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Why Does My Dog Always Pick Fights with Larger Dogs?

We’ve all seen it, and some of us have even laughed at the 6 pound dog lunging and barking at the 80 pound dog coming toward them. However, for the owners of the little dog it’s embarrassing, annoying, and can even be dangerous if that 80 pound dog takes the bait, since we all know what the outcome would be.

While every dog is different, based on personality and environmental influences (experiences they have had, past training, etc.), there are a few “general theories” about why some dogs feel the need to play David and Goliath.


I have a twenty pound Shetland sheepdog that I got when he was eight weeks old. At the time, I worked at a doggy daycare and thought it was the ideal place to bring a puppy. I already had two other shelties, both who were unsocial with other dogs and I was sure that being at a daycare would make our newest family member the friendliest dog ever.

If your little dog looks like this when he sees a bigger dog, fear may be the cause.
If your little dog looks like this when he sees a bigger dog, fear may be the cause.

Merlin, however, was not a quite or mild mannered pup by any measure. By the time he was 4 months, he was zipping around the little dog room and playing pretty rough. So the management decided he should be in the big dog room. While there were other smaller dogs in there, it was mostly large dogs, over 50 pounds. As he grew, Merlin started to get reactive on leash whenever he saw a big dog. And it just kept getting worse, even with the training we were doing. Since I was not in the big dog room a lot, it was several months before I started getting reports back that Merlin was having diarrhea all the time, he would sit by a door and howl, and “slink” around. In other words, Merlin was stressed.

Like many little dogs, he understandably saw big dogs as a threat and animals have two ways of dealing with a threat: flight or fight. For many dogs, their instinct tells them to fight. In their mind, they are thinking, “if I look tough and scary, that big dog may not come up to me.” This is something a lot of dog owners do not recognize:

A dog that is growling, barking, lunging at the end of the leash may actually be afraid of what they are facing.

The best thing to do in this case is avoid big dogs until you can work with a trainer. Trying to force your dog to be around them will make it worse.


“From the dog’s view there are two ways to increase distance: The dog can move (running away) or he can try to making the other dog move (by barking),” explains Robin Bennett, CPDT-KA, author of All About Dog Daycare.

If your dog is barking out of fear, then they are looking for that other dog to go away. And in most cases, the bigger dog does leave (maybe they aren’t interested, or their owner pulls them away). What does this mean?

It means your dog just got reinforced for barking to get something to go away (this same principle works for the mailman, the birds outside, etc). Which means the next time, your dog is even more likely to put on a big show when a larger dog approaches.

As Bennett puts it, “Practice makes perfect as they say…so the next time a small dog sees a big dog he will try the same tactic. With repetition this behavior can become really strong.”


There is also something to be said (warned, perhaps?) about the way we treat little dogs. They have become “purse dogs,” “accessories,” whose paws barely touch the ground the majority of the time. AND, when something is coming, our “parental instinct” kicks in and our first thought is to scoop the small dog up like a baby, to protect it.

“I also think small dogs sometimes do alert barking at big dogs as a way of asking their owners for help,” says Bennett.  “So the sequence is ‘bark bark bark’, then owner picks up small dog.  That can also be a cycle that, when repeated, gets stronger.”

Nicole Peterson, a dog trainer with a degree in Psychology, has seen something similar with her clients. “small dogs are often less socialized and allowed to get away with more unfavorable behaviors than large dogs. Because owners often carry them and do not treat them consistently like large dogs (who always have all four paws on the floor) they can become hyperactive and over-stimulated by [their environment]. Since a small dog is easily controlled, the behaviors like barking and lunging are never corrected and allowed to accelerate.”

And, in some cases, the owners may actually have contributed to their dog’s feeling of “helplessness” or need for “help.”

“Many owners treat them as more helpless than larger dogs,” Peterson says. “This means if a large dog comes up to sniff them, they may be quickly snatched up into the worried owners’ arms. The dog easily feeds off this anxious energy from the owner and exhibits it themselves over time.”

Remember, your dog can sense your emotions. So if you are anxious, stressed, and fearful, your dog will be too. If each time a big dog approaches your little dog, you tense up, shorten the leash, and then grab your dog up, he is going to think there is something he needs to worry about, even if he didn’t before.

This is especially important when you have a puppy, who is just learning about life and her environment. Do this enough times, and you will end up with a reactive adult.

If Your Dog Does This

These are theories! Do not go out and try to fix your dog just from reading this article. Every dog is an individual and their reasons for reacting to larger dogs will be just as unique as they are. The best way to rehabilitate your dog is to have a certified dog trainer assess both you and your dog and develop a training plan that fits your situation.

About the Author

Based in Wilsonville, Ore., animal lover Kristina N. Lotz is a Certified Professional Dog Trainer – Knowledge Assessed (CPDT-KA) and works as a full time trainer. She is the founder of, A Fairytail House, a unique all-positive all-sport dog training facility that helps rescue dogs in her area and provides free seminars and training classes for the community. In her spare time, she trains and competes in herding, agility, obedience, rally, and conformation with her Shetland Sheepdogs. She smartly married a Veterinary Technician, who helps keep the fur kids happy and healthy, and provides a quick resource for articles.

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Written by Kristina Lotz
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