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Little Dog Syndrome: Why Does My Small Dog Dislike Big Dogs?

As Trainers, a comment that we often hear from owners is that when out and about, their small dog may sometimes exhibit anti-social and/or aggressive behaviour when they encounter a larger breed.

“My dog thinks he’s 10 times his size”

“My dog just hates big dogs”

“My dog has little dog syndrome”

Does this sound like you?

Small breeds are not born with an innate aggression towards their larger counterparts and there isn’t a secret small breed society where they believe that big dogs are the enemy. Often, anti-social behaviour is a result of lack of early exposure. It can also be due to a negative experience having shaped the behaviour. Genetics can also play a significant part. The point is, there can be a multitude of reasons or contributing factors to their behaviour.


One reason that your small breed dog may react negatively towards large breeds is out of personal defence. Dogs are born with this natural instinct. Like all natural drives and instincts, the level of it varies between individuals. For survival reasons, small dogs often display higher personal defence.

Personal defence is similar to a person who has a clear personal boundary and doesn’t want that space invaded; in particular by strangers. Defensive behaviour can be evident from a young age. Defensiveness can often be made much worse by actually forcing a dog with this genetic trait to have social interactions with other dogs.

Instead of just allowing the defensive dog to approach others when it feels comfortable, forced socialisation can make a defensive dog ‘s behavior worse. Dogs communicate through body language and often give us clues that they don’t want to interact, however owners often miss these cues and insist upon their dog interacting. The dog will then often have to resort to a level of aggression to stop the interaction.

Examples are, your dog may show avoidance behavior. He/she may shy away from another dog, turn their head away or position himself/herself under an object like a chair. If others still encroach, the defensive dog may start to growl and bark, and if still not listened to can then potentially bite.

In Short: Respecting their personal space and boundaries is paramount to curbing any defensive behaviour in the future. When working on social interaction, have a defensive dog in a larger area (don’t make it feel hemmed in) and place the defensive dog with other dogs of suitable personality which in this instance would be with a calm dog.


Fear is another possible reason why a small breed may react untoward when they encounter a large dog on their outings. Fear will trigger a fight or flight response; if your small breed begins to show aggression it could very easily be a case of wanting to go into “flight” but because it is restrained on lead now has no option but to go into “fight”.

A small dog is not born being frightened of big dogs. Fear can be a result of a negative experience (a big dog splatting it with a paw) or lack of quality early exposure.

Our dogs go through a series of development stages in their young life. If you are not selective about the environments and encounters you allow your dog to explore, you can put your dog at risk of a negative experience. One negative experience in a development stage, may be all it takes to create a lasting bad memory. Even the most skilled trainer can’t erase memories.

Poor socialisation is also a contributing factor to “small dog syndrome”. A poorly matched playgroup can begin to shape anti-social behaviour. Therefore, it is crucial that you are selective about their playmates and ensure the match is appropriate. Quality socialisation is far more valuable than quantity.

It is important to safely introduce your small breed puppy to other dogs of all shapes and sizes but just be mindful of the temperament and energy of the other dogs, particularly if any are significantly larger in size. Building the small pup’s confidence around large dogs is important.

In short: Socialise your small breed but be selective of their friends. Don’t allow him/her to be knocked about by crazy large puppies or dogs.


Lack of early exposure is at the forefront of many behavioural issues that Trainers see today. Positive early exposure is of the highest importance to a puppy and will bridge the gap between the unknown and unfamiliar. Fear of the unknown and the unfamiliar is all too real in many cases and is not just reserved for our dogs.

For example, we aren’t afraid of cars because we have been around them since the day we came home from the hospital but if we missed this exposure and years later were to suddenly see one for the first time driving towards us at 60kms per hour, we’d probably have a heart attack.!

You see?

Because we can’t explain to our dogs “that big dog over there is not going to hurt you”, they need to be exposed early so that they have the confidence to draw that conclusion based on their own positive experiences.

The fact is, the world can be a big, scary place for a dog, especially for a small one. Because of this, it is of the upmost important to begin shaping confident behaviour the moment they come into your care.

A dogs social and environmental exposure time occurs within the first 16 weeks of its life. Often owners of small breeds are reticent for them to socialise at this age because of their small size but this is the time when they learn how to read the body language of others correctly and how to present themselves to other dogs correctly.

When exposing your small breed to a large breed, ensure that the small dog is on the ground rather than elevated in your arms. They need to learn to meet and greet correctly on the ground. Lifting a dog into the face of another so that they can meet is not socialisation and can be potentially dangerous.


Simply put, learned behaviour is something that has been rehearsed over and over again and reinforced by owners, in some cases to the point of no return.

Though it shouldn’t be the case, sometimes the rules that apply to our larger breeds don’t hold the same value or necessity for our small dogs. Because small dogs are physically easier to control, manage and seemingly do not pose any significant threat, essential training can be neglected and certain behaviours can become accepted and inadvertently encouraged.

Many owners of large breed dogs accept that training a dog is essential but often this doesn’t hold true with the smaller counterparts.

Though it may seem harmless for a small dog to aggress at a large breed (and often people will initially laugh when it occurs), it is important to note that this behaviour needs to be discouraged. The notion that a small or toy breeds will not physically harm another due to its size should not be an excuse to allow the behaviour.

Though a toy breed may not pose a threat to a big dog, unwanted barking could very well become learned if not immediately discouraged.

In addition to this, allowing a small breed to bark or aggress can in fact, be dangerous and life threatening. If a small dog is barking at every dog he sees, eventually that behaviour will be met with a reaction. If the dog is significantly larger or stronger, it can be especially dangerous.

ALL anti-social behaviour from ALL dogs should be discouraged the moment you see it.


Just like us, dogs will not get along with everyone. It is normal, and natural.

Whether defence, fear, lack of exposure or learned behaviour is the driving force of your small breed aggressing at larger dogs – the solution will not be a simple one. All the factors listed above are complex and will require troubleshooting.

A private consultation with your Trainer will be the sure-fire way to identify what lay at the core of the aggressive behaviour.

Once that has been established, then you can begin the process of rehabilitation but like anything, it will take time, consistency and patience.

No matter the size, allowing a dog to aggress at another is not okay.


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