LEASH MONSTERS:  On-Leash Aggression

By far, one of the most common behavior problems that dog trainers are asked to address is leash-reactivity. The 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. Owners of these dogs become members of the Midnight Walking Club, changing their walking schedules to avoid other dogs.

Leash-reactive behavior does not discriminate by breed or background. This behavior appears in dogs purebred and mixed who were acquired as puppies from breeders and adopted from rescues.

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 leash-reactivity; the dog is reacting (or over-reacting) to something in the environment.


Leash 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 leash-reactive behavior.

Leash aggression 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 does it, the other dog goes away. He doesn't realize that the other dog probably lives two blocks over and is on the way home. In the dog's mind, his behavior effectively prevented a serious conflict.

There can be many causes for leash-reactive behaviors including lack of early socialization, a traumatic experience, or simply a lack of training.  Despite the claims of a popular television show, lack of exercise is NOT a cause of on-leash frustration or aggression. In the vast majority of leash-reactive cases, the dogs are walked regularly. In one recent case, the dog was being walked four times per day for over 45 minutes to an hour each walk. While physical exercise is just as important for dogs as it is in humans, it cannot solve behavior problems...in 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 dodgs..

Punishment sometimes appears to work, because it suppresses 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.

  obedience leash training
  A good training program will teach your dog to focus on you, without using the leash as a restraint or punishment, when other dogs walk by.

The most effective treatment for leash-reactive behavior, no matter the cause, is the gradual process of desensitization and counter-conditioning (DS/CC).

Desensitization is the process of exposing the dog to other dogs, or trigger, at a distance where the dog is "under-threshold" or not reactive. Little by little, the gap between the reactive dog and the strange dog is closed and the dog is rewarded for practicing an alternate behavior (taught separately, without dogs present). This puts the owner in control of the situation rather than reacting to the dog.

Counter-conditioning means to teach an alternate behavior in the presence of another dog.  This behavior usually includes walking nicely at a "heel" and looking at the owner instead of the other dog.

Working individually with a behavior consultant or trainer experienced in DS/CC methods is, by far, the best way to address your dog's reactive behavior. In addition to learning the DS/CC process, a behavior consultant "coaches" the owner through the process, teaching you the mechanical and observational skills you need to be successful and providing support throughout the process. An experienced professional will also be able to adapt the program to your needs and the needs of your dog.


While group classes can sometimes be a realistic goal for dog owners to work towards, they do not present an effective solution for the behavior, itself.  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.  Leash-reactive behavior often gets worse in a class environment, as it only serves to reinforce the dog's belief that other dogs present a threat.

Further, even the best of instructors must still divide their attention between all students, which does not provide the dog owner the individualized attention and instruction they need to work with their dog.


Even though this is a common behavior problem, it is frustrating and often embarrassing for the owner. Behavior modification requires a significant commitment on the part of the owner/s and is not remedied overnight. However, with the average life span of our dogs steadily increasing to up to 20 years in some cases, a few months of dedication can yield more pleasant walks for the rest of your dog's life.

Additional Reading

Understanding Aggression

Dog Training Methods

Dog Training Hearsay and Heresy


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