The nightmare of Littermate Syndrome
As a behaviourist dedicated to specialist support for the dogs that need it most, there are extremely few cases that I cannot or will not work with. I believe very strongly that almost every dog can be helped to succeed - from severe and chronic fear to high levels of aggression. But at the beginning of 2023, I made the decision to no longer work with littermates. The short reason is that the issues are unresolvable as long as the siblings stay together. Let’s talk about why.
What exactly is littermate syndrome?
Littermate syndrome refers to the range of psychological and behavioural issues that littermates develop as a direct result of being raised together through adolescence or into adulthood. This means that the behavioural issues that the dogs develop are present exclusively as a result of being raised with another sibling, and not due to each individual dogs temperament, genetics, or other factors that go into their development. The symptoms of littermate syndrome are driven by an intense codependancy and typical present as some or all of the following:
Intense or chronic over excitement at a young age, inability to settle or relax (less than 6 months).
Intense or chronic separation anxiety relating to the other sibling at a young age (less then 6 months).
Chronic whining, howling or barking.
Chronic pulling and driving on a lead when walked together, even when using a head halter.
Intense, unlimited ‘play’ at a young age, escalating to high levels of aggression and fights between the siblings as they reach adolescence. Fights resulting in serious injury or death (usually but not exclusively 8-18 months).
Intense resource guarding of food, toys, furniture or owners resulting in fighting, as above.
One sibling develops a chronic lack of confidence, presenting as nervous anxious of fearful behaviour. (6 months onwards).
High levels of territorial or possessive aggression and reactivity towards strange dogs and/or people, almost always by the more nervous sibling. (6 months onwards). Inability to practice social behaviour outside of the family unit.
Whilst every pair of siblings is different, the common theme in every case is the severity of the issues - particularly when assessed comparitive to the age of the dogs and the environment they are raised in. One of the hardest things about owning littermates is the ‘waterfall’ descent as the dogs reach adolescence. It is incredibly common that owners can lull themselves into a false sense of confidence that they are beating Mother Nature, and succeeding where others have failed, only for the small issues to escalate very rapidly - often with very severe consequences.
Is littermate syndrome Inevitable?
It would be disingenuous to say that siblings have to develop littermate syndrome, in the same way that it would be dishonest to say that you are guaranteed to get cancer when smoking cigarettes. The natural world doesn’t work well on the basis of statistical probabilities or binary measurements. However, the likelihood that an ordinary dog owner would be able to successfully raise two siblings is incredibly slim, and the conditions for success are generally unachievable in most home environments. And to be really blunt about it, if you’re reading this article or looking for help with a behavioural issue between siblings, it’s already too late. I know that may be a brutal reality, but it needs to be said, because once things take a downturn, aggression escalates quickly and the health and safety of both dogs is at risk. Knowing this, and with the high likelihood that both dogs will succeed individually in separate homes, it is always better to draw the line sooner rather than later with littermates.
The Incredibly High bar for success
So what are the requirements for two littermates to succeed? Anecdotal evidence from dog owners we’ve never met on social media seems to suggest it can be done, even though many experienced professionals advise against it. Aside from the high likelihood that these ‘success stories’ ignore or downplay issues as ‘normal dog behaviour’ - what is required for two siblings to be raised together successfully?
Male/Female pairs typically have more success than same sex pairings.
Pairings where one of the siblings is naturally more confident or ‘dominant’ and where one of the siblings is naturally more calm, easygoing and submissive tend to result in less competition.
Siblings raised in a home with a number of additional, psychologically balanced adult dogs (excluding the mother of the puppies) to act as teachers and diffuse the intensity of the bond between siblings.
Both siblings need to sleep separately, eat separately, train separately, socialise and exercise separately - at least for the first 8 months of their development.
Let’s be absolutely clear about that last point. Both siblings need to in essence live two separate lives under one roof until they are at least late adolescents.
Low Prey Drive, low Defence Drive breeds (almost exclusively found in the Gundog group, including labradors and retrievers) tend to have higher success rates.
The obvious question from a professional point of view is as follows - if all of the above environmental and selection requirements are met, is it reasonable to assume that a family has the capability and commitment to raise two puppies independently under the same roof? In my experience, I have never yet had a client that was capable of doing so.
The Reasons why people try (and fail) to resolve Littermate Syndrome
When working with clients who have littermates, there are similar reasons which I see repeatedly as to why people would try and resolve the issues. The most common sentiments I have heard for keeping two puppies are:
“We owe it to the dogs to make it work. We bought both of them, and its our responsibility to fix the mistakes we’ve made”.
No, you don’t. You owe it to the dogs that the both have the highest chance of success - which will always be separately rather than together. Keeping the siblings together is either a case of ignorance if you dont know better, or wilfully putting both dogs in a dangerous situation where they are far more likely to fail (be more nervous, more aggressive or reactive). These are also not your mistakes to fix. You are fighting against inevitability in the natural world - and you likely weren’t aware when you took the dogs on.
“Dog X belongs to me, and dog Y belongs to my partner. Neither of us wants to give up our dog”.
In the human world this may be true, but in the natural world its irrelevant to what is right for each of the dogs as individuals. When it comes to deciding which of the pair to keep and which to be re-homed, the decision should be made on the basis of which of the dogs is most compatible with your existing lifestyle, and which will adjust most easily to moving into a new family environment. Some people choose to keep the more confident, less problematic dog - but it is often easier for the more confident of the two dogs to move on to a new family, and for the more nervous of the two to stay with you whilst you receive professional support to help them adjust and build confidence.
“The issues aren’t that bad. They’re just a little boisterous and we can handle the reactivity.”
The issues aren’t that bad, yet. These behaviours escalate very rapidly. Sometimes aggression to the other sibling can happen as early as 6-8 months, but more often reaches a peak around 18 months when both dogs are in the height of adolescence. The overwhelming majority of owns push through the first 18 months before reaching a crisis point, and then having to firefight until they can find a home for one of the dogs - which is incredibly stressful and only delays the inevitable.
“I saw Trainer X, Y & Z online / a friend of a friend had littermates that were fine.”
If you are reading this article, the chances are that your individual situation is not. Professional trainers generally have the environment, experience and other beneficial factors around them to make it much easier for them to succeed. You are not a professional trainer, and you don’t have any of the advantages they have. Don’t make the mistake of thinking that its a simple case of probability, love and care. It isn’t.
What should we do with our Littermates?
The unavoidable reality is that at some point, one of the pair will need to be re-homed. The overwhelming number of people wait until the situation is dangerous or unbearable, or until they are burned out and can no longer handle the issues, before finally being ‘pushed’ into finding a new home for one of the dogs. This is the unfortunate reality of human nature - and I expect that most people with littermates reading this article will choose to ride out the storm in the hope that their dogs are fine, or choose to manage the issues.
My advice is to make an honest assessment of the behaviour, and compare your dogs behaviour to what ‘normal’ should look like. Assess excitement, energy levels, ability to relax. Behaviour around other dogs. Competiton, dependancy. Look objectively at what you have, with the knowledge of how littermate syndrome may impact your dogs behaviour. If you see the red flags, plan in advance to find a home for one of the pair - so that you have the time to choose the right place, and to adjust to the reality that their life with you is just one chapter in their overall story.
Our Readers respond - living with littermates:
April from Utah writes:
“Thank you for your article on littermate syndrome. Please please please keep telling people the hard truths about this issue. We obtained our girls from a rescue organization, and at 18 months, yes, littermate syndrome popped up. I'm certain it was probably brewing beforehand, but we did not know what to look for. Looking back, we cannot identify where it went wrong, but it did. We trained them separately, crate trained in their own crates in different rooms, fed them separately. We simply did that because we wanted to avoid them depending upon each other overly much. It seemed like common sense. It wasn't anything we were aware of. We did let them play together, however. We'd certainly never heard of littermate syndrome. We do still have both girls, but here are the caveats: we do not have children, we are older adults, we've had many dogs (including 2 chows) in the past, and most importantly, we have a house that can be (and is) divided. We have 2 separate doors into our backyard. We switch the girls back and forth every other day. Neither "owns" any space in the house or yard. They basically switch back and forth between my husband and myself each day, so they're not being left all alone all day either (we work from home). We take great pains to make sure they never meet. We went through many trainers over a five year period who said they could help us. Ultimately, no one really could. I did contact the rescue after the issues became serious and expressed my dismay that not only did they adopt 2 littermates into the same family, they never told us it could be an issue. They then acknowledged they *KNEW* it could happen. The last behavioral therapist we consulted stated the odds with 2 females from the same litter having littermate syndrome is upwards of 60%. The rescue failed us. Thank you for bringing attention to littermate syndrome. I can't even imagine if we'd had children or grandchildren that may have been hurt by our dogs, just for being around them at the wrong time. Friends who have planned on getting littermates think we are nuts when we tell them not to do it, and think we must have done something terrible to the girls when they were puppies, or that we had horrible trainers.... I've heard it all. This situation only works for us because on a daily basis, they live in 2 separate spaces. Most people would not have the resources or patience to do that. I can't say thank you enough for trying to make people aware. I really hate seeing people make the same mistake we did, especially when they have children in their home. The fights between the dogs are vicious, as you know. During the first one I thought they might seriously injure or kill each other. One dog lost a tooth against her sister’s skull. Thankfully that was the worst of it.
Individually, each girl is very sweet and laid back. They both love people. Together though? No. Also, because of their negative experiences with each other, neither can be around other dogs. They were socialized in training classes from the day we brought them home (they were 8 weeks). All that socialization went out the window when the fights started. I can’t blame them; if I’d had such bad experiences, I’d feel the same. That in a nutshell is why we didn’t rehome one of them. People tend to disregard what they haven’t experienced, and we felt the chances of a new family deciding to add another dog to the mix was too high. We could not in good conscience pass along a potential problem. We love them, so it’s worth it to us.”
