Why Are My Littermate Puppies Fighting

Two puppies from the same litter might seem like a good idea. In reality, it can often cause a lot of behavioral issues down the road. Littermates are dogs who are raised in the same household past eight to ten weeks of age when puppies generally go to new homes separately. 

Littermate syndrome refers to behavioral problems exhibited by littermate puppies who were adopted together. Not every pair of twin puppies will develop this issue, but many do.

This is not a physical or medical diagnosis, but rather a host of anecdotal behavioral issues resulting from stunted social development. Here are some of the “symptoms” of littermate syndrome:

• Fear of unfamiliar people or dogs
• Intense discomfort in unfamiliar environments
• Anxiety when separated from littermate
• Aggression and fighting between the littermates

Why Do Twin Dogs Fight?

Littermates raised together from puppyhood to adulthood form an intense bond with each other that can often hinder their ability to learn how to respond to human and canine interaction. Puppies go through a key behavioral development period after around ten weeks of age, and a single puppy is generally more focused and receptive to human training than a pair of puppies.

This is of course not the case for every pair of littermates, seeing as there are many factors that influence behavioral development. Littermate syndrome could also be influenced by the decreased focus on a single puppy. Training two puppies simultaneously can be very challenging, requiring twice the work to ensure each puppy is well-socialized and well-mannered.

If Littermates are Bonded, Why Do They Fight?

There are a number of reasons why your bonded twin dogs are fighting. One theory is that two puppies living in the same household will have squabbles that are very difficult to manage.

Whereas solo puppies are introduced to new dogs in controlled, calm environments where you can use verbal commands and redirection to teach boundaries, two twin puppies will have lots of unsupervised playtimes. This can lead to fights that go too far when you aren’t able to get their attention and intervene.

Fights between puppies are often a result of overstimulation, which can quickly happen with two puppies living under the same roof. This behavior tends to be particularly true for littermates of the same sex.

Can Littermate Syndrome be Prevented?

If you already have two twin puppies at home, there are some steps you can take to prevent potential behavioral issues. Here are a few steps to follow if you’ve already brought home two puppies:

• Watch the behaviors of each dog closely to determine their individual traits. It’s helpful to understand each puppy’s limits as well as what motivates them (food, verbal praise, etc) to ensure you meet each puppy’s individual needs.
• Spend plenty of time with each puppy on their own to bond with them separately and to get them used to spend time apart.
• When they are old enough, introduce each puppy to plenty of different people and dogs in controlled, calm environments and use lots of positive reinforcement.
• Between 8-16 weeks of age, commit to socializing each puppy without their sibling present in many different environments.

How to Prevent Fights Between Twin Dogs

Twin puppies often fight more often or more intensely than two puppies from different litters. Here are some steps you can take if your twin puppies are fighting incessantly:

• If you see your puppies fighting, separate them completely into their respective crates. When possible, always supervise your puppies while they are interacting so that you can correct bad behavior consistently.
• Avoid physical forms of punishment like shock collars that will only lead to more fear and aggression down the road.
• Designate a “target” spot (a mat, rug, bed, etc) for each puppy that has an adequate distance between the two. Teach each puppy individually to go to their target spot. This way you can send them apart from each other verbally when they are misbehaving or fighting.
• After a fight, separate your puppies then reintroduce them in a neutral space. For instance, you and another person can take them on a walk where they are parallel to each other and controlled by the leash in case another fight breaks out.
• Ensure that each puppy is crate trained to give them their own individual spaces where they can decompress and not feel challenged for resources like treats or attention from their people.

While not all littermate puppies will develop behavioral issues, some do without the proper training. It is essential that you socialize each puppy diligently to avoid issues down the line. Common puppy training like teeth brushing and potty training is essential for both pups. Check out our puppy socialization tips for more details.

Once your puppies grow into adults, providing them more space to interact can help prevent common issues in multi-dog households like resource guarding and attention jealousy.

Installing a pet door is a great way to allow your dogs in and out of the house to expand their territory and give them plenty of space to burn off excess energy.