Family Pets & Safety

Littermate Syndrome Is Being Blamed For A Recent Toddler Dog Attack, But What Is It?

When a 2-year-old in California was mauled by four puppies, headlines cited littermate syndrome. Canine experts say it’s complicated, but this is what parents should know.

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Little toddler girl squatting with litter of puppies while one puppy licks her toes

It’s a situation no family ever wants to find themselves in: a toddler, attacked and mauled by the family pets. And not by adult dogs, as one might assume — rather, 2-year-old Felicity Peden was mauled in June by her family’s four 12-week-old puppies in their California backyard. Thankfully, Felicity is expected to make a full recovery. But in the aftermath of the event, the Pedens have said they now hope their daughter’s terrifying incident will raise awareness around the dangers of littermate syndrome. Which begs the question: What is littermate syndrome?

The Pedens became aware of this purported behavioral condition in dogs when they signed the four puppies over to Animal Control, explains their GoFundMe page. In the time since, they have implored people to spread the word far and wide about the potential risk to families with multiple dogs. Understandably, it’s left the dog-loving community (and parents, in particular) shocked and concerned.

To help better understand littermate syndrome and how much of a threat it poses to families with dogs, Scary Mommy reached out to canine experts for more insight.

What is littermate syndrome?

“Well, while this term might help describe a group of behavioral issues that could be presented as a consequence of puppies raised together, not having proper training, and developing a hyper-bond, it is not necessarily a scientifically accepted term,” explains Paola Cuevas, a veterinarian, MVZ, and behaviorist with

Also known as sibling aggression or littermate aggression, littermate syndrome is said to present in puppies raised in the same household beyond the normal 8 to 10 weeks of age (at which point puppies are usually placed in homes).

Why does “littermate syndrome” happen?

It’s important to remember here that canine experts are hesitant to assign blame specifically to littermate syndrome without knowing the exact circumstances surrounding a situation.

“The term ‘littermate syndrome’ is too broad and encompasses such a range of behaviors that it isn’t helpful in understanding why dogs act in specific ways in specific situations. It’s a catch-all phrase that shouldn’t be generalized,” professional dog trainer Kevin Ryan of Superb Dog told us, adding the caveat, “While I don’t believe that littermate syndrome aggression is an actual thing, pack mentality most certainly is. Puppies will engage in pack behavior in the same way that adult dogs do. If one leader puppy exhibits a behavior, the other puppies will often adopt it as well and join in. If one puppy starts ripping apart a stuffed toy to get the stuffing out, other puppies will usually join in.”

Cuevas agrees, saying, “As in any group, puppies learn to feed on each other’s energy, whether fear, excitement, or aggression. This happens to gregarious creatures when we are in groups, especially at certain developmental stages. Visit any kindergarten or teenage year classroom, for example.”

In the case of puppies, if you keep two or more littermates (or any two puppies) together, they can become so focused on each other that they fail to socialize or be trained properly.

“Hyper-bonded puppies have most of their attention on each other and, in that scenario, any kind of training is challenging,” says Cuevas. “Without attention, there is no successful training. Moreover, puppies — just like kids — are learning, playing, competing, and establishing dominance. Two or more puppies growing together are wildly learning from each other instead of learning the rules of a domesticated life among humans or at least having the example or guidance of a mature co-specific.”

What breeds get littermate syndrome?

There isn't a specific breed that is more predisposed to littermate syndrome than others. It can be any breed of dog and can even happen in puppies that aren't related. If they were adopted and raised together, the same could happen.

What are some signs your puppies have hyper-bonded?

Uh oh. No one warned you about this possibility, and now you’re raising two (or more) adorable pups at the same time. Here are a few signs your pups have hyper-bonded and are in danger of developing behavioral issues:

  • Separation anxiety: The pups will have a close, dependent bond.
  • Aggressive “play” or fighting: They could also grow to be competitive with each other.
  • Fear of strangers: This may include other dogs or even their own human family.
  • Failure to potty train: Difficulty in this department may affect one or more pups and is indicative of a general failure to follow commands.

So, even something typically as simple as housetraining a puppy that is hyper-bonded becomes problematic. “There will be dominance and submission between [the puppies], and each has its behavior challenges. They will learn aggression and resource guarding to get what they need. Some will become fearful and lack the confidence needed to behave among humans or even interact with other dogs outside of their group,” explains Cuevas.

Does littermate syndrome pose a threat to kids?

“I’ve been training puppies for over 30 years, and I’ve never encountered ‘littermate syndrome’ as a cause of aggression towards people. There are simply too many factors involved in such incidents to identify a direct correlation,” says Ryan.

“That being said, I strongly advise dog owners against raising littermates together in one home. There are a host of problems that often occur in these situations (though I’ve never witnessed aggression towards humans as one of them),” he adds. “Simply put, it is very difficult to properly socialize littermates that are raised together. They are always dependent on each other much more than dogs from different litters, and always have this bond from the womb to fall back on.”

What can you do to minimize tragic puppy-child interactions?

Both Cuevas and Ryan emphasize that the best way to prevent a tragic situation between puppies and children is to keep a close eye on their interactions. The following are their top suggestions for child safety around family dogs.

1. Train, train, train.

Step one? A commitment to training. “Puppies need a lot of attention — individual attention — to learn the rules of the ‘living among humans’ game. They need to learn boundaries instead of competition and learn emotional control instead of fear and aggression responses,” says Cuevas, noting that kids and puppies can form great bonds but must learn to safely interact with each other. “Both need to learn how to respect each other’s space and boundaries ... It is easier to train a single puppy at a time. Since most parents have a busy life and are not dog behaviorists, this is a wise decision.”

2. Don’t leave kids alone with canines.

“You should never allow your small children to play with dogs unsupervised. Never. While puppies may appear harmless because of their youth and size, they can pose a threat to children,” says Ryan. “Puppies only play with their teeth (just watch a litter of puppies playing with each other) and, at that age, their puppy teeth are like sharp needles. This is when they are learning bite inhibition — how hard they can bite on skin — and you don’t want your child to be their learning tool.”

And when you’re unable to supervise, separate your dog from the kids. If you can’t give them your full attention, place the dog outside or in their pen or instruct your little one to play in their room with the door closed. It’s important to give them separate activities to keep them busy, but how you divide them depends on your child's age and how much training your pup has gotten. So the older your kid, the less assertive the separation has to be.

3. Keep kids upright.

“Even when supervised, small children shouldn’t be down on the floor playing with puppies. They should stand tall so as not to invite play, which involves nipping and mouthing from the pups. When small children get nipped by a puppy, they will usually squeal in response, which often only excites the puppy even more, encouraging more of that same behavior,” explains Ryan.

4. Make sure tiny hands aren’t holding food or toys.

As Ryan puts it, “Food is a master motivator for dogs.” So, when they’re locked in on acquiring that treat, any training or manners they may have can fly right out the window. “The same goes for toys that the dog may perceive as a toy for them as well. Many a child has been bitten by a dog who has watched a child unknowingly taunt them with a ball.”

5. Don’t feel obligated to give your puppy “siblings.”

While neither Cuevas nor Ryan feels as though littermate syndrome is a scientifically proven cause of aggression, they still agree that it’s generally smart not to raise littermates together. “One puppy is usually more than enough at one time,” says Ryan. “When clients tell me that they want to get two littermates so the puppies can ‘keep each other company,’ my response is, ‘We need pets. Pets don’t need pets. They are perfectly happy just to be your pet.’”

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