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Why Is My Small Dog Aggressive Towards Big Dogs?

Adrienne is a certified dog trainer and former veterinarian assistant who partners with some of the best veterinarians worldwide.

Small dog attacking big dogs.

Small dog attacking big dogs.

Small Dog Aggressive to Large Dog

It's not unheard of: Rottweilers, Great Danes, and Saint Bernards are out for a stroll when pint-sized dogs gather, trying to attack these larger dogs who come in peace. What gives? How can these itsy-bitsy tiny dogs have the courage to attack dogs who are multiple times their size?

It's a question worth pondering as it goes against survival instinct. No human would chase a Tyrannosaurus Rex, and if he did, he better have some type of weapon that he could entirely rely in order to take down such a larger opponent!

Sadly, we all also know stories of small dogs with big attitudes who attacked a larger dog and, within seconds, the larger dog was able to subdue the little one, often with dramatic results. All it takes is one bite and a head shake to kill the little ones.

It's imperative that small dog owners always keep their little dog under control if they have a tendency to attack bigger dogs. This means giving up on retractable leashes, which put the small dog in a vulnerable position ahead, giving little control in case of an emergency.

So, why do small dogs try to attack bigger dogs? Because we can't put ourselves in a dog's mind or interview these small, feisty fellows, we can only make assumptions. In the next paragraphs, we will look at some possibilities.

It's not the size of the dog in the fight, it's the size of the fight in the dog.

— Mark Twain

5 Reasons Why Some Small Dogs Are Aggressive Towards Bigger Dogs

If you own a small dog who tries to attack larger dogs, you may be interested in learning why your pampered pooch may engage in this activity. The intent may vary from one dog and another, and as with many other doggy behaviors, there are really no rules set in stone.

These are just assumptions. Consider that many small dogs are often anxious and hyper vigilant, which puts them in a constant state of stress that lowers their immune system, making them more prone to disease. Here are some reasons why your small dog is aggressive towards larger dogs.

1. The Dog Thinks He's Bigger Than He Is

This hypothesis comes from veterinarian Marty Becker who claims,

"I sometimes wonder if little dogs think they are big dogs because they’re always looking down at other dogs from the relative safety of their owners’ arms or purses."

There may be some truth in this, as small dogs may gain "strength" and feel more potent when they are in their owner's arms.

2. The Way You Play With Your Dog Is Reinforcing Aggressive Behavior

Dogs tend to repeat behaviors that have a history of being rewarding or providing some sort of advantage. If your small dog once tried to put off a dramatically offensive display towards a bigger dog and the bigger dog retreated, the small dog will feel compelled to use the same strategy next time. As the small dog rehearses this, soon a behavior pattern establishes and eventually becomes the standard modus operandi.

3. Because It's Easier to Attack From Behind

In some cases, the other dog doesn't intentionally leave because he was intimidated by the small dog's display, he just leaves because he was just heading somewhere else. What happens here is that some small dogs take a cowardly approach by attacking other dogs from behind.

These dogs do nothing when the dog is in a frontal position; rather, they stealthily wait for the big dog to pass by. Once his hind quarters are in plain view, the small dog goes on attack mode. From the small dog's perspective, he has just "sent the big guy away." Mission accomplished. You can almost see them proudly patting their backs.

4. Breed Predisposition

This in particular applies to the small terriers. The term terrier derives from the Latin word "terra" which means "earth." This name was given to them because these dogs were often used to work in burrows to capture quarry. Terriers were selectively bred for "gameness."

This led to determined dogs who would persevere despite challenges. In the case of small working terriers, this meant being blessed with courage and initiative necessary for dealing with life/death situations in their encounters with vermin.

The low arousal threshold typical in these dogs allowed them to go from completely calm to full-blown fight mode quickly and with very little provocation, explains Dawn Antoniak-Mitchell in the book Terrier-Centric Dog Training: From Tenacious to Tremendous. She adds that,

"[terriers] have no real sense of their physical size and will tackle a larger animal in the blink of an eye, under the right circumstances."

Additionally, once a working terrier is aroused and ready to chase, fight or kill, it's very difficult to get him to listen to you.

Sounds familiar? Well, this same genetic wiring that made this breed so tenacious and courageous may not exclusively apply to vermin, but larger animals as well, including dogs, especially those who approach too fast.

Dawn-Antoniak- Mitchell indeed explains that this gameness fad was so very popular, that in the past terriers were expected to get aroused at the sight of other dogs in the showing ring and this was the ultimate "proof" of correct terrier temperament!

Other than terriers, Chihuahuas are also known for being "tiny in size but large in spirit." Indeed, many find their behavior to be similar to terriers: spirited, confident, feisty, and brave.

5. Unsolved Behavior Problems

When small dogs develop behavioral problems, these problems are often overlooked for the simple fact that there's belief that they're not capable of causing harm.

Small dog owners often fail to socialize their small dogs enough and they may be over protective, picking their dogs up the moment a big dog approaches. These under socialized dogs therefore turn out to be good candidates for fear aggression directed towards other dogs. It's important once again to seek help for any form of aggression/reactivity, whether displayed by a small dog, medium dog, or large dog.

As seen, whether it's genetics, poor socialization, or a case of "small dog syndrome," small dogs are vulnerable if they are not under control and have a tendency to want to pick up fights with the larger fellows. If you own a small dog, keep him safe. That means always leashed on walks (avoid retractable leashes) and at home in a well-fenced property he cannot escape.

Raising Awareness

If your small dog is attacked by a large dog, have him see the vet, even if you do not see visible injuries. It's like just seeing the tip of an iceberg. There are always chances for internal injuries such as brain and spinal cord injuries, and even severe damage to internal organs, according to Greenbrier Emergency Animal Hospital.

This article is accurate and true to the best of the author’s knowledge. It is not meant to substitute for diagnosis, prognosis, treatment, prescription, or formal and individualized advice from a veterinary medical professional. Animals exhibiting signs and symptoms of distress should be seen by a veterinarian immediately.

Questions & Answers

Question: How do I stop a small dog from acting aggressive and barking at big dogs?

Answer: The best way is through desensitization and counterconditioning.

Question: How do you train a small dog from acting aggressive and barking at big dogs?

Answer: One of the best ways is through desensitization and counterconditioning.

Question: Why does this article assume the fault is with the small dog? What about big dogs who can’t read the signs that the little dog doesn’t want to play? Or, owners with big dogs that can’t keep their dog under control. That’s why my small dog is now wary.

Answer: I am sure you own a small dog and have encountered rowdy large dogs who are not respectful of your dog's space. I hear you and you are right, so many small dogs become aggressive due to wrong encounters with larger dogs. Your case follows my generalization of "The intent may vary from one dog and another, and and as with many other doggy behaviors, there are really no rules set in stone." I am a big advocate for play groups divided in base of size, large dogs play with large dogs and small dogs play with small dogs, for the purpose of avoiding physical and emotional scars.

Question: My little dog used to love being around big dogs, but now he doesn't. He doesn't attack; he's just nervous. How do I get him to socialize with big dogs again?

Answer: Many dogs get more discriminative once the reach social maturity at 2-3 years of age. It's just part of them maturing and no longer feeling in the mood of playing with all the dogs they meet. If socialization is important to you, you can try to just restrict his contact with a few good friends that he plays well with rather than meeting a bunch of dogs who engage in rude behaviors at the dog park. Most likely, these dogs are those who also may have contributed to him being nervous in the first place. Pick dogs who share his play style and who your dog seems comfortable with. Have a behavior professional help monitor the first days to ensure a good match.


Adrienne Farricelli (author) on September 06, 2020:

Hi Edd, thank you so much for the update! You posted 6 years ago about your rat terrier exhibiting aggression toward larger dogs. I am glad that you were able to help her out through positive reinforcement and that she is able to be calmer on walks.

Ed Palumbo from Tualatin, OR on September 05, 2020:

Happy to report my rat terrier mix is much more improved and doing well. She no longer initiates contact or tenses for it. She's about 10 years old now and is very trusting and affectionate to my wife and I. She walks well on the leash. It took quite a while of "positive reinforcement" but she's a fine member of the family.

english bull terrier on August 14, 2020:

I have a lovely English Bull Terrier who is non-aggressive but extremely strong. I walk her several times a day through the neighborhood on a sturdy lead. Today as soon as we crossed the street and started our walk, a tiny leashed dog that looked like a rodent started yapping and would not shut up. Naturally my dog was pulling at her lead trying to find out why a rodent-like animal 200 feet away was making such a commotion. The woman picked up her dog and went into a yard but the constant, out of control, high pitched yapping continued. As I tried to proceed with our walk, the yapping continued and the woman was hiding behind a tree clutching her dog. I couldn't listen to the hysterical yapping and needed to control my dog on slippery pavement in the rain, so left and went home. I have had English Bull Terriers in the past that could grab a rodent (including a skunk) and snap their neck in a couple of seconds. I would like to walk my usually calm dog in peace and quiet without having to go home because of a yapping out of control 2 pound dog. My dog has only barked once in the last 5 months and doesn't growl. But I also know that she might not recognize a yapper like today as even being a canine - she might think it was a rat, if I fell and lost control of the lead. Even if my dog have paid no attention to it, I would still have had to leave because the continuous yapping was migraine-inducing. The worst part is that I couldn't even walk on another street because the yapping continued and could be heard for hundreds of feet.The dog's owner must be oblivious anyway since when we first saw them, she was letting her dog potty in the middle of the street.

Darlyn on May 15, 2020:

My six year old Shih Tzu (female) is always lunging and snapping at larger dogs and I have no idea why. Like, this friendly Labrador retriever (male) Came up to her and rolled a ball for her to play with and then she just lunged at him. I’m confused because she didn’t lunge at the other smaller dogs.


Daniel Wanke on February 10, 2020:

Why did humans breed canines into useless toys like the pomeranian?

Maggy on November 03, 2019:

I have a large(80lbs) puppy(13mos.), he just got attacked by a small dog(20lbs tops), the small dog was unleashed and he just went at my dog, we tried to run,I tried to pull him away from my pup, i tried blocking him from bitting my dogs legs, I had to start kicking, he just wouldn't stop, he wasn't listening to his person, just went bananas. My question is, what should I do to avoid this, this is not the first time I have had this issue, very small dogs attacking my dog, he has responded after repeated bitting, but, if he is not cornered he just runs away.

Misselenais on December 03, 2018:

My huskies are OK, not aggressive but do no respond well when provoked. Last night, a littler terrier dog was visiting, and the little terror would snap and snarl at my husky if he walked near by. He really did not like this behavior, and would grumble at me in response. He would not leave the little dog alone, and kept trying to go over and introduce himself. I tried to manage as best I could, but the little terrier was not getting any kind of support and the situation escalated. The little dog lunged at my husky, and of course my husky had it on its back in .0001 seconds, teeth around the little dogs head. He didn't bite or shake, he just pinned the little dog but I am worried now that the little dog will forever be afraid of my dog, and the owner will think my dog is aggressive. He isn't normally aggressive, he does not like being challenged in his own house. What can I do?

... on September 06, 2017:

We have a cairn terrier who will more than happily start fights with dogs four times his size. Despite this, he's great with people and would never harm a person, or a dog nearer or smaller to his size. They're confusing creatures...

Sweet Big Dog Mama on June 19, 2017:

I am so sorry MurphysMum. I just had a similar incident happen with a loose aggressive Chihuahua. My 2 big dogs do not go around looking for fights either. WE were charged and I yelled to stop the little dog and it did not listen at all. I don't think my dog even knew what was happening! So scary and my dogs were on leashes in a heal.

MurphysMum on November 04, 2016:

My retired neighbor walks my wolfhound cross three times a week for 2-3 hours on the days that I am at work. Last Wednesday when they were walking, a Chihuahua came suddenly running out of a front yard at my large dog. My dog is not that keen on meeting other dogs on the go, prefers the one-on-one meeting at home with me or other people he knows. So my neighbor and I always cross the road or get out of the way of dogs he doesn't know to avoid problems. My dog was on a leash walking with my neighbor on a public foothpath when the Chihuahua stupidly attacked my dog. Now the Chihuahua's owner is going around telling people my dog attacked his dog, he's put up a shrine outside his house for his dog that had to be euthanized (which is really sad but unprovoked by my dog, my neighbor or me). On top of that, the owner has come to my house twice. I listened to his story, was sympathetic when I first found out until he said he wished my dog was dead. I told him that if he were to speak like that he should leave. He carried on a bit more before he left only to come back the next day when I was at work. He entered my backyard and went into my master bedroom. He and his wife were irresponsible letting their dog run around without restraint, my privacy has been invaded, the couple are bad-mouthing my family and my dog will have to wear a muzzle, just in case other dog-owners conduct the same irresponsible behavior. My dog shared a house with 8 guinea pigs for 16 months. They are outside now in a big aviary kind of thing. We also have a chicken (Guardian of the guinea pigs) that my dog doesn't touch. I just wish people would take responsibility for the care of their animals. The fact that I typed in "small dogs attacking larger dogs" and an article mentioning specifically a Chihuahua comes up, makes my feelings of guilt and 'what could I have done to prevent this' a little easier. Two sleepless nights, not focusing at work, $65 on two muzzles, my caring loving dog now branded a criminal for being big, black and not keen on unknown yappy dogs, a visit to the police station to stop the owner from coming onto my property.... How I wish it was still Tuesday....

Joyfulcrown on January 24, 2015:

You can see from my profile that I have a small dog, a Maltese. He is always aggressive to one particular dog. He just doesn't like that one dog for some reason. Thanks for the article. It was helpful.

Tiana Dreymor from Columbus, OH on March 24, 2014:

It was, because I had been raised with big dogs and I never dreamed that would happen to my Honey.

Adrienne Farricelli (author) on March 23, 2014:

Sorry to hear that Vista15. That must have been devastating.

Tiana Dreymor from Columbus, OH on March 23, 2014:

I wish I had known... I had a Pom killed by a German Shepherd.

Adrienne Farricelli (author) on March 23, 2014:

Hello Faith, thanks for voting, pinning and tweeting. Your Jack Russell seems to match the profile of the typical working terrier depicted by Dawn Antoniak-Mitchell in her book " "Terrier-Centric Dog Training: From Tenacious to Tremendous"

Adrienne Farricelli (author) on March 23, 2014:

Thanks for stopping by Edward, you're very welcome. Generally, unfortunately this type of behavior tends to not get better with time as it's self-reinforcing , you may be interested in the Look at that Dog method:

Faith Reaper from southern USA on March 23, 2014:

We had a Jack Russell terrier who thought she was a big dog, I guess, and was fearless of the large dogs, and she would become aggressive towards them. Interesting and useful article.

Up and more, pinning and tweeting

Ed Palumbo from Tualatin, OR on March 23, 2014:

Despite its docile and affectionate behavior in the home, my rat terrier mix consistently exhibits aggression toward larger dogs. We adopted her a year ago from a refuge; she's happy in our home and has blended in well, playful and gentle with our dachshund and cat, but she's difficult when we walk and strains at the leash to engage other dogs (especially males). I hope that wears off with time and familiarity with environment, but I am concerned. Thank you for this article. I enjoyed it!