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Posted on Wed, Jun 12, 2013 : 8:45 a.m.

What are the most aggressive dog breeds? A university study provides interesting insight

By Lorrie Shaw


Lorrie Shaw | Contributor

I'm always amazed to hear the preconceived notions that people have of dogs in general.

The one topic really makes me shake my head: The misconceptions of dog aggression — particularly when it comes to breed. In working with any number of breeds on a given day, I can attest that aggression is far less common than one might think.

The truth is, any dog can become aggressive. But there a handful of breeds that rise to the top when it comes to exhibiting this most-unwanted behavior, and the findings of a study done by researchers at the University of Pennsylvania will certainly make one stop and think.

In my experience, I can say that the study, published in an issue of the journal Applied Animal Behavior Science, a few years ago, reflects what I see on a regular basis: the breeds of dog that have a higher incidence of aggression, snapping or attempting to bite strangers, their own humans and other dogs tend to be small breed.

In fact, the top three, are in order — dachshund, chihuahua and Jack Russell terrier.

So, is it a Napoleon complex? Something else?

A researcher who worked on the study, Dr. James Serpell, says that smaller breeds may have a genetic predisposition towards aggressive behavior than larger dogs.

"Reported levels of aggression in some cases are concerning, with rates of bites or bite attempts rising as high as 20 per cent toward strangers and 30 per cent toward unfamiliar dogs," he noted.

The study included questioning 6,000 dog owners. Breeds that scored lowest for aggression included Bassett hounds, golden retrievers, Labradors, Siberian huskies.

It's interesting to note that the Rottweiler, pit bull and Rhodesian ridgeback scored average — even below average for hostility towards strangers.

Greyhounds rated the most sedate.

One important note, citing the study:

Our results indicated that there are certain types of aggressive tendencies (territorial, predatory, and intra-specific aggression) that are not reliably exhibited during temperament testing using this particular evaluation process

One reason that these smaller breeds don't make for noteworthy attention when it comes to any hostile behavior is clear: because of their size, a chihuahua won't inflict the same amount of damage as a larger dog.

As an aside, I notice all too often that the signs that a small breed dog is conveying that they are uncomfortable with a social situation — sometimes because of their babyish size and appearance — can be overlooked.

Do owners of these breeds have a tendency to not have the same criteria in mind when it comes to teaching them self-discipline as they might for a large breed dog, like training classes?

There are many complex reasons, beyond genetics, surely.

In any case, it's vital that we understand that every dog has the capacity to behave aggressively. More importantly, it vital to note that in most cases, they choose not to do so, just like us.

Lorrie Shaw leads the pets section for Catch her daily dog walking and pet sitting adventures or email her directly and subscribe to's email newsletters.


Denise LaChance

Sun, Jun 30, 2013 : 4:36 p.m.

@buvda fray Unfortunately small dogs CAN cause disfiguring and fatal injuries


Thu, Jun 13, 2013 : 11:03 p.m.

Small dogs more aggressive? Nothing new here. The part about which dog will cause the most damage was sadly given short-shrift in this article however. Think about it, would you rather be bitten by a chihuahua or a pitbull? The terrier is going to punch you full of holes. You will be in great pain and might get an infection if you neglect it. However it won't be the life-altering event that you will experience if a Rott removes a portion of your anatomy; fingers, calf, nose. Also, how many times do you hear about a pack of taking someone down in the street and killing them? Just pointing out an important point of the argument which is often ignored.


Thu, Jun 13, 2013 : 2:35 a.m.

Good article, Lorrie. We had to shop for homeowners insurance when we closed on our house. Geico, and quite a few others would not insure us because they considered Bree (my Alaskan Malamute) to be a wolf hybrid. She, in fact, is the friendliest dog on the planet. She has never bitten anyone.

buvda fray

Thu, Jun 13, 2013 : 1:58 a.m.

People always want to talk about pits and mastiffs. Here we have proof that the little nippers are aggressive breeds. Now if they could just inflict permanent disfiguring injury, lunch on infants, turn on their owners, "Jekyll and Hyde" themselves from cuddly blockheaded mutts to relentless menaces seething with venom and kill people in their completely unpredictable fits of rage like pits and mastiffs, maybe they could grab some headlines too!

J. Sorensen

Wed, Jun 12, 2013 : 4:31 p.m.

In a previous decade I read meters for DTE. When entering a backyard for my read, a herd (as in 20+) Yorkie's rounded the corner all barking and nipping at my heels. No other dog confrontations ever frightened me like that!


Wed, Jun 12, 2013 : 3:20 p.m.

I enjoy watching those fearless little dogs run and try to dominate the big dogs at the dog park. My big dogs will run from a terrifying Terrier, that's fine with me. Out-of-control small dogs often have been coddled and babied so much that narcissism takes over. People forget that they need to train their small darlings just as we do larger dogs. Train them to wait their turn, to not bark excessively, and most of all find a way to curb their possessiveness. That said, I adore small dogs, they surprise you with larger than life personalities!


Wed, Jun 12, 2013 : 2:13 p.m.

When I observe dogs - and their owners - I'm sometimes amazed by the type of behavior little dogs get away with. If my large dog even looked like he was thinking of being that aggressive I would be in a lot of trouble. But not all little dogs are big trouble. Fozzie and I met a tiny Yorkie at the pet store. This pup was so sweet and friendly. She put her little paws on Fozzie's nose to get a closer look at him. And he let her because her body language indicated "friendly!".


Wed, Jun 12, 2013 : 1:56 p.m.

HA HA!!!! I love it. So us dog people have known this all alone. Small breeds are BY FAR the most aggressive.....little dogs have Napoleon complexes by default I think. I've met exactly ZERO small and toy breed dogs in my life that didn't have a bit of aggression. I'm not saying they were vicious, I can only remember one vicious small dog...but they ALL were energetic and initially aggressive when meeting them. They also all calmed down once they no longer perceive you as a threat....and for toy breeds a 6'4" human can be threatening. Still...I don't like this breed labeling. It's no different than saying something that would be considered EXTREMELY biased and "black people have a propensity for aggression." It is NO different.