Littermate Syndrome: Everything You Need to Know

When you’re considering bringing a puppy home, the desire to adopt two at once is understandable. After all, the thought of separating brothers and sisters from the same litter can tug at your heartstrings. What’s more, you might think that training two puppies at the same time would be easier than adopting them one by one (and starting house training all over again!).

Unfortunately, the opposite is sometimes true: “Be prepared for two puppies to be twice the work of one,” says Dr. Heather Graddy, a relief veterinarian and veterinary behavior consultant in Englewood, Colorado. Why? Raising sibling puppies successfully can be a challenge because puppies from the same litter may develop a cluster of behavioral issues known as littermate syndrome.

If you have sibling pups that have been misbehaving (or you’re considering training two puppies from the same litter together), read on to learn everything you need to know about littermate syndrome in dogs.

Do Dogs Recognize Their Siblings?

If you’ve ever watched a litter of puppies at play, you’ve probably wondered: Do dogs know their siblings? From the beginning, pups recognize their littermates primarily by scent and that recognition is strongest when they are young, says Dr. Karyn Collier, medical director for wellness medicine at Saint Francis Veterinary Center of South Jersey.

Over time, though, a dog only retains the ability to recognize a sibling if they live together. After two years of living apart, siblings adopted by different pet parents are no longer able to recognize each other (1).

Like humans, littermates form a bond with each other from the start, which can strengthen or weaken over time. Sometimes this connection causes troubling behavioral issues known as littermate syndrome.

What is Littermate Syndrome?

“Littermate syndrome in dogs occurs when two puppies from the same litter living together develop such a strong attachment to each other that it interferes with their ability to interact in a normal manner with other people, other dogs, or any situation where they are not together,” says Collier.

This happens because littermates bond so intensely to each other that they fail to develop connections with their human family. This can make it harder for them to reach their full potential when it comes to good behavior, says Graddy. Puppies with littermate syndrome only interact with each other and become highly dependent on one another for a sense of safety and normalcy.

Littermate syndrome can affect dogs of any breed, and it may also affect unrelated puppies who are adopted at the same time and raised together.

The good news: not all puppy pairs develop littermate syndrome and pet parents can prevent significant issues with specialized training methods.

Signs of Littermate Syndrome in Dogs

At first, puppies with littermate syndrome may seem like they’re acting out or in need of obedience training. However, when dogs experience littermate syndrome, these behaviors are linked to their relationship to their littermate.

Signs of littermate syndrome in dogs can include excessive crying, whining, and destructive behavior when siblings are separated from one another, as well as a lack of interest in playing or interacting with other people or pets in your household, says Collier.

Here are a few signs of littermate syndrome in puppies and dogs to look out for:

Fear of unfamiliar people, things, places, or noises. Puppies may avoid interactions with new people, dogs, or things; become very still and quiet when you approach them; or bark, growl, and snap when presented with new things or situations.

High anxiety when separated from the other pup. Puppies may whine, bark, pace, pant, or exhibit destructive behavior when they’re separated from their littermate.

Unwillingness to eat alone. Dogs experiencing littermate syndrome may only want to eat if their sibling is present.

Unwillingness to engage with people or toys when alone. As previously mentioned, littermate syndrome sometimes causes puppies to focus on the other puppy rather than the humans in the home. Puppies who are only willing to play in pairs may be exhibiting signs.

Difficulty with basic training. Training two puppies from the same litter may take longer than expected because puppies are so distracted by one another.

If you’re considering adopting two puppies at the same time, it’s important to consider the challenges that may come along with this decision, so that you can devote the time and energy to positive-reinforcement training.

Challenges of Littermate Syndrome in Dogs

Littermate syndrome can be difficult for pet parents to deal with, due to the numerous behavioral issues that are involved. Pet parents may notice these problems early on, though they may not arise until pups reach adolescence, notes Graddy.

Most commonly, puppies develop separation anxiety due to hyper-attachment. Because puppies with littermate syndrome dominate each other’s attention, they may fail to learn how to communicate, play, and socialize with other dogs. Over time, this can result in fear and aggression when they’re exposed to other dogs.

Because dogs with littermate syndrome are so focused on each other, they may also bond less with their pet parents. In turn, they could fail to learn and develop appropriate social interactions with humans, too.

Littermate syndrome makes training two puppies from the same litter especially difficult, says Graddy. Because littermates are so focused on each other, it’s difficult for pet parents to get their attention. As a result, teaching puppies even basic skills becomes a greater challenge than it would be if you were training them one at a time.

In the worst-case scenario, littermates may attack each other. Aggression between housemates is more common between littermates adopted together than unrelated dogs adopted at different times, says Graddy.

For these reasons, adopting two puppies at a time may mean more work, not less, for some pet parents.

How to Help Behavior Problems

While raising sibling puppies successfully can be a tall order, it is possible. The key is to treat them as individuals, says Collier.

To help avoid littermate syndrome or put a stop to dogs showing early signs of attachment, there are a few things you can do.

Gradually separate your dogs. Use separate crates (slowly spaced farther apart until they’re no longer in sight), feed them in separate rooms, take them outside at different times, and sign them up for separate obedience training classes, says Graddy.

Socialize them each with other dogs. If socialization with other dogs is important to you, you may also want to take them out for separate play sessions with other pups. As your puppies adjust to their new normal, use treats and praise as rewards for staying calm when they’re apart, says Collier.

Allow puppy time together. Although you should maintain separate training, play sessions, and walks with your pups, you’ll also want to make some time for them to play together to help your dogs get along, says Graddy. Try a joint game of fetch or alternating tug-of-war games with you, she suggests.

“In order to help these pups develop appropriately, you have a lot of fun but time-consuming work in front of you for the next few months,” says Graddy. “While the amount of work will decrease after that time, it will be essential to continue separate training and play times with them throughout their first couple years and, in some cases, forever.”

If you find you don’t have the time, space, and energy to train and bond with your pups separately, consider reaching out to your veterinarian, a certified dog trainer, or a certified veterinary behaviorist for professional help.

How to Prevent Littermate Syndrome in Dogs

The easiest way to prevent littermate syndrome in puppies is to not adopt two pups at the same time, says Graddy.

However, preventing littermate syndrome can also be as simple as treating siblings as individuals from the moment they enter your home, says Collier. Make sure that your pups are getting plenty of exercise and interaction with you, your family, and others—not just alone time with each other, she says.

Another solution if you must have two puppies? Consider adopting unrelated puppies a few weeks or months apart, suggests Graddy.

And, if you’re a cat person, know this—littermate syndrome doesn’t seem to afflict kittens. In fact, many veterinarians recommend adopting kittens in pairs. They can be much easier to raise with a playmate and two is not much more work than one, says Graddy.