Why Does My Dog Act Like Cujo? Understanding Leash Reactivity

Why Does My Dog Act Like Cujo? Understanding Leash Reactivity

Picture this.

It’s a beautiful summer morning.  You’re out on the sidewalk, leash and poop bags in hand, enjoying a peaceful stroll with your dog.  It’s early, still cool and gray.  Quiet.  The very best time to be out, before the world around you is awake.

Your dog sniffs contentedly in the grass, finds a suitable place to pee.  Birds chirp.  A car passes, slow and lazy.  You glance up and down the street, ever watchful.  So far, so good.

You’ve nearly completed your loop of the neighborhood, allowing yourself to relax a bit.  Making the turn for home.  When suddenly – off to the side, not half a block away – you hear it.

The familiar creaking whine of a screen door opening.

A neighbor steps outside, oblivious, with her little dog on a leash beside her.

You tighten your grip instinctively, but it’s too late.  Your dog has seen them too.

He hits the end of the leash like an explosion, barking and lunging with a terrifying ferocity that shocks you every time it happens.  You call his name, tell him “no!” – jerking hard at his collar in a desperate attempt to make him listen, but it’s like you’re not even there.  The neighbor looks on in startled disapproval as you struggle for control and finally drag him towards home, a snarling mass of fur and flying saliva fighting you every step of the way.

Another walk cut short, another day begun with frustration and tears.  Once inside, you unclip the leash with shaking hands.

And the worst of it is, you’ll have to do it all again tomorrow.


If you’ve ever had a dog with leash reactivity issues, you don’t have to imagine this scene – you’ve lived it yourself, more times than you can count.

You know all too well what it’s like to take your walks early in the morning or late at night, choosing the most secluded route you can.  You’ve felt the frustration and embarrassment of making constant apologies for your dog’s behavior, and watching your neighbors clutch their pets closer and give you a wide berth when they see you coming.  Trips to the park or other public places are out of the question.

Perhaps you’ve watched other dogs on their walks, ambling along beside their owners, blissfully unconcerned with all the strange people and dogs around them.  Calm and friendly, enjoying the day.  Picture perfect.  And perhaps you’ve wondered, with just a twinge of guilt… why can’t my dog be like that?

The million dollar question.  Why, indeed?

As with so many things in behavior, there is no one simple answer that explains every case.  One thing I can say for certain is that it’s an incredibly common problem – and perhaps there’s some comfort in that.  Given the social stigma and embarrassment often associated with being the owner of “that dog,” it can be a relief to know that you’re not alone!  In fact, it might surprise you to know that leash reactivity is by far the most frequent training issue that I am asked to help with.

And really, in many ways, that’s the crux of the problem.

The truth is, leash reactivity isn’t really a training issue at all, like jumping on people or not coming when called – it’s an emotional problem.  These dogs may have a variety of different underlying reasons for their reactivity issues, but when they are snarling and lunging at the end of the leash, they all have something in common – they are truly, genuinely upset.  They are in a situation they don’t know how to cope with, and are doing the best they can.

Imagine being in a dark alley at night.  You’re alone.  Hypervigilant, aware of every sound.  If you happen to see a menacing stranger approaching, chances are good that you’ll scream, run away, or try to fight.  It’s also likely that if you were asked to recite multiplication tables at this particular moment, you would fail miserably – in fact, you might not even process the request.

How on earth can I do math right now, you think.  Your heart is pounding in your ears.  Your palms are sweaty.  This is a life or death situation.  I’m about to be attacked.

This is precisely how your reactive dog feels, every time you go for a walk.

It’s why he doesn’t listen when you tell him “no!”, or sternly command him to sit or heel, or anything else you may have tried.  He’s not ignoring you – he’s quite literally not capable of doing what you ask.  You can’t calculate 3 x 4 with a potential serial killer bearing down on you, even though I’m sure you know the answer.  And your dog can’t heel beside you while he’s barking hysterically at your neighbor, no matter how well-trained he is.

Knowing the answer is not the issue.  In order to follow instructions or recall simple things that we have learned, we first have to feel safe.

Not surprisingly, our dogs are no different.

For most of the reactive dogs that I work with, the world is a scary place.  Some are genuinely alarmed by every unfamiliar sight or sound they may encounter – everything from strange people, to umbrellas or flapping garden flags, to a box of recyclables on the curb that wasn’t there the day before.  Others have very specific triggers – they may react only to other dogs, or bearded men, or running children.  But all of them have decided (quite reasonably, from their perspective) that the best defense is a good offense.

And if you’re a dog, a good offense looks like this: barking, lunging, and snarling like a vicious wild animal, doing your very best to convince your adversary that you are much too big and scary to tangle with.  Even if the thing you’re afraid of is just an empty grocery bag blowing across the parking lot, the emotions underlying this impressive threat display are very real.

All right, you might say.  That’s all well and good.  But why is my dog so afraid?  What’s so scary about an unfamiliar person smoking a cigarette, or another dog on a walk with its owner, or an unattended bicycle leaning against a fence?

These things may be scary to your dog for a variety of reasons – all perfectly legitimate, from his point of view.

Remember that your dog’s perception of the world is a product of his past experiences (good, bad, or indifferent) as well as his genetic make-up.  In an earlier post, I wrote about a German shepherd named Heidi who was severely reactive to other dogs – in her case, the onset of her aggression could be traced back to a rather dramatic negative experience with a neighbor’s dog when she was young.  Other possible causes – less flashy, but just as important – may include a lack of adequate socialization as a puppy, or a genetic predisposition to fearfulness and reactivity.

Parsing the possible underlying causes of fear issues like this in any given dog can be complicated, and is a fascinating topic in its own right – but sadly, beyond the scope of today’s post.  Indeed, for rescue dogs with an unknown background or other dogs acquired as adults, we often have no idea of their history or what may have led them to develop their current issues.  The good news is, at the end of the day it doesn’t matter – the end result is the same, and so is our general approach to treatment.

So – with this in mind, what can we do to help?

Lots of things, as it turns out!  Leash reactivity is actually one of my very favorite behavior issues to work on, because treatment is usually a resounding success – most of the reactive dogs I’ve worked with have improved tremendously with a little time and effort, once a good training plan is in place.

I will go into much more detail on how we treat this problem in next week’s post, including a case study with videos and some specific suggestions you can implement yourself.  So if you have a reactive dog, stay tuned!  I hope that by the time you finish reading, you’ll have a much better idea of how you can improve life for both of you 🙂

9 thoughts on “Why Does My Dog Act Like Cujo? Understanding Leash Reactivity

  1. I have some leash reactive problems with my dog. But seems too random for me. Most of the time, (I would say 99%) is against male dogs of his size or bigger, small ones he doesn’t normally care. I have been training to reduce the reactivity and was working well. But there are times he just ignore the other dog passing by on the same side of the road, and even close to us (me and him), but sometimes he want to sniff the other dog (wich is actually his bigger compulsion), AND sometimes he passes the dog and start to react growling and barking. The funny thing is that when we are at a park and he is off leash, he usually ignore other male dogs, he just growling or barking if the male dog stay too close to him trying to sniff him. But if he was at the leash he would me reacting.
    I saw the same happening to a male puppy we already know, the puppy sometimes ask him to play, sometimes my dog give him attention and sometimes ignore. But as soon as the woman plug the leash on the puppy, he starts to react against my dog, barking and jumping on him trying to make him step back.
    This is something I really don’t get it. How a dog can be cool off leash, even with the dog close to him, but if it’s on the leash he react. And why one the leash sometimes on the road he simply ignore like the do, bg wasn’t even there, and sometimes he react like he was going to kill the other dog. It’s also funny that when smaller male dogs react against him, he act like he’s afraid and step back.
    I know that sometimes I got a like anxious because I’m expecting his reaction, and this may be reinforcing his reactivity, but also happens when I simply don’t care about the other dog. Sometimes I care and he ignores, and sometimes I don’t care and he reacts.
    It looks completely random to me.
    There was a time he was ignoring all the dogs that passes by us on the street, and I kept positive reinforcing him. But suddenly some weeks after he starts to react again.
    Since I rescued him from the streets, I have no idea how he was raised. He was something about 6 years old when I rescued, and now is a little more than a year since then.
    This is the only behaviour he has that I have no clue the reasons. Unfortunately sometimes we met other dogs on the road that I can’t get a safe distance to keep training well, and I know this can be a big problem to make training more consistent.
    (Sorry for english mistakes, isn’t my first language)

    1. Corrections:
      But if he was at the leash he would BE reacting.

      And why ON the leash sometimes on the road he simply ignore like the DOG wasn’t even there.

      I know that sometimes I got a LITTLE anxious.

      1. No worries, your English is just fine! 🙂 Thanks so much for sharing your story.

        Some dogs can be somewhat unpredictable as far as what they react to – this definitely makes training a bit more challenging, since we may not always anticipate when there will be a problem. There is usually a pattern from the dog’s perspective, but it may be hard for us to see what it is… the difference between a dog he reacts to and a dog that he ignores may be very subtle! Other times, whether they react or not may have more to do with their mood and what else has happened earlier in the day or on the walk – just like us!

        As to why many dogs are reactive on-leash and fine off-leash, this is also a common problem – it really deserves its own post, since the answer can be complicated. But in general, it’s because the leash restricts their movement and may prevent other, more appropriate ways of communicating – many dogs become more anxious on-leash because they are no longer free to leave the situation, while others become frustrated and upset because they are being held back.

        Thanks again for your comment, and I’m glad you enjoyed the post!

  2. I have been reading a lot of great information on leash reactivity recently but most of it seems focused on dogs who are scared and/or anxious about approaching dogs. One my my dogs very much enjoys the company of other dogs but flips over threshold into reactivity when seeing strange dogs. If we do structured introductions (with her muzzled just for safety) she does quiet well and we move past the muzzle stage quickly in most cases. Barking dogs and quickly moving dogs will push her over threshold as well.

    We have been working on self-control and connection games but are looking for more help. Perhaps BAT?

    So my question basically is, what if the issue is not fear?

    Thank you for your thoughtful and thought provoking blogs!

    Jen (and Puzzle)

    1. This is a great question! I had considered addressing it in the original post, but was afraid it might derail things and make the topic too complicated… I may do a separate post on this issue later on. There are some dogs who are essentially frustrated greeters, who become overly noisy and hysterical out of excitement rather than fear or anxiety – the underlying motivation for the behavior is different, but many of the same treatment approaches are still effective.

      Next week’s post will go into more detail about how we work with these dogs, and I think it may still be quite helpful to you! Basically, with dogs who are reactive to other dogs for any reason, we start at a distance where they are able to be calm (this may take a lot of distance for some dogs, at first!) and mark and reward every time they look at the other dog. For fearful dogs, this is quite valuable because of the classical conditioning at work here – associating good things with seeing another dog.

      But there is also an operant component to this approach – ideally, if your timing is good, you are marking and rewarding before your dog has a chance to start barking, lunging, etc. Most dogs will fairly quickly progress to the point where, if you withhold the mark and reward for a second or two, they will begin to look expectantly at you when they see another dog. At this point, you can begin to mark and reward the choice to look away, rather than the initial “noticing” of the dog – hope that makes sense! Once they’re good at this, you can gradually move closer and work up to allowing a greeting if you wish, as long as your dog is calm and under threshold.

      1. We have gotten to that point with unseen barking dogs but have not progressed beyond that yet. I will certainly read next week’s posting and look forward to a Frustrated Greeters post in the future!

  3. I over 30 years of having dogs of all types and sizes and personalities and backgrounds, I have never had a leash reactive dog. I have had dogs that were 100% aggressive to other dogs and animals in all situations, but never one that was strictly leash reactive.

    Also, as a person who walks dogs everywhere including off leash parks and open space, I have seen many people with reactive dogs behind fences and on leash. I have zero empathy for them because 99.9% of the people I see do absolutely nothing to tell their dog what they are doing is wrong. They think it is cute and natural and that “the dog is just having fun.” They like it and let it happen. I have even seen packs of dogs behind fences bark at my dogs as I walk by and the owner is on their cell phone or chatting with their friends.

    Very frustrating, so you can see that I don’t think is a Dog problem. It is a people problem.

    1. I definitely agree that many times, people don’t feel that this is a serious issue, particularly with small dogs. And unfortunately, this is quite unfair to the dogs in question because it’s not pleasant to constantly feel so threatened by everything around you! Very much the opposite of having fun, but you’re right – many owners don’t think of it this way.

      A great many things in the world of dog behavior are actually “people problems”, rather than dog problems… it’s important to get both members of the team on board (dog and owner) to make progress on anything 🙂

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