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Why Are small dogs so Aggressive?

Why Are small dogs so Aggressive?It is often suggested that small dogs are more aggressive simply because they are small and feel the need to defend themselves more urgently than their bigger canine friends. This was thought to be true based only on anecdotal observation. As you will see below, this has been confirmed by science. But the small dog in the story I share below was a seven-pound dynamo who didn’t seem to be afraid of anything.


“I’ve seen a look in dogs’ eyes, a quickly vanishing look of amazed contempt, and I am convinced that basically dogs think humans are nuts.” – John Steinbeck


True Story About an Aggressive Small Dog

Back in the day (1980s), we lived in southern California. And we had about a half an acre fenced and cross-fenced. But there was no driveway gate.

At the time we had three dogs, big, medium size and small. My big dog was a Malamute-Husky mix. He was big, mellow and 100% loyal. He could go anywhere without a leash and never leave your side. Actually, he was also a pacifist. Never saw him angry at anyone or anything. And lastly, he never barked one time in his entire life.

The medium size dog was an Australian Shepard-Labrador mix. Just an all-around great dog. He did want to kill my favorite cat; his jaw would tense and you could see it in his eyes every time that cat came close (which he often did). But he was so smart. He knew I liked the cat and always controlled his desire to kill the kitty.

The little guy was a Cockapoo mix. Great little dog. Full of piss and vinegar. He was playful and fun to hang out with. I think he weighed about 7 pounds but acted like he was the 100-pound alpha of the group.

Here Comes the Meter Reader Man

The day in question was the day I finally got my hands on a driveway gate and installed it. Now, the dogs could be loose on the driveway at night. But I closed the gate for the first time and let them loose while I went to the house to get the “Beware of Dog” sign.

I wasn’t in the house more than 15 seconds when there was a big outburst of barking and yelling. I ran outside with the sign in my hand and was greeted by the following scene.

Dog Size Matters!

meter reader man

Read that meter!

The big dog was sitting there watching with interest. Always the pacifist! The medium size dog was barking. But, being the gentleman that he was, that’s as far as he would go. But sitting on the grass with his legs out in front of him was the man that came once a month to read the gas meter. He had tripped backing over the curb.

And at his feet was my Cockapoo. Brisling with anger and ripping back and forth at the bottom of the guy’s pants. No fear in full attack mode. Fortunately he didn’t bite the poor guy. Had he come to read the meter 15 seconds sooner or 15 seconds later on his once-a-month visit, this never would have happened because I would have been outside. Perfect timing!

Does this little anecdote answer the question why are small dogs so aggressive? I don’t think so. But it sure illustrates that small dogs can really be aggressive little devils.


“If you pick up a starving dog and make him prosperous he will not bite you. This is the principal difference between a dog and man.” – Mark Twain


Scientific Study – Small Dogs Are More Aggressive!

We now have a study that goes beyond anecdotal observation that confirms that small dogs are more aggressive than their bigger counterparts. And four reasons were identified:

  • Age – Dogs tend to become more aggressive after about the age of 10. As smaller dogs tend to live longer than big dogs, this can be a real issue.
  • Fearfulness – This is real. Small dogs can fall victim to many more predators than say a big husky. Even an animal as small as an owl is a threat to a 5-pound dog.
  • Breed – The simple fact is that according to studies, smaller breeds are more inclined to aggression than bigger breeds. Is this correlation or causation? Grounds for further research.
  • The owner – Unfortunately, the owners of small dogs are less likely to spend the time or the money to get little dogs trained. And as you might expect, this makes it more likely that small dogs will behave badly and are often more violent. The good news is that you, as the owner, have the ability to take control of the situation. The little devils are trainable. All you need is the will to make it so.

Most Aggressive Small Dogs

There are numerous websites online that have published a list of the most aggressive small dogs. After reading through many of these lists I find that they are not in agreement. In other words, these lists are totally subjective since we are mostly relying on anecdotal evidence. So, I list here a few breeds that seem to appear on almost everyone’s list which seems to add some credibility to the claim.

Pekingese – A small fearless dog that acts like a bigger alpha dog if not properly socialized. Known to nip or bite if annoyed which makes them less that ideal to be around small children.

Chihuahua – Small, high-strung and very aggressive. They apparently know how small they are and if feeling threatened will bite as their first response.

Most Aggressive Small Dogs

Lhasa Apso

Lhasa Apso – Not surprising that it made the list as they were originally bred to be guard dogs. But they happen to be very trainable dogs. Note: I once had a Lhasa. Unlike many Lhasa’s, this one was as sweet as can be!

Dachshunds – Any dog specifically bred to hunt badgers is by definition fearless and aggressive. These dogs are usually one person dogs and make great companions.

Jack Russell Terrier – Strong, physical, high-energy, stubborn dogs. They do have a reputation as biters but these dogs are very trainable. Note: I once had a neighbor with 3 Jack Russell’s. They were typical strong physical examples of the breed, but they were wonderful dogs who never bit anyone.

All of the above listed dogs are trainable. So, if you are living with a little jerk of a dog, the ball is in your court.

A Final Thought

Please remember. We are talking in generalities and percentages here. There are lots of small, sweet well-trained dogs around that are not violent or aggressive. And conversely, there are plenty of big dogs that are too scary to go near. But if your dog is a little holy terror, take control and get the little one some training and better socialization. It really works.

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