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What Is Littermate Syndrome? (And why you should never get two puppies!)

Updated: Oct 10, 2023

Getting two puppies sounds like the dream for people who want a multi-dog household, I know. Twice the amount of cute puppy cuddles, keeping two siblings together and raising them together, so they can play and be friends? I entirely get the appeal, but it’s not a good ideas for a few reasons, most importantly: The risk of littermate syndrome.

So what is Littermate Syndrome? Littermate Syndrome is an term that refers to a lot of the behavioural problems that you see specifically in small puppies that have been raised together. An important thing to note is that, despite the term, the puppies in question don’t actually have to be littermates to develop these behavioural problems. Raising two puppies from different litters together can still result in littermate syndrome.

At the lowest level, what you often see is behavioural problems from a result of co-dependency. The littermates develop such a strong bond with each other that it interferes with their ability to interact normally with other dogs, other people and they don’t develop the strongest bond with their owners, which has a knock-on effect with all their training.

If you’ve ever met littermates that have been raised together, you’ve probably noticed that there’s always a “shy” one and a “confident” one. The shy puppy becomes incredibly introverted and follows around the confident one almost constantly and does not do well when separated or when tasked with making their own decisions alone. Incidentally, the confident one also becomes anxious and distressed when separated, far more so than is normal. Their faux confidence is tied to their littermate and doesn’t exist to them as an individual dog. It’s a shame for both of the dogs who could’ve led happy, assured lives if raised in regular circumstances.

And then, of course, we have the highest level, where we get aggression.

They’re already having behavioural problems, as a result of the lack of proper social interactions and the unnatural environment they’ve been raised in. Neither of them are strong and confident dogs, likely you’re beginning to see behaviours like separation anxiety and reactivity emerge and gradually the reactivity snowballs into full-blown aggression. Lots of littermates end up having to be separated after they hit maturity because they begin fighting with each other. The ones that don’t fight each other often can become aggressive and reactive to the other dogs or people that they didn’t properly interact with.

Dogs are not pack animals. We know this. Raising them like this is unnatural and, ultimately, not that surprising when it causes problems.

A responsible breeder will never sell anyone littermates and will not sell you a puppy if they know you already have one or plan to get a second. Anyone breeding dogs and bringing them into the world should know about the risks of Littermate Syndrome and there’s no excuse for them not to know- it’s a huge red flag if they don’t and you should run a mile if a breeder ever offers you two puppies because there will undoubtedly be other issues with their breeding.

If you want a multi-dog household- I get it, I do too- the absolute best thing you can do is get a brilliantly bred puppy, (temperament is everything) raise it for 12-18 months and when you’re happy with where they’re at, then add your second. Puppies are hard work – they need almost constant attention and monitoring and they come with a huge training to-do list, and honestly, they deserve your undivided attention. It's also worth remembering that twice the puppy comes with twice the costs. You're going to have two lots of vet bills, two times the food and insurance costs. Two times the pet care if you need to go away or require a dog walker. Trust me when I say that you do not need two at once.

Finding the right puppy and breeder can be hard work so click here for our Good Breeder Checklist!

Happy Training!



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