will confess in whole form It took me many years to establish a mature grounded appreciation for what most people may at times take for granted..Intimacy with a trusted Life or lives…Dogs and cats. If you made time close to an hour to sit down and calm down and look at your animal’s face their eyes An entire world of peace Understanding and regimented good and plain Active life awaits you …That is what a dog is ;;;;;;;;;A guide to discipline in its highest level. THe natural enjoyment of staying strong and bouyant and moving gracefully through all obstacles;;Poetry in motion is the domestic dog ………………….and cat!!

  2. I have a rescue Shih Tzu who was out on the street for some time and shows aggression on the leash to other dogs and most men. We have made some progress over the last 7 months that I have had her. I usually tell her calmly as we approach, if I can’t avoid, that it’s OK. This seems to be working for people, but not dogs. There is one male Shih Tzu that she likes and he is always off leash. Not sure if that makes a difference. She is fine in communal situations, so it’s definitely a leash issue. Any suggestions?

  3. I have a German Shepherd (Kody) that I love dearly, but find myself in a position where I need to give him to a friend because of his protective and possessiveness of me. It took me two (2) years before Kody’s eyes cleared of the abuse he had endured for the first year of his life; whereas I could no longer see the mis-trust, fear, confusion and wariness, not to mention the initial two (2) months of his refusal to even be in the same room with myself or any other human being! Unfortunately, almost immediately after his eyes cleared, a look of what I would call, obsession, could be seen when he would gaze at me. After a couple of months, he started placing himself between anyone else that was here, and myself, inside or outside. There were several signs of a coming disaster…I went so far as to having him stay a day or so with friends…he would not eat or drink while at these “sleep overs” and appeared extremely depressed and would whine constantly, according to my very knowledgeable, dog owner friends. I have to hold a squirt bottle of water to get my hugs from friends when they arrive or leave, and usually have to use it. I immediately started looking for another (or 2) dog(s) in an effort to enlarge our pack and distract his full attention from me. From Jan. of 2019 until last month, when I gave up, this proved futile as I could not find a dog which was acceptable to Kody (except for 1 that ended up attacking him after 2 months of suspicion from Kody finally stopped….Prince attacked Kody the morning after the first time Kody let him in bed with us). Took Kody’s acceptance (finally!) as a sign of weakness, I would suppose. It has just been he & I for three (3) years now, with a handful of friends in and out, except for my “house helper” that is here three (3) mornings a week. Kody adores all, ESPECIALLY my Eve!. It is my fault that Kody doesn’t get the Social Life that he needs & should have, to be balanced, whether he knows it or not. I have injuries from an auto accident that preclude much physical activity on my part (I have outdoor equipment that allows play when weather permits and I take him everywhere with me, tho I rarely leave the house). Eve, my “house helper” and beloved friend, also takes him for walks but he still growled at her last month when she was trying to help me get out of bed and then he tried (I was holding him and felt him stiffen) to attack her last Friday when she was trying to help me lay down on the sofa (luckily, I had tightened my grip when I felt him stiffen & she moved FAST). She said she would not be back, after having warned me the first time he growled last month, unless I did something about him. It is breaking my heart, but he is going to a new home tomorrow morning. Kody will be with a wonderful man who has two (2) other dogs, a 17 year old, 19 year old and a 22 year old son living with him. Kody will be going to work with him every day (he is the Director of a local Humane Society) unless Kody is going somewhere with one of the boys. They will be patient with him until he gets his bearings and he will finally have the home he deserves….not stuck all alone with an old, disabled broad. Am I doing the best I can do for this beautiful soul? He has been the light of my life for the last few years and I want him to be as happy as he has made me…Kody and I met with three (3) different “trainers” and all three (3) said “I was the problem” and they could not suggest any course of action other than finding him another home. I cannot stand the thought of this escalating further to a situation where Kody would have to be put down, because I allowed him to become too attached/possessive/protective of me. How could I have stopped this before it reached this point? I saw it coming almost a year ago by the look in his eyes (that is where I “see” a dog, along with stiffness of legs/back/neck). I never want to go through this again. It’s too late now in Kody’s case, as Eve will formally quit on Monday if Kody is still here, and I truly need her help as my physical condition has worsened considerably with this constant rain we are having here in N.W. Ohio. I can’t control that and my pain medication cannot control the pain, which pretty much immobilizes me for days at a time. I would greatly appreciate your advice; as I will get another dog…I cannot image living without at least one in my life. That would pretty much take away any reason to get up in the morning at all, for me. Thanking you in advance for any help you can offer.

    • Hi Brooke, I read your article and am wondering how Kody is doing? I worked with a non-profit until January that worked in the local city animal shelter and saw many a dog that would ‘resource hoard’ as Kody did. Many come back to the shelter as an owner surrender or are picked up running the street and were simply turned out. If your friend has had success with Kody then please sing praises everywhere you can. People who know how to train and coach both dogs and people about resource hoarding are THE ONLY CHANCE OF SUCCESS these dogs will have at a healthy life.

  4. My 1yr 1/2 doberman has this thing where he sneaks an object off the counter, table ect. such as towel, napkin, sock ect. When we approach him to get it, he releases it & he lowers his head. If I reach to get it he shows teeth and has bitten my hand. It seems like he lures me so he can attack. I need to fix this behavior because he wanted a yarn ball I had on my lap and when I went to cover it with my hand, he bit me. Can this behavior be fixed? My husband wants him gone.

    • You could try tossing a treat away from the item you want to get back, so that the dog has to abandon that item in order to retrieve the treat.
      I’d also teach the “Leave It” cue. Search on this site for instructions.

  5. why would my dog be aggressive towards older person living in home when that person is putting their dishes into the dishwasher. The dog ignores her most any other time. Said person ignores the dog, will not pet or acknowledge her in anyway.

  6. My dog, a fairly submissive beagle hound mix was recently at a dog park. She is a rescue. We have been going to this park for about a year. I also have a chihuahua Jack Russell mix. The smaller dog is mouthy. He growls and nips when most other dogs approach. Often I end up carrying him because he is fearful and shows aggression when he is bothered. That was the case today. My other dog loves to play and greet dogs as they come in. Today, another hound mix entered and my beagle hound greeted and proceeded to sniff the dog. The owners said they were trying to socialize it. Well their dog wasn’t comfortable and began to back away. My dog wanted to play, she did her play bow and tried to get the attention of the other dog. The other dog growled then began barking. Mine did as well and before you know it, a fight ensued. I grabbed my dog and we went and sat in the bench. The other couple was very upset and laid all the blame on my dog. Their dog ended up with a cut on its head. They would take zero responsibility for anything that happened. They also said another dog owner moved to a new area because of mine. I tried to explain that the other dog owner moved because her dog wouldn’t leave my chihuahua alone and I had to carry him. They wanted my name, license information etc., it upsets me because my dog has been submissive since day one of Adoption. I began to take her to the dog park to socialize her. She did fabulous. Sometimes bigger dogs would get aggressive with her and I was able to move her from the situation. NO ONE who encounters her would believe she was the aggressor, excited and playful yes. I take responsibility for my dog. When another doesn’t want to play, she moves on. She does react to another dogs growling and barking at her. I am now afraid that I will be encountering some unfounded vet bills. Who is to blame here?

    • Your dog does not like pugs! I had a cocker spaniel that was absolutely sweet to every dog in the world except golden retrievers. When he was about 6 months old I took him on a leash to my neighbors house to deliver mail. We had been there before but this time her sons golden was there. The goldie charged out the door, probably a guarding behavior, and it scared by puppy half to death. But – he got his footing right away and charged back at the Goldie. We lost our ‘Bingo boy’ at age 11 from kidney disease but he NEVER was anything but in perfect fighting spirit towards Goldies his whole life. I would suggest that you try some of the tricks and skills in WDJ, I did not.