Are Two Pups Better Than One? Insight on Littermate Syndrome

Littermate syndrome is the term given to behavioral issues frequently seen when two pups of a similar age are raised together.  It most often occurs when two pups from the same litter are adopted by a family, though it can also be seen when two unrelated pups are raised together.  Interestingly, significant behavioral science studies have not been conducted on this issue.  However, the anecdotal evidence is compelling.  Professional trainers, veterinarians and responsible dog breeders are well aware of the prevelance and gravity of this all too common issue.  

While it may sound ideal to raise two pups together, allowing them to become close friends, it’s actually far from it.  Having multiple dogs can be a joy, and a major plus for the their quality of life, but it is best for each of the pups to be at least 6 months apart in age.  When young pups are raised together, their relationship with each other hinders their social development and also prevents the essential bond between the pup and his humans from fully forming.  Although littermate syndrome doesn’t develop every time two puppies are raised together, it is common enough that we strongly advise against getting two puppies at the same time. In our experience at What a Great Dog, where we work with thousands of dogs every year, RARELY do two pups raised together reach their full potential.  It is far more common that serious behavior issues develop in one, or often both, pups. 

Behavioral Issues Associated with Littermate Syndrome

From a young age, the two puppies form a very strong bond, learning and feeding off of each others emotions. That exclusive relationship seems to stunt both puppy’s social development. This typically leads to behavioral issues in one or both of the dogs.  Those issues include some or all of the following:

  • Leash Reactivity
  • Frequent fighting between the two pups (often resulting in injury) 
  • Fear of strange people and/or dogs, often leading to fear aggression
  • Fear when encountering new situations when alone
  • Less than ideal training outcomes, as the pups devalue their relationships with humans

Even when these issues aren’t seen early on, they will often intensify as the pups develop toward maturity.  Fear and aggression are seen in littermates raised together even in breeds that are not prone to aggressive behavior. 

Littermate syndrome can sometimes be managed, but it is a lot of work.  Working to prevent littermate syndrome will easily result in 2 – 3x the workload of raising a single pup properly.  It’s also important to highlight the fact that once one or both pups are experiencing these issues, simply separating the pups will not solve the issues.  The serious behavioral consequences can be lifelong.  While behavior modification can be effective.  It is a long road that not all families are in a position to take on.  

When counseling families on this issue we’ll often hear “If this is such a big problem, why didn’t the breeder tell me about it?  She encouraged us to take two pups so they could be best friends!”  There are two reasons why this happens.  First, breeders are motivated to place puppies.  Selling two pups in one transaction is tempting.  The second reason is that most breeders are not experts in dog behavior.  They have litters and sell the pups, then move on to the next litter.  There are highly responsible and educated dog breeders.  Breeders who are well educated on dog behavior refrain from placing two puppies in the same home.    

How to Avoid Littermate Syndrome

The easiest way to prevent littermate syndrome is to only take one puppy at a time.  It is always tempting to take two because they are super cute together.  And, it seems like things will be easier because “they will entertain each other.”  But an important piece of preventing littermate syndrome is to largely keep the pups separated, allowing very limited time to play together.   Having two dogs who are young and energetic at the same time is a good idea, BUT it’s essential that you wait at least 6 – 9 months after getting the first pup before adding a second one to your family.  We feel so strongly about this that we regularly counsel families with littermate pups to consider rehoming (or returning to breeder) one of the pups.  This is especially the case if we are already seeing behavioral issues.  Returning a 12 week old pup to the breeder may be difficult.  But trying to rehome an adolescent dog with serious behavior issues is beyond difficult and heartbreaking.  

I have Two Puppies and I Need to Keep Both

If you already have two puppies and are intent on keeping them together, then it’s critical that you form a solid plan. The main things you’ll want to achieve are confidence and good social behavior in each of the pups both when they are separated from each other and when they are together. The key is to ensure that both pups individually have all the necessary positive social experiences while they are still in their critical socialization period (under 16 weeks).  

Each pup will need daily, individual outings, without the other puppy, where they are exposed to new environments and see strange dogs and people.  The goal is to individually socialize each pup to new experiences, as they learn to rely on their person and not the other pup.  Just like when raising any pup, it will be important to expose them to the things they will likely encounter throughout their lives, like: people with different characteristics (different ethnicities, beards, sunglasses, hats, canes, walkers, etc.)  They also need to see a wide variety of dogs.  Ideally, the pups aren’t greeting all the people and dogs they see, but instead getting good passive socialization from a bit of a distance. 

Group training classes are important for all pups, but essential for littermates being raised together.  Each pup should be in a separate class.  This will be key to developing a strong bond between the pup and his people. 

Only after each pup is showing healthy social behaviors and has a solid start on training should you start training the pups together.  A great exercise is walking the pups together, each with a different handler.  Walk for a bit, then split into two different directions.  The pups should be highly rewarded for going with their handler away from the other pup.  Practice training with the pups at a distance, but in sight of each other.  

When you crate the dogs make sure that you utilize an individual crate for each dog and never crate them together. You can start off with the crates right next to each other to ease their separation from their litter.  But as soon as the pups are comfortable with that arrangement, start moving the crates farther and farther apart.  Ideally, the pups should be crated in separate areas of the house within a week or two of coming home from the breeder.   

With hard work, littermate syndrome can be lessened.  But, the steps need to be taken very early, ideally the first day the pups are removed from their litter.  Certainly, avoiding the issue is the very best plan for both the dogs and the family. Having two dogs of a similar age is fun and has clear benefits.  Just remember that both your life AND the dogs’ lives will be best if you avoid temptation and space those adoptions apart by at least 6 months. 

Maureen Patin is a Certified Professional Dog Trainer with over 15 years of full-time professional training experience.  She is the Founder and Head Trainer of What a Great Dog! Training Centers.