Is “LitterMate Syndrome” Real?

OR – is it time to change the conversation?

We talk about the recommendation that’s been around forever about not acquiring two puppies at the same time.  Is there good evidence for that?  And if not, what should we be talking about instead?


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  1. Socialization in Dogs and Cats:  The Scientific Basis vs. The Stories We’ve Been Told – 2 session webinar course, CEU approved
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  3. Socialization to Prevent Fighting Among Cats – Are Cats “Socially Incompetent”? – Article about socialization studies in cats
  4. Is Socialization Just for Puppies? – Confusion About Socialization and Behavior Modification


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  • Suzanne-Dan

    October 4, 2018

    We wouldn’t call whatever the issue is a “syndrome” either. It’s just an example of poor terminology that is too common in the dog training field. Although, we certainly aren’t the only field that suffers from fuzzy terms.

  • Cindy

    September 24, 2018

    This subject has come up on a dog rescue IG site. I had never heard about this previously. I googled “Littermaye Syndrome” and found your page. I am astonished this is even a thing. I have two littermates, who are the same sex – females. They get along just fine…sometimes with space; most of the time side by side or even snuggled together in the same dog bed. When was has had to stay at the vet, the dog at home is lost and super needy. My two girls are NOTHING alike in their personality or temperament. They have different likes and needs… just as two children or fraternal twins might. Both are very bonded to me, but in different ways. I have had no trouble training them. One is more alpha than the other. That doesn’t really have to do with them being siblings. There isn’t aggression or behavioral problems between them. I’m baffled by the concept of this being a “syndrome”. But this is just my own individual experience.

  • Suzanne-Dan

    March 16, 2017

    All really good points, Megan and what an interesting idea for gathering more data on this subject – to survey breeders. We had some input from others as well. We can see where raising littermates could create some tendencies toward certain problems, but I think our main point was that it wasn’t about “bonding” per se. We don’t know of any research into sibling aggression, but there is a paper I believe by Katherine Houpt and her colleagues that did find female-female aggression was more common than other gender pairs.
    thanks again for your input – you provided some great food for thought!

  • Megan Donovan

    March 16, 2017

    Hi Suzanne and Dan!

    While I agree that the issue may not be bonding, I would be interested in seeing more research into littermates being raised together. Anecdotally, in raising litters of puppies, I have seen a tendency toward aggression between same sex littermates in both my breeds, Border Collies and Rhodesian Ridgebacks. In the cases I’ve witnessed, the puppies have not been raised in the same household, but have seen each other regularly throughout adolescence at dog shows, family events, etc, and upon social maturity (or in one case earlier) these dogs have developed an intolerance for being around their littermate, despite remaining social toward other dogs. We also once kept two puppies until 16 weeks, and found that the very shy puppy completely blossomed once his very pushy, bold littermate had left the house.

    All this is to say that I do believe there can still be issues arising from raising littermates together, even if it isn’t related to over-bonding. The breeder/show community would be a good one to survey in this regard, because there are many instances where people raise puppies together, and any problems that arise are not likely from owner inexperience. I’d love to hear your thoughts, and if there is any literature on aggression/conflict between siblings.

  • Suzanne-Dan

    February 26, 2017

    We’ve had an interesting discussion about this in the Facebook group. There may well be some truth to the belief that two littermates have a tendency to pay more attention to each other than to their owners. However, as was brought up in the online discussion, it could be that folks who acquire littermates do so with the attitude that they can keep each other company and they won’t have to spend as much time playing and attending to them. THAT’s the factor that underlies the problems, NOT the “bonding” per se – which is more likely the result of how the owners handled the situation.

    Almudena – thanks for your compliment – you don’t know how hard I have to work to convince Dan to just relax and do this more spontanteously!! He’s getting better at it.

  • Jill Goldman

    February 26, 2017

    I agree with you. I believe people with two puppies (usually litter mates) would be more likely to treat them as one entity, instead of two individual dogs. As a result, the two dogs spend more time with each other than with the person (as in most cases due to a busy schedule, etc.). Any two puppies (litter mates or not) will bond with available social companions.

  • Almudena

    February 22, 2017

    Hey S&D!
    Boy, you guys are good on camera! Real naturals. Love the blue hair detail Suzanne!
    I must confess that I fell for this fallacy and now I know better.
    thank you for clarifying

  • Julie Cook

    February 22, 2017

    yep thats what I’ve always heard and or read don’t do it, anyway have friends who rescued two sisters JRT/Dachshunds pups. I’ve worked with the dogs privately on fear issues and was teaching a reactive dog class that both dogs enrolled in. The class was set up so each dog had its own private area (couldn’t see out) and these two dogs could not focus on anything we tried to do with them we had them at opposite ends of the room and tried side by side they only wanted to be together, they cried, pulled toward the other ones area when out (wish I had filmed it). ended up having to take this class and all other classes separately. Both dogs very fearful -a good reason not to get two at same time right?

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