Causes and treatment of dog on leash aggression

Barrier Frustration can occur if a dog is behind a window, fence, or on leash and is not allowed to interact with the environment. After a while, she may get frustrated and aggressive. One indicator of Barrier Frustration having a part in aggression is if a dog barks behind barriers and is calm around dogs when off-leash, but is very aggressive behind a barrier or on-leash. Dogs, of course, can also show aggression no matter how much they are being contained as well.

From my experience, Barrier Frustration is one of the major causes of on-leash aggression. Dogs can show aggression towards people or dogs or both. Whenever you see a dog barking uncontrollably behind a window or a fence, this is most likely the result of either improper socialization or barrier frustration, or both. What has happened over a period of time is that a dog gets extremely frustrated, (that is why it is called Barrier Frustration) and the appearance of the dog or person results in anxiety and eventually aggression. Other signs of Barrier Frustration are "fence tracks" that get formed by a dog running back and forth behind a fence.

When a puppy initially is in this situation, she might want to say “hello” to all the dogs passing by. But, a  FENCE or WINDOW is blocking her way. Then you take her for a walk, and the leash prevents her from getting to what she wants. Ugh! Day after day of wanting to interact with no payoff continuously gets her more and more frustrated. Maybe she eventually gets taken to a dog park and she has so much pent up desire to play with dogs that she barrels into the first dog she sees. Then her person takes her home and says, “Well, I can’t take her to the dog park because she is aggressive” and then the situation gets worse because she never gets to interact with dogs. On walks her guardian crosses the street, she never goes to dog parks, her socialization skills deteriorate or never get formed correctly.

barrier_frustration1Questions about socialization?
Improper socialization or an unknown history of a newly-adopted older dog can contribute greatly to on-leash aggression as well. Dogs that do not feel confident about greetings, yet so WANT to greet often reach a point in the greeting process where the situation moves into unknown territory for them. Maybe the other dog is moving too quickly, there are too many dogs approaching, they are cornered next to a wall, etc. A more confident, well-socialized dog can handle more before becoming reactive, and can escalate her behaviors more slowly and remain under control. Socialization is key.

Does any of the above sound familiar? Want to avoid these scenarios? Here are some steps for you to follow.


As with all behaviors, if the behavior is allowed to go unchecked, it will feed on itself and escalate in intensity. Here are some strategies to counteract the frustration.

If your dog is barking, you have three options; either practice one of the two training strategies outlined below, or remove her from the location and manage her behind a baby gate or in another room. You can also block her view, if possible, by lowering blinds or using another physical barrier.

Three Treatment Options

If you have time for a training session, I recommend one of the following strategies.

  • Desensitize her to the movement.
  • Call her every time she barks. If the barking intensifies, switch to a management strategy.
  • Manage her location. Management means you should move her to an area of the house or bring her inside away from the trigger that is causing her to bark.

barrier_frustration2Desensitize a Dog to Stimuli

The key is to keep her stress level under control. If you are not able to work with her, manage her so she is not able to see outside of the house or run along your fence barking repeatedly. The key with desensitization is that your dog has to be comfortable the entire time. If a dog appears and she barks each time, then behaviorally her brain tells her that the current pattern consists of a) I see a dog and b) eventually I will bark. If you do not treat the anxiety, what can happen is that the anxiety can increase because she is getting anxious about the prediction of getting anxious. In other words, she knows that she will get anxious when the dog gets 30 feet away, for instance, so over time she will get anxious when the other dog is 40 feet away because repeated exposure has resulted in her anxiety, and now the dog is coming closer. 39 feet, 38 feet, 37 feet, . . . Oh no! Get away! Bark!

barrier_frustration3In my private dog training business I usually get calls to hire me for this behavioral problem because of a specific event such as a dog “biting out of nowhere” or “my dog sniffed, paused and then attacked another dog”, or “she used to be fine with dogs but now she barks at them when they are a block away”. My first question is always to find out if their dog barks out of the window or behind fences. In hindsight, my client can usually identify a pattern of increased barking leading to the event that initiated their call for dog training help.

I want you to avoid having to spend money on training and I want you and your dog to be calmer and happier.

Desensitization Steps

  • Have your dog on leash so you can gently move her away, if needed.
  • Watch her head for signs of orientation towards movement outside the window or on the other side of the fence
  • AS SOON as she sees movement outside, click and treat
  • If she does not take the treat, move her farther away from the window and try again at the new distance
  • Ask friends to walk back in front of the house, with and without dogs
  • Eventually you will notice that she doesn’t tense up immediately. That is when you should start talking to her, “Good girl, you are doing great, there is a dog outside . . . . “ and then Click and Treat
  • You are trying to get more duration of the event between marking the time with the clicker
  • As always, each 'click' results in a treat

Come When Called – Incompatible Behavior

You can teach an incompatible behavior such as Come When Called to counteract the escalation of Barrier Frustration. It is called an incompatible behavior because a dog can't do both behaviors. A dog can’t be anxiously barking out of the window if she is running towards you. So, you can ask her to “Come” every time she barks. What happens over time is that the appearance of the trigger outside, which used to cause barking, can cause your dog to predict that you will call her.

This lessens the intensity of the barking, and with enough practice, can also teach your dog to come find you instead of barking. This is actually one way that service dogs are taught to help clients that are hard of hearing. A dog can be taught to find their person when the doorbell rings. Very helpful if you can’t hear the doorbell! Dog training is so much fun!

Come When Called

  • Each time your dog barks, call her to you and then reward
  • Use a leash to gently pull her to you and reward -- you don't need to jerk your dog. You can also try tapping your leg or moving away
  • You are NOT rewarding barking, you are rewarding the incompatible behavior, in this case she is coming to you


  • Wait for “hot times” such as when people are walking their dogs after work and just get ready to work on either of the above exercises
  • If your dog is barking more than 2 times and you don’t have time to work on one of the above exercises, prevent her from gaining access to the window
  • Don’t get frustrated, it will work out
  • Get your dog off of a choke chain or prong collar. I never like these, but when dealing with anxiety or aggression, they can make the problem worse. 

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