Understanding Littermate Syndrome in Dogs: What It Is and How to Prevent It
- Alex Dondeville
- May 15
- 4 min read
Understanding Littermate Syndrome in Dogs: What It Is and How to Prevent It
Bringing home a new puppy is an exciting milestone—but what happens when you bring home two? While the idea of raising siblings together may sound ideal, it can sometimes lead to unexpected challenges known as Littermate Syndrome.
In this blog post, we’ll break down what littermate syndrome is, why it happens, how it affects dogs, and what you can do to prevent it—whether you're a breeder, rescuer, or pet owner.
What Is Littermate Syndrome?
Littermate Syndrome is a behavioral condition that can occur when two puppies from the same litter or puppies of similar age raised together form an unhealthy bond. Littermate syndrome can occur in any situation of two puppies under the age of two years old. Rather than bonding and socializing with humans or other dogs, the pups become overly dependent on each other. This co-dependence can interfere with their individual development, leading to a range of behavioral issues.
*Important note: Not all pairs of puppies will develop littermate syndrome, but the risk is significant enough that trainers and behaviorists often advise against raising sibling puppies together without careful management.
How Littermate Syndrome Happens
Littermate syndrome begins during the critical socialization period of puppy development (around 3 to 14 weeks of age). Puppies rely on their littermates to learn bite inhibition, social cues, and communication. However, when siblings are kept together past this period without proper separation and individual socialization, they may begin to:
Depend on each other for comfort and security
Struggle to focus on humans or training
Show increased anxiety when separated
Fail to develop their own identities or confidence
The presence of a sibling can dull the puppy’s drive to interact with humans or explore independently. Instead of learning to cope with new experiences alone, they rely solely on each other, stunting emotional growth.
Signs and Symptoms of Littermate Syndrome
Every dog is different, but common signs of littermate syndrome include:
Extreme distress when separated – whining, barking, pacing, or destructive behavior
Failure to learn basic obedience commands
Fearfulness or anxiety around new people, places, or other dogs
Aggression toward one another as they mature
One sibling becoming shy or withdrawn while the other is dominant
In many cases, the symptoms worsen over time if not addressed. The emotional reliance can result in stunted development, poor training outcomes, and even reactivity.
How Littermate Syndrome Affects Dogs Long-Term
If left unaddressed, littermate syndrome can severely impact a dog’s quality of life. These dogs often become:
Inflexible and fearful in new situations
Difficult to train without the presence of the sibling
At risk for separation anxiety disorders
More likely to display aggression or reactive behavior in adolescence or adulthood
In most cases, professional intervention from a certified trainer or animal behaviorist is necessary to address the root problems. Mark the Spot is dedicated to helping littermate syndrome puppies, if you think you or someone you know has dogs experiencing littermate syndrome or any symptoms please contact us.
How to Prevent Littermate Syndrome
Preventing littermate syndrome starts with awareness and planning. Here’s how you can avoid the risks:
1. Consider Adopting One Puppy at a Time
This is the simplest way to avoid the problem altogether. Raising one puppy allows for full focus on training, socialization, and bonding.
2. If You Adopt Siblings, Create Individual Identities
If you're committed to raising littermates, it’s essential to treat them as individual dogs. That means:
Separate training sessions – Train each pup alone so they learn to focus on you, not each other.
Crate them separately – Each should have their own safe space to rest and sleep.
Walk them separately – This encourages confidence and independence.
Socialize individually – Introduce each pup to new people, dogs, and environments on their own.
3. Start Early and Be Consistent
Start separation and training as early as possible (as soon as they settle into your home). Consistency is key to building their independence and confidence.
4. Consult a Professional Trainer
If you're unsure about how to manage two puppies, enlist the help of a certified trainer. They can guide you in implementing a healthy structure and identifying early signs of trouble.
Final Thoughts
Littermate syndrome is a serious but preventable condition. While raising two puppies at once may seem like a great idea, it often leads to unintended emotional and behavioral problems. With thoughtful planning, individualized care, and plenty of patience, it’s possible to raise well-adjusted siblings—but it takes significant effort.
When in doubt, one puppy at a time is the best path to a happy, balanced, and well-socialized canine companion.
Photos Courtesy of @Tinasyoungersiblings on Instagram, a littermate syndrome case I have been working with for since October of 2024, when they were 4-5 months old. Ricky (male, black and white) and Lucy (female, tan) were adopted from a rescue at together at 6 weeks old. There owners were never informed of the risk for littermate syndrome prior so when they started having anxiety, fear of people, and other issues they contacted me. Thank you to all of the fans of @tinahassomethingonhernose on Instagram, Facebook, and Tiktok for help bringing this syndrome and information on it to them.
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