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Littermate Syndrome- What it is, who it applies to and is it even real?

Corgi with Yorkshire cross

What is it?

Littermate syndrome refers to the behavioural issues that may arise from raising two puppies together. These behavioural issues can occur with sibling puppies or two puppies from different litters but similar ages.

While some owners successfully raise sibling puppies without complications, the risk of co-dependency and behavioural issues remains. This article explores the common symptoms of littermate syndrome and provides practical tips for preventing and addressing these potential challenges.

Behavioural issues that may arise can be either minor or significant. There is no ‘one size fits all’ approach to raising a puppy (let alone two). Each puppy is an individual and requires a unique training approach. Each puppy needs one on one time by themselves and with their owners as well with their littermate.

Littermate syndrome can manifest in various ways. Recognising these symptoms early is crucial for effective intervention. Common signs include:

· Extreme co-dependency

· Separation anxiety when separated

· Poor social skills

· Fear of strange dog/people

· Difficulty training

· Aggression towards each other

In most littermate pairs, one puppy starts to become more confident than the other. The anxious puppy will thrive from more training and confidence building exercises away from the more confident pup. This training is necessary if the puppy is expected to maintain a healthy state of mind when their sibling is out of sight.

Addressing potential separation anxiety and co-dependency.

Due to each puppy needing to learn how to cope without their sibling, puppies need to be separated at times. This process must start slowly, especially if the puppies are currently spending every second together.

The best way is crate training the pups and slowly moving the crates further and further away every other day.

A tie up exercise, starting with the puppies out of reach and then gradually further away, can also work if you are not using crates.

Once the puppies are calm while apart in the same room, you can move to separate rooms and out of sight from each other.

Offering a high-value food based enrichment toy can change the time away from their sibling from a negative experience into a positive one. This can be items such as a filled Kong, appropriate size raw bone, frozen Lickimat or a cow hoof.

Training as individuals.

Next I would like you to also consider that each dog has its own unique training needs and that it is more effective to train each dog separately. This could be 5 minute each, 2-3 times a day. This time can be spent working on luring them into different positions such as sit, lie down, stay or heelwork to begin the foundations of training. Training each puppy as an individual allows you to go at their pace while also strengthening your bond and trust with them.

As the puppies start preforming commands as cued, we can start training together. Remember to take training back a few steps due to the added distraction of their sibling. Make it simple and increase the difficulty as each puppy adapts to working along side their best friend.


Do not allow puppies to be pushy or bully each other. They must respect each other’s space, boundaries, and items.

If I am patting Puppy A, Puppy B is not allowed to charge its way in. If Puppy B wants a pat, they must wait their turn.

Puppy B is not allowed to steal treats or toys from Puppy A. They can play with toys together, however, look out for signs resource guarding like when Puppy B steals the toy from Puppy A and guards the toy from them. They are not allowed to be stealing dinner from each other either, this is another reason why we feed separately.

When playing, make sure that one puppy is not being over dominant by holding the other on the ground for long periods of time and not giving them a chance to get up.

When puppies are interacting, keep an eye out for tension building or Puppy A showing clear signs that they do not want to play while Puppy B ignores them.

This can include body language such as:

· Head turning/looking away (Disengaging with the situation)

· Lip licks

· Ears tight against the head

· Tucked tail

· Tense body

· White of the eyes showing (whale eye)

· Slight lifting of the lip to show teeth.

If one of the puppies are showing these signs, please remove the other puppy from the situation.

Sometimes dogs play amazingly, other times tension builds, and fights can break out. It can be a great idea to train a “Break” command. This can be an effective way to stop puppies from playing before it starts to escalate. Ensure you don’t use this command too often and reward the puppies when they do “Break” therefore stopping having fun by play is still valuable to them. You can start this by saying “Break” before using a loud clap to startle the puppies out of low energy play. When they stop playing, mark with ‘good’ reward with a treat.

Another way is saying “Break” then trying to redirection each puppy with a treat in each hand.

Maintaining independence

Ideally as puppies, they are fed them separately, taken for separate walks, played with separately, and even sometimes taken to the vet/groomer appointments one at a time.

Yes, this sounds like a lot of work and unfortunately, it can be, however, these steps are crucial to decrease the risk of littermate syndrome from happening to your pups.

Red and white border collie. Tri-coloured border collie


While littermate syndrome can be challenging to rectify once ingrained, proactive measures during puppyhood can prevent its development. Recognising each puppy as an individual, with unique needs and preferences, is key to fostering a healthy relationship with both dogs. By investing time and effort in early training and separation, owners can ensure their puppies grow into well-balanced, independent individuals. As the puppies get older, time together can be increased. Regardless, even as adult dogs with no littermate issues, I still recommend taking them out for separate walks and training for time to time. Each dog has different likes, dislikes, and personalities and even siblings deserve to be viewed as individuals.


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