What’s the only thing more exciting than bringing home a new puppy? Bringing home two new puppies. But as fun as the overload of cuteness may seem at the start, there can be drawbacks to adopting puppy siblings at the same time, including the risk of littermate syndrome – or the development of a sibling bond that is so strong, it can cause anxiety and aggression in dogs. 

Here, we examine the signs of littermate syndrome in dogs, how canine temperaments can create behavioural issues when adopting two puppies from the same litter and what dog owners can do to prevent anxiety and aggression in siblings.

What is littermate syndrome in dogs?

Littermate syndrome, also commonly referred to as littermate dependency, is a concept that describes a range of dependency behaviours when puppies from the same litter are raised in the same household. Strong bonds between littermates can contribute to a range of behavioural issues that can be problematic and upsetting for dogs and owners alike.

The ways in which these dogs are trained and socialised may also play a part in difficulties such as aggression and separation anxiety. Training pets and taking them out to socialise separately is essential to cultivating bonds between canines and the humans who care for them, and to ensure that their closeness to their sibling does not disrupt these relationships.

Littermate syndrome in dogs vs cats

Unlike littermate syndrome in cats, littermate syndrome in dogs is more widely recognised by animal behaviourists, and it’s also known as littermate dependency. This is due to the research into canine temperaments, or the biological differences in dogs’ behaviour that exist even between siblings.

Puppies are born with their own inherent temperaments and instincts that will develop as they grow older. These temperaments vary from shy to socially dominant, or alpha, and can cause unhealthy littermate dynamics. 

Problems that may crop up include a more nervous sibling experiencing separation anxiety when the alpha sibling is not with them. Signs of separation anxiety in puppies may include destructive behaviour. These issues can then be exacerbated later in life. If there are two alpha dogs in a household, struggles for dominance may break out as they age. This can be shocking for owners who have grown accustomed to their sibling pets getting along so well when they were younger.

Is it good to adopt two puppies from the same litter?

More often than not, adopting two furry friends from the same litter is not beneficial for pets or owners. While they may get on well for a period of time, once canine temperaments come into play, unexpected situations can unfold.

Another downside of buying two puppies from the same litter is that working one-on-one with each dog is simply more challenging. Since puppy training for two dogs at the same time can be burdensome, it is recommended to space out adoption by at least six months or until the first puppy is fully socialised and house-trained.

What are the signs of littermate syndrome in dogs? 

The first signs of littermate syndrome dog owners will notice is that the siblings are very attached to each other. This can happen as early as 8 to 10 weeks. The pets may not want to leave each other and appear anxious or agitated when they’re apart. These early signs of littermate syndrome can then develop into behaviours such as aggression, separation anxiety and issues with independent training. 

How to prevent littermate syndrome when adopting two dogs 

Dog owners wondering how to prevent littermate syndrome have a tough challenge ahead of them — one where a lot is down to them and the approach they choose to take. From separate training classes to walks, here are the best ways to avoid littermate syndrome and behavioural issues when adopting two dogs from the same litter:

Wait to adopt puppies until at least 8 weeks of age

Remaining with their litter until they reach the age of 8 to 10 weeks is instrumental in ensuring that dogs learn important capabilities such as impulse control and bite inhibition.

Bite inhibition is a dog’s awareness that they shouldn’t bite too hard when interacting with others. This is best learnt when a dog’s mother or littermates react instinctively with a yelp if a puppy’s bite inflicts pain. This teaches them that biting too aggressively and impulsively will have a negative effect. It may be harder for pets to learn these key lessons if they’re taken away from the litter at an inappropriately early stage. At 8 to 10 weeks old, puppies are also independent of the mother and can eat on their own as well as take in new environments.

Socialise puppies early and individually 

Once your puppy has been vaccinated, exposure to other dogs, humans of all ages and all kinds of environmental factors is crucial in facilitating their development. Having a littermate around can help them socialise safely away from outside pathogens.

However, only relying on a littermate for puppy socialisation may prevent them from bonding with other humans and getting comfortable and confident with their surroundings. 

The following tips on how each dog should be socialised — separately — can help set them up for success:

• Introduce your puppy to as many different types of people, places, noises, landscapes and even textures (like different floors) as soon as possible. 
• Make new experiences positive ones by giving treats and praise when they are exposed to the feeling of seeing or interacting with something unfamiliar. 
• Remain calm when introducing your puppy to new people and dogs — if you’re nervous, your pet will be nervous, too, and may become fearful of strangers in future.
• Start off slowly with new introductions — taking your puppy to a very busy public place can be overwhelming and may result in a fearful response to groups of strangers later on.

Separate littermates as much as possible at the start

To prevent behavioural concerns, puppies should do even the most basic activities, such as feeding, in different places or at different times. This helps avoid aggressive interactions between them as they fight over food or struggle to establish their own space.

Training should also be done separately, whether it’s inside or outside your home. Lead training should be done one-on-one initially. If the puppies attend obedience classes, they should do so separately, or if they must go together, two caregivers should work with them.

Can littermate syndrome be cured?

By the time an owner realises their dogs have suffered from littermate syndrome as a puppy, the dogs are likely already becoming embroiled in nasty fights. Strict training may be required for the rest of the dogs’ lives — and even then it may not address the situation.

If you suspect your dogs are showing signs of littermate syndrome, speak with a vet who can recommend the best course of action, which often will include a new training regime and routines at home to mitigate the fighting.

The bottom line on littermate syndrome in dogs

Littermate syndrome is when two puppies are adopted together and they bond too strongly with their littermate rather than the humans and other pets in the home. This can cause behavioural issues like dependency on one another, aggression towards others and separation anxiety. 

Treating dogs as individuals is the best way to harness their potential. To prevent littermate syndrome, experts advise that dog owners should start separate training classes, socialisation, playtime and walks as soon as they get the puppies home, and these should continue into the dog’s adulthood. Treating dogs as individuals is the best way to harness their potential.