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Reactivity: "Leash Aggression"

By far, the most common behavior problems in pet dogs is reactivity. Your normally calm, enjoyable dog that turns into a quivering, snarling, white-hot ball of canine terror at the mere sight of another dog on a walk.

It's frustrating and even embarrassing, and sometimes dangerous. It certainly is not what you imagined life would be like with your dog. It can even be incredibly isolating, as your dog can't participate in activities you once enjoyed, like hiking and camping with friends, or hanging out at an outdoor cafe. But you're not alone.

Reactive behavior does not discriminate by breed or background. It occurs in dogs purebred and mixed who were acquired as puppies from breeders and adopted from rescues. And it happens to dogs who live in responsible, loving homes.

There can be several causes for reactive behavior. These include:

  • Genetics

  • Early socialization deficits

  • Learning history/trauma

  • Pain

Yes, your dog's behavior could have a genetic component. Your dog's parents, either one or both, could have been reactive.

Dogs that did not receive sufficient socialization by 14 weeks of age, then throughout adolescence (5-18 months), and finally through adulthood are more likely to develop behavior problems.

Dogs that experienced a traumatic incident, such as being attacked by an off-leash dog, or even something that seems less traumatic, such as being bullied at the dog park too many times, can develop a negative association to other dogs.

Finally, a dog that is suffering from dysplasia, arthritis, or other conditions that cause pain, is going to be much more defensive about other dogs. While you might be trying to determine which of these is the cause of your dog's reactivity, it can be difficult to pinpoint and is usually a combination of more than one factor. It is not, however, simply due to a lack of love, leadership, or obedience.

In spite of all the lunging, snarling, growling and barking, some of these dogs are actually quite friendly to other dogs when off-leash. yet, when they are on-leash and on a walk, they become the canine equivalent of Mr. Hyde. This is why the behavior is more accurately referred to as reactivity; the dog is reacting to something in the environment. Simply being attached to a leash does not not incite aggressive behavior.


There can be many causes for leash-reactive behaviors including lack of early socialization, a traumatic experience, or simply a lack of training.

Frustration is what happens when a normally dog-friendly dog spots another dog, attempts to rush over to greet the dog, and hits the end of the leash.

Some high-energy dogs develop leash-frustration, especially dogs that regularly visit the dog park. These dogs learn that other dogs equal rowdy, unchecked play sessions and have poor self-control. When they spot another dog, they prepare to launch into their normal rowdy behavior, only to find themselves restrained by the leash. Their excitement quickly turns into frustration, which can manifest as reactive behavior.

Reactivity is when a dog that is conflicted about or fearful of other dogs encounters a dog on a walk. Being trapped by the leash, the reactive dog is forced to walk closer and closer toward the other dog, when he might otherwise have chosen to keep his distance. The barking, lunging and snarling are all signals to the other dog to go away.

From the dog's perspective, his reactive behavior is very effective. Because each time he barks, the other dog goes away. Because of this, the barking is reinforced every single time.


Despite the claims of a popular television show, lack of exercise is NOT a cause of reactivity. In the vast majority of leash-reactive cases, the dogs are exercised regularly.

In one recent case, the dog was being walked FOUR times per day for over 45 minutes to an hour each walk. Another dog was provided with a daily game of fetch until he had almost run to the point of exhaustion in an effort to tire him out for the rest of the day.

While physical exercise is just as important for dogs as it is in humans, it cannot solve behavior either species.


It seems to make sense to most people to expose the reactive dog to other dogs and then try to train the dog not to bark. However, once a dog is reacting to another dog, the part of the brain that processes the fight/flight reflex is active. When this part of the brain is active, the part of the brain that processes learning is shut off, so that the body can reserve as much energy as needed for survival. If you are being chased by a bear, you don't want your brain worrying about taxes. Dog trainers refer to this as the dog being "over-threshold", or past the point the dog can tolerate.

This is why it is vitally important that training for reactivity take place when the dog is "under-threshold", the point at which the problem behavior has not yet started. Often this means starting the training when no dogs are present, then presenting a dog from a distance at which the dog does not react. That distance is gradually decreased while the dog's tolerance to the presence of other dogs is increased and the dog is rewarded for good behavior.

This is where working with a professional trainer is so important. In addition to teaching you the obedience skills your dog will need, a trainer will teach you how to read your dog's body language so you can tell when your dog is about to react and keep him below that level. A trainer can also teach you what to do if you accidentally go too far and your dog starts reacting.


One of the first things most dog owners try when this behavior appears is some form of punishment. Punishment may vary from verbal reprimands to physical corrections. The vast majority of the time, this not only fails to improve the leash-reactive behavior, but makes it worse, as the dog's already negative association to strange dogs is now enhanced by the punishment or the overly-friendly leash-frustrated dog forms a negative association to other dogs.

Punishment sometimes appears to work because it stops the behavior in the moment. However, most dog owners find that the dog renews the behavior at each walk and, gradually, increases the frequency and intensity of the behavior.

The rule of effective punishment is that it completely stops the behavior after 2-3 trials. If the behavior keeps recurring, the punishment is not working. Temporary suppression of behavior is not changed behavior.

Punishment-based methods also require that the owner wait for the dog to exhibit the reactive behavior. Not only is the dog over-threshold and unable to learn at that point, but he gets to practice the behavior and the owner is now in a position of reacting to the dog's behavior

In the end, it is much easier to teach the dog what to do than what not to do.


Many dog owners have tried teaching the dog to sit and stay as another dog walks past. While I understand why this feels like a good solution - it is an attempt to get the dog quickly under control - the problem is that it often backfires, sensitizing the dog to the presence of other dogs.

Imagine you are walking down the street with a friend. Suddenly, a masked man with a bloodied chainsaw turns the corner and starts walking toward you. Your first reaction is to turn and run away from him, but your friend grabs your arm and pins you, yelling at you to quit being such a baby. The chainsaw man comes closer....and closer....and closer. Now you have an idea of what a reactive dog experiences when he sees another dog on a walk. Holding him still while the dog comes closer (even if the dog is on the other side of the street) only causes him to feel more unsafe.

If you do no training at all with your dog, turn and walk in the other direction when you encounter a dog on a walk (remember, before your dog start's reacting). This way, you have taken the lead, increased the distance between your dog and the other dog, and kept your dog safe.


The most effective treatment for reactive behavior, no matter the cause, is to follow these steps:

  1. Decrease stress

  2. Increase tolerance

  3. Teach and reinforce better behaviors

What those steps look like depends on each individual dog.

Decreasing stress could include replacing walks with training sessions for a while to take a break from practicing reactive behavior. It could including making changes in the home environment which could be exacerbating problems. For dogs with generalized anxiety, those that exhibit anxiety in multiple situations, not just on walks, it might include working with a veterinarian or veterinary behaviorist to explore the temporary use of anti-anxiety medication during the behavior modification process.

Increasing tolerance is the process of desensitization, exposing the dog to other dogs, or trigger, at a distance he/she can tolerate without showing signs of stress (under-threshold). Little by little, the distance from the trigger is decreased until the dog can tolerate their presence at a reasonable distance.

Finally, teaching and reinforcing better behaviors. Reactive behavior is what dogs do when they don't know what else to do. By teaching them what we want them to do, then reinforcing that behavior with something they love, we accomplish two things. First, we get a well-behaved dog that walks nicely by our side. But, more importantly, the dog begins to associate the appearance of other dogs with good things (counter-conditioning).


Reactivity is not an obedience problem. Dogs don't react to other dogs because they haven't learned to heel or stay. Learning basic manners is certainly beneficial and should be part of a behavior modification program, but it is not enough.

If the class is not specifically designed for reactive dogs, addressing the three components of behavior modification listed above, it is not likely to improve the problem...and can sometimes make it worse.

Stress affects learning. If a group class environment causes significant stress, the dog will not be able to learn or retain any of the lessons. Just as you would have difficulty learning a new skill in a room full of poisonous snakes, your dog will have difficulty concentrating in a class not carefully designed to reduce stress.


Many owners are tempted to use the dog park as a way to socialize their dog, to help them "get used to" other dogs. Unfortunately, immersing a dog in an environment with the thing they fear is like locking a child in the closet to help them get over their fear of the dark. I've worked with far too many reactive dogs whose behavior worsened after such an approach.

What we want our dogs to "get used to" is that other dogs are, at worst, neutral, posing no threat. This doesn't mean that some reactive dogs can't eventually make friends with other dogs on a one-on-one basis, but as always, it depends on the individual dog.

In the end, dog parks are for dogs that are already well-socialized to other dogs.


Reactivity is a common behavior problem most often caused by frustration or anxiety, both forms of stress.

The solution is to reduce the dog's stress through gradual desensitization and to change their association through counter-conditioning, while replacing the barking and lunging with alternative behaviors. Change does not happen overnight and will require some changes in your normal routine with your dog, at least temporarily.

Reactivity can be challenging and incredibly frustrating. But there are ways to manage and change your dog's behavior to make life much more pleasant for both of you. With the average life span of our dogs being 12-15 years, a few months of dedication can yield more pleasant walks for the rest of your dog's life


Schedule a free consultation to learn how I can help you with your dog's reactive behavior and other challenges in the Seattle area or remotely.

Copyright 2018 Lisa Mullinax. All rights reserved.

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