Dealing with Dog Sibling Rivalry

Just like people, some dogs really struggle with sibling rivalry. In fact, dogs that go home with their siblings often struggle with aggression issues more than dogs who are raised without a “sibling” – whether or not they’re actually related.

In the latest “Ask a Trainer” question, we’re helping a reader troubleshoot the sibling rivalry between his two teenage dogs.

Our reader writes,

How do I stop my two pups from fighting with each other? They are brothers and have been together since birth. They are normally very well behaved but have recently started fighting with each other to the point of drawing blood. They are not quite a year old and we are obviously still in training mode. They know all of their basic commands and are fully house trained using a bell to ask to go outside. Any advice would be greatly appreciated as I am at my wits end.

Dealing with dog-dog aggression and sibling rivalry isn’t easy. Get the help that you need with a Certified Dog Behavior Consultant in your area. If there’s no one near you, I can help.

I offer 15 minute behavior help calls1 hour calls, and month-long email support packages to suit your needs, no matter where you live.

Having two dogs that fight with each other is incredibly stressful for a home. Unfortunately, dog-dog aggression is often worst with dogs that are the same gender and the same age. Things can be even worse when the dogs are siblings.

What’s Littermate Syndrome? Does It Exist?

Anecdotally, it seems more common for pups (related or not) who are similar in age and raised together to become aggressive towards each other as adults. Sometimes, they also become so emotionally reliant on each other that everything else is SCARY.

This phenomenon is commonly termed “littermate syndrome,” but there’s actually no research to show that littermate syndrome exists. In fact, breeders commonly raise siblings together with no problems.

I recently did a lot of research on so-called littermate syndrome for the above-linked IAABC Journal article. I’ll quote liberally from that piece here:

“My personal hypothesis is that perceived littermate syndrome is actually generally a result of several specific conditions that often arise when people attempt to raise siblings together. Of course, all of these observations are, by necessity, anecdotal and based on personal experience.

  • Inadequate socialization, especially with other dogs. Many unknowing owners assume that letting their two puppies play together is an adequate replacement for dog-dog socialization. This misunderstanding is particularly understandable when the two puppies are the same age and breed. In other words, it’s particularly easy to fall into this trap when raising siblings. The owners I personally know who have successfully raised sibling pairs took pains to introduce the puppies and teenage dogs to other dogs, both together and separately.
  • Inadequate environmental management. It also seems that some owners are more likely to slip up on environmental management (removing food bowls, managing access to resting places) when the dogs are perceived as “best friends who have never been apart”—as is the case with siblings.
  • Insufficient “alone time” training. Many of the hyperbonded dogs I met at the shelter were crated together, walked together, taken to the vet together, and so on. The owners sometimes reported that they had “never been apart.” And therein may lie the problem. Just like we’d expect to see separation anxiety if a dog had never been more than three feet from their owner, it’s not surprising to see extreme distress in these adult siblings that have never been taught how to be apart. I’ve found that most of the owners that successfully raise and keep siblings do things with those dogs. They go to training class, shows, trials, and more with just one dog at a time. At the very least, the dogs are used to being trained and crated separately.
  • Failure to meet the dogs’ needs. Many of the cases of sibling aggression that I’ve seen are also paired with a clear lack of mental and physical enrichment for the dogs. In conversations with the owners, I often realized that they assumed that the two siblings could keep each other company. The owners didn’t see a need for puzzle toys, training games, long walks, and so on because the dogs have each other.”

In other words, no, there’s not a diagnosable syndrome for littermates. We can’t open up a pup’s brain and point to the problem.

But humans who raise two similarly-aged puppies together often make similar mistakes that lead to specific behavior problems (like sibling rivalry, aggression, or whatever you want to call it).

Why Are We Seeing Problems Now?

Dog aggression generally starts to manifest around 8 to 20 months of age – when dogs are teenagers.

All of this is to say that our writer is dealing with a tough situation. Sibling aggression is a common phenomenon in dogs, and is incredibly difficult to deal with. Unfortunately, good training alone won’t prevent this problem. Your dogs can know all sorts of cues and tricks and still have issues with aggression.

There’s a basic framework for helping dogs that fight with each other if they live in the same home:

  1. Separate the dogs completely for now. This might mean a “crate and rotate” setup where one dog is in the crate (or in a separate room) while the other is free, and vice versa. This keeps everyone safe starting right now.
  2. Identify what caused the fights. Now that you have a bit of space to think, it’s time to identify the “triggers” in your dog’s fights. Common triggers include food, toys, attention, sleeping space, doorways, or exciting things outdoors (like squirrels or visitors).
  3. Start muzzle training the dogs. Be sure to get a comfy basket muzzle that fits your dog (see our muzzle fit guide here). I use extra-tasty treats that are easy to get through the bars of a muzzle (explore our favorite muzzle-friendly treats and check out our demo on how to give treats through a muzzle). This will allow you to start reintroducing the dogs with maximum safety for the dogs.
  4. Teach both dogs hand targets and go to mat behaviors. Do this separately and ensure that the dogs can easily “relax on mat” and “target” while there’s food or toys on the floor before you start introducing the cues to social situations. Read more about “proofing” behaviors here to ensure that you build up the difficulty of training properly. This allows you to separate the dogs without putting your hands in danger. Pulling the dogs apart can also add tension to a situation, which can actually cause a fight!
  5. Reintroduce the dogs in neutral situations. Take the two dogs on walks together (the parallel walk method is great for his) and do other things where the likelihood of a fight is extremely low. This allows the dogs to continue having good experiences with each other. Practice hand target and go to bed behaviors while both dogs are feeling relaxed and happy. Continue avoiding triggers whenever possible.
  6. Use counterconditioning and desensitization to help the dogs relax. Pick a single trigger and tie both dogs down to a door. Have them lie on their mats. Then reintroduce a trigger at a low intensity. For example, put a food bowl down far away from both dogs. Then feed both dogs copious amounts of chicken and other yummies. This way, they learn that Brother + Trigger = Chicken. This will help them learn to relax. This is pretty tricky to do well, and I highly recommend getting the help of a Certified Dog Behavior Consultant.
  7. Use hand targets and go to mat behaviors to split up the dogs if needed. Practice sending the dogs away from each other to their beds around their former triggers. Try your best to avoid triggers unless it’s a training situation (this is called management) and don’t be afraid to call the dogs apart before things get tense. So if you see Fido giving Rover the stink-eye, call them apart before things get nasty.

Unfortunately, not all dog-dog aggression cases resolve nicely. In many cases, it’s actually best for the dogs to rehome one of them. This allows the dogs to live full lives without constant management, crating, and squabbles.

Many dogs that fight with their siblings are perfectly friendly to other dogs. Some are even friendly and playful with their siblings in moderation, but not 24/7 (this may sound familiar to those of us who love our families but cannot imagine moving back in with our siblings).   

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