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Inter-dog aggression

A few years ago when I started Evolution Dog Training I made a promise that I would  continue my education concerning my professional dog training business. Always learning, always expanding my knowledge means I am able to help the local dog community evolve. I started out much like ever other new trainer, teaching basic obedience classes which I LOVED! From there my direction shifted to working with more & more dog reactivity. Once I began learning all that I could about dog reactivity, it opened another world for me; Behavior. I was hooked. I recently became an  Associate Certified Dog Behavior Consultant through the IAABC. I want to help people fully understand their dogs and show how the "little things" affect our dogs. This year I have been receieving more calls regarding same household dog-dog aggression. I know it can be so difficult when dealing with "aggressive" type behaviors from our dogs. Biggest thing I want you to know is, you are not alone. In the meatime, maybe the following will help you understand what could be driving  your dog's behavior. Take a look with a new perspective. 

When dealing with inter-dog aggression, we need to pay close attention to the dog’s social structure/environment with each other. (I must point out that humans are not dogs, and therefore, it is POINTLESS to assume the “alpha role” to earn your dog’s respect.) The dominance myth has long been debunked, and the latest studies suggest that dogs are in fact NOT status seeking animals attempting to take control over your home. Instead, our dogs are opportunists that will do whatever behaviors are reinforcing to THEM. This is true for us humans as well.


Please join me while I briefly explain how the little things can affect your dog’s social structure with one another. If you are experiencing inter-dog aggression in your home, please seek a qualified canine behavior professional. Check out IAABC (International Association Animal Behavior Consultants) @ for a directory of certified canine behavior professionals in your area.



Within our dogs social hierarchy there is usually one who is “high ranking” and one who is “low ranking”. This is not to be confused with obnoxious, fighting type behavior from the high ranking dog. A true “high ranking” dog will not get into scuffles, simply because they do not have to! A real high ranking animal would normally be tolerant of lower ranking members. You might be surprised to learn that the behavior from the lower ranking members towards the higher ranking members is what determines the social hierarchy. In other words, by “withdrawing”, lower ranking members make the hierarchical status clear. (Dr Karen Overall)


To begin, let’s look at resources and how they affect the social hierarchy between dogs. The “higher ranking” members are the ones who regulate & maintain access to some resources, HOWEVER, such access is contextual. A certain resource may be highly maintained at certain times when at other times it is not, or other resources may not be maintained at all.

This means resources can be both contextual and subjective.


Some common resources from our dogs pov are as follows (in no particular order)


Attention- Owner/ Guests (greeting the owner & interacting)


Food- Always think SPACE when feeding dogs. Use a crate individually for safety.


Toys- Especially new ones!


Sleeping areas- A favorite spot, a high spot, or a favorite bed


Bone/Rawhides/Bully sticks- These in particular are seen as a high value resource even among dogs that get along well. Always practice caution.


Space- Everyone has a space threshold, that invisible barrier that if surpassed may yield a dispute. Our dogs are no different. The majority of dogs have varying degrees of space thresholds.


Keep these in mind when deciding to add another dog to your home. Set up the environment so everyone succeeds.


Generally, the high ranking dog will maintain access to a resource through a ritualized display, HOWEVER, problems start when such displays are no longer effective. This is why we often see fights in dogs of similar or equal rank when those displays are ignored.


Tension over resources is a common trigger. Remember, resources include more than just food; a human can be a high value resource, along with the best seat in the house, or getting out the door first. The dog could even be anxious over the possibility of losing possessions. Sometimes a signal is missed by the other dog. This is why both dog's social skills, and history matter.

If a dog has not learned how to properly speak dog, or never learned the rules of canine play, misunderstandings can happen quickly.

Yes, your dog’s early interactions or lack thereof matter. Dogs who do not receive proper socialization & interactions as young puppies can lack the skills to navigate as a dog should.


Other triggers may be less obvious. A dog who is in pain rarely expresses that pain, the mere proximity of the housemate who has inadvertently bumped her in the past could be a trigger. The undiagnosed arthritic dog may become defensively aggressive in anticipation of being hurt by a livelier canine pal, trying to prevent a painful contact. This can often appear to be “unprovoked” aggression.


Next we want to address how high arousal levels can affect our dog's relationship.

At times our dog’s social boundaries can be blurred by events. Example, if two canine housemates have not seen their owner for a long time, the lower ranking dog may not defer to the higher ranking dog, blocking access to the owner because it cannot contain its excitement. When over excitement takes place, this is often a trigger for big fights to occur among multi dog households. It is easy for the excitement to blur social rules/proper etiquette causing a fight to erupt. Play is another one that raises arousal levels, blurring the line & leading to a fight breaking out. It is always best to train your dog to take a break during play. Most dogs play, play, play and play... This is not ideal. Each interaction is raising their arousal levels to a dangerous high, lowering each one's threshold. Ends up looking like this; Play, Play, Play,Play, Play.... FIGHT!!!! Some dogs have to be taught to stop playing, Teaching your pup to take a break is absolutely necessary. I like to use long lines in case I need to assist the dogs to recall away from one another.


Start interrupting your dogs play, recall & reward them for taking a break. Do a few repetitions of sit, down, stay (if they know this one) when finished say “all done” and walk away. This is a great way to help your pups learn to break play from one another on their own. Plus it brushes up on their obedience cues. Do not over do this. You do not want to build frustration between your dogs. Short sessions throughout the day are better than training for 40+ minutes at one time.


Now, word of caution, when we interrupt our dog’s behaviors we must be aware of something called “redirected aggression”. Highly aroused dogs go into a hypervigilant state that triggers a reactive response which would not take place in a normal setting when the dogs are calm. Think about two dogs behind a fence, (I’m sure we all have witnessed this) they can be calmly hanging out, until a dog/person walks by causing the two dogs behind the fence to erupt. Next thing you know the two dogs behind the fence have begun fighting with each other. That’s redirected aggression. Because of this, owners of dogs who fight should never physically get in the middle of the two dogs who have a history of fighting. You could get literally caught in the middle. And we do not want that!



How changes within the social structure begin, a typical scenario affecting social hierarchy takes place when the “high ranking” dog starts becoming weak/older. A younger dog that has reached social maturity may, therefore ignore the ritualized displays of the older dog which may elicit a serious fight. This is where BOTH of your dogs need your assistance. Do not allow the younger dog to harass the older one. Keep their play sessions short n sweet. Make sure each dog has their own space. The same way we modify our environments to meet our needs, we should also be willing to modify our dog’s environment so that their needs can also be met.


Which brings me to the next “little thing” that plays a role in your dog’s social structure, STRESS. Sometimes, aggression among two dogs occurs as a result of trigger stacking. Trigger Stacking is when a dog (or human) experiences “small triggers”, these accumulate over time causing the dog to sometimes appear as if he “attacked the other dog out of the blue”

Each trigger causes a reduction in the dog’s patience level for the day, and when they all stack up in a short amount of time, the dog “lashes” out (think the straw that broke the camel's back).




Moving on, let’s discuss multi female dogs households, studies show female/ female dog homes have a higher percentage of fights versus male/male dog homes. Having two female dogs in the home can be like a double edge sword; two females close in age, you think “aww they can grow up together” except that when two females are close in age there is often a lot of competition (from their pov).

On the other side of the sword; adopting a younger female while owning an older female can also be a risk. The new dog will have more energy that may affect the dynamic between them. They may fight over several competing elements. Such fights seem to occur the most in the presence of the owners.


They may begin fighting over (resources); sleeping areas, food, toys, & owners etc. And sometimes, a cause may not be completely “visible”. Keeping a training journal for this reason is highly recommended. This will help identify your dog’s triggers. I have clients list them in order of greatest to least. Once the triggers are identified, you will need to manage your dog’s environment to reduce trigger incidents and minimize conflicts. In addition, setting up an indoor camera that records to an SD card to review for behavior patterns that you may otherwise miss.


A big role is played by you, the owner. It is up to you to set the stage so to speak. I highly recommend setting it so that you all succeed. You can do that by being diligent when it comes to your dog’s behavior. Work with a certified trained professional. You will need to learn to read and UNDERSTAND your dog’s body language so that if something looks like it’s more than just a minor disagreement you are able to confidently intervene. Using methods like management, desensitization & counterconditioning a lot of progress can be achieved at maintaining a harmonious social relationship.


Special note:

Keep both dogs separated when you cannot actively supervise them. (Managing the environment)

Change the stressor (other dog) from negative (bad thing) to positive (good thing) .

Strategy to apply: Change the “aggressive” dogs perception of the stressor using DS/CC (Desensitization/Counterconditioning).


A critical component to a successful behavior modification plan is that you manage the environment to decrease your dog’s triggers as much as possible. If the dogs are allowed to engage in fighting, tension between your dogs will continue to rise; the more they practice/rehearse those unwanted behaviors the better they get at fighting (think professional boxers) and hence, the longer the behavior modification process will be. Behavior change is not something that happens overnight. Your dogs didn't get to this point overnight so it certainly will not go back to “normal” overnight. You are going to have to put in the work. And guess what? It will be a new “normal” and that’s okay, that is what we want. In the past your dogs were not living their best life. After you put in the behavior modification work, you are giving your dog(s) a chance at a new life. A better life, one according to them.



Kimberly Combs, ACDBC

Evolution Dog Training


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