Dog/Dog Aggression, or Is It?

Christine Hibbard, CTC, CPDT

One of the most common calls we get from prospective clients starts with something like, “My dog is aggressive with other dogs, can it be fixed?” I’ve learned over the years that dog/dog aggression is sometimes in the eye of the beholder. The situation is further complicated because there are different types of dog/dog aggression.

Normal Dog PlayDogs playing
Sometimes, what an owner describes as dog/dog aggression is actually normal dog play. The way dogs play can seem scary to some human beings. These owners are overly conscientious about their dog’s behavior and his/her interaction with other dogs. While being conscientious about your dog’s behavior is a very good thing, like any good trait, it can be taken to an extreme. I sometimes wish I could wave a magic target stick that would make some overly conscientious owners worry less by transferring some of their worry and concern to owners who do not have enough of it. There’s a hilarious blog called Three Woofs and a Woo published by a photographer. She has wonderful shots of dogs playing.

Playground Bully
Some dogs never learned the manners of polite dog play society. They are like some people, just kind of clueless about how their behavior affects others. Jean Donaldson calls these dogs “Tarzans”. The most common sign of a playground bully is that the dog just doesn’t read cut off signals from their playmate. The other dog throws all kinds of body language that says, “OK, we’re done now, that’s enough play from you” and these bully dogs just don’t take the hint. Some dogs handle bullies quite well while others, well; they get a bit snarky when being mugged rudely by another dog who just doesn’t know when enough is enough. These dogs are rude, but not what we would call “truly dog aggressive”.

dog dog aggressionFear Aggression
Many owners believe that in order for their dogs to be mentally healthy, they must go to the dog park, or have social interactions with other dogs of some kind. This is not always the case. The reason that a dog is afraid of other dogs can stem from several causes. Some puppies were not exposed to other puppies during their socialization window. The socialization window is the first 18 to 20 weeks of a dog’s life and it’s the most important developmental learning period in a dog’s life. Puppies who never learned how to read other puppies’ body language and play cues can be afraid of other dogs later in life. Imagine if you lived at home with your brothers and sisters and never saw other children until you were 16 years old. When you finally left the house to go to high school, you’d probably be pretty uncomfortable around teenagers your own age, right?

Some dogs have had one or more traumatizing experiences from their interactions with other dogs. These experiences might have been terrifying, but not result in any physical damage. The damage comes in the form of fear of other dogs. When I see young puppies at the dog park being knocked down, run over, and played with inappropriately for their age, I cringe. What may seem funny or cute to the owners who think they are doing the right thing by “socializing” their puppy with other dogs inappropriately may be setting that puppy up for fear aggression around other dogs later in life. Its inappropriate to socialize a young puppy at the dog park where you can’t control the play interaction. If you have a puppy, find a Puppy Kindergarten that focuses on lots of supervised, off leash play with other age appropriate puppies. I’ve had clients call me because their dog was brutally attacked by another dog and now their dog is afraid of all other dogs. That’s the problem with fear; it has a tendency to generalize.

Leash Reactivity (aka Leash Aggression)Dog pulling on leash
I don’t like the term “leash aggression” because many of the dogs that react badly on leash by growling, barking, and lunging at other dogs are not aggressive. They’re reactive. You can tell whether your dog is exhibiting dog/dog aggression vs. leash reactivity by answering a simple question, “How does your dog play with other dogs off leash?” If your dog plays well at the dog park, but acts aggressively toward other dogs on leash, you have leash reactivity. If your dog displays fear aggression towards other dogs off leash, you have what most people call leash aggression.

Sometimes the most difficult cases for me to handle are the ones where the owners have never let their dog off leash around other dogs based on their reaction to other dogs while ON leash. I got a call from a woman who adopted a black lab mix from a shelter. Whenever she took the dog outside for a walk and encountered another dog on leash, she said her dog “was uncontrollably aggressive”. She had never let her new dog play with other dogs off leash because she was afraid of what her new dog would do. I decided to have a look for myself, or I should say I decided to let my dog Conner have a look for himself (see my colleague Greta’s post about Canine assistants for dog/dog fear & aggression). My dog Conner is absolutely amazing with other dogs. He just “speaks dog” with the most beautiful, calming body language that he throws at other dogs.

Dogs playing tugI had the owner stand with her dog on the sidewalk. I got Conner out of the car a block away. As we walked closer to her dog, I saw her dog put his ears up and rotate them out (sexy ears!) and then he started prancing and throwing play bows. As we got even closer, he starting barking hysterically and lunging on leash. Her dog wasn’t aggressive. He was leash reactive. He was so desperate to get to the other dog to play that he acted like a total lunatic. When I told the owner to drop her leash, I dropped Conner’s leash and totally appropriate and hilarious play ensued. It’s wonderful to see an owner cry tears of happiness.

We had some work to do with that dog, after all, while the owner was relieved her dog wasn’t dangerous, she still couldn’t walk him in the neighborhood acting like a total hysteric every time he saw another dog, but we knew what we had and could fix it relatively quickly. The way we treat leash reactivity and leash aggression can be quite different, but to treat it appropriately, we’ve got to know what we’ve got; hysterics, fear, or aggression?

Dog/Dog Aggression
Dog/dog aggressionWe do encounter what we call “true dog/dog aggression”, but it’s the most rare type of dog/dog aggression. Some dogs just find fighting with other dogs incredibly reinforcing. Other dogs, because of their breeding, or how they’ve been handled, or both, actually will kill another dog. This type of dog/dog aggression is quite rare compared to the dog/dog aggression that we see that is fear based.

These cases are difficult because of the time and resources that it takes to counter condition this behavior. Performing this type of work to help these dogs takes controlled environments, a great deal of time, and many, many stimulus dogs before we begin to see any effect. Often the cost and time are prohibitive and we’re left with two choices; the 3 Ms (a lifetime of Management/Muzzles/Medication), or euthanasia.

Do you have stories from your trips to the dog park that you’d like to share? Have you or are you dealing with leash reactivity? Tell us your stories or share your thoughts. We love to hear from our dog owners.


  1. says

    I have a pitbull very nice with people and small dogs runs up to everyone rubbing her head on everyone.We want to get a new dog but my dogs reaction around bigger dogs on the leash is scary. she jumps up and down whines she doesn’t bark. Im scared if we let her off she going to hurt another dog… When she was younger I gave a her a few play dates but she about 3 years old and hasn’t been around dogs for awhile. I have never let her off the leash with a dog bigger or the same size as her. She loves small dogs though.. what to do. Please email me back

  2. daishawn swafford says

    I have a pitbull mixed with bull dog very nice with people and small dogs runs up to everyone rubbing her head on everyone.We want to get a new dog but my dogs reaction around bigger dogs on the leash is scary. she jumps up and down whines she doesn’t bark. Im scared if we let her off she going to hurt another dog… When she was younger I gave a her a few play dates but she about 3 years old and hasn’t been around dogs for awhile. I have never let her off the leash with a dog bigger or the same size as her. She loves small dogs though.. what to do. Please email me back

  3. says

    This is a challenging issue for owners, and due to the risk of injury if you misjudge the situation, really requires the hands-on assistance of a qualified professional to assess and help you. If you’re in the greater Seattle-Tacoma area of WA state, please fill out our contact form at If not, we recommend consulting to find a qualified professional in your area.

  4. says

    We have experienced technical difficulties related to an overwhelming amount of spam on our blog. We believe the issue is now fixed and apologize for the delay in approving and responding to comments. We are working to respond to recent comments, but are unable to send private email responses. Thank you for your patience.

  5. Ruthless says

    Our one year old mastiff puppy is fine with 98% of dogs, on or off leash. But there are times when she is reactive and growls/advances on other dogs and we aren’t sure why. Is she afraid? Does she want to play and is provoking them into chasing her, as she does with our other dog. We took her to puppy social classes 3 x a week if not more from when we got her at 12 weeks until 8 months. We just finished our second tier of obedience. This happens off leash and on. It’s upsetting for the other owners, she isn’t trying to bite the other dogs but it looks bad because she is big. I always make her sit when she acts out-I try to correct the behaviour but it is so random I can’t tell what dogs will trigger this reaction. So no off leash privileges for now, and I spent the rest of the walk putting her in the down position when passing other dogs and wouldn’t let her return sniffs . It’s frustrating, I don’t want my dog to scare people.

  6. Alyssa says

    I can’t stress how useful our behavioural trainer has been for assisting us with our yorky x who has leash reactivity to the point that she would redirect it onto us… it’s been 2 weeks since we started the course and quite honestly, already the change is remarable. Our other dog, a staffy, is social with everybody, everydoggy and everything.. but I do have a question regarding some behaviour yesterday and something I’ve started to occasionally see.. whilst sniffing a new dog yesterday, she barked to say hello as she normally does.. that’s always been the case, but she also gave a little growl that, to me, sounded like she was uncertain of this new friend… yet she still wanted to play and did not snap at her… it was slightly different to a play growl though. The message I was getting was ‘I like you… but are we friends? or will you decide to snap at me?’ also, interestingly, when my dog decided that the best way to engage with this dog was to play with a toy, offering it to her new friend, (she finds this helpful when helping a fearful dog socialise)… her friend didn’t understand the playful growling and why she was doing that whilst offering the toy… it was like the other dog was afraid of playing? and maybe my dog was picking up on it? I’d be interested to hear people’s thoughts.

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