By Suzanne Engelberg, PhD

Recently someone told me about a couple with two large dogs.  The dogs spent much of their day menacingly patrolling their property for invaders.  When the neighbor’s smaller dogs came into their own yard, the two large dogs raced to the fence line, baring their teeth and aggressively barking.  Understandably, the smaller dogs were intimidated. When the neighbor spoke up about this problematic behavior, the couple with the large dogs insisted everything was fine.  “Our dogs are just really happy to greet your dogs.  See, their tails are wagging.”

Suzanne & friend Gracie


This couple believes the myth that a wagging tail always means a happy dog.  The truth is that while tail wagging does often reflect pleasure, it can also express fear, hostility, submission, and other emotions.   A human parallel is smiling.  A smile often means happiness, but not always.  If a smiling human is fidgeting or looking away, their smile can reflect embarrassment, intimidation, or discomfort.  If their mouth is smiling but their eyes are not, the human could be pretending to be happy.  In other words, in order to know what a smile means, we have to look at the entire person as well as the situation. The same is true with dogs.  In order to understand what our dogs are trying to tell us with their tails, we need to look at the entire dog, as well the context.

There are three major components to a tail wag—height, speed, and direction.  In general, the higher the tail wag, the more aroused the dog is.  A dog with a tail wagging high may be feeling aggressive.  A dog wagging a neutral tail could be relaxed or happy.  A dog with a tail wagging close to the ground may be insecure or scared.   These are not hard and fast rules however, because whether or not a tail is considered high depends on how the dog normally carries its tail.  For example, chows naturally carry their tails high, and greyhounds naturally carry them low.  An aroused chow will carry its tail much higher than an aroused greyhound.

Suzanne with ODH foster ChiCha


Dogs also communicate through the speed of their tail wag.  For most dogs in most situations, the quicker the wag, the stronger the emotion.  A dog with a quickly moving tail held high may be about to attack.  A dog with a quickly moving tail at a neutral height is probably feeling very happy.  A dog with a slowly wagging tail held low could be giving a tentative greeting to an unfamiliar dog.

Within the last few years researchers have discovered that wags predominantly on the right side of the dog’s rear end (from the dog’s perspective) often reflect friendly comfortable emotions such as joy and enthusiasm, and wags mostly on the left indicate less comfortable emotions such as fear and aggression.  This means if we are facing a dog with a strong fast wag to the dog’s right (our left), the dog is probably happy to see us.  A dog with a slow, low wag to the dog’s left (our right) probably feels scared and intimidated by us.


Keep in mind that these generalities may or may not be true of your dog.  For example, my first ODH Final Refuge dog Bailey, a wonderful friendly Spitz mix, always wagged her tail low, even when she seemed happy.  Her vet explained that she had lost some of the muscle control in her tail, so she wasn’t able to raise it.  All Bailey’s tail wags were always low, regardless of what she was feeling.

Dogs with docked tails have a serious disadvantage in tail communication.  It’s very hard to see what their tail is doing while also paying attention to the rest of their body language. Without this major communication tool they can be easily misunderstood by other dogs and by humans.  Yet another reason why tail docking is a bad idea.

Suzanne and ODH foster Mali



In the situation with the large dogs whose humans thought the tails were expressing happiness, I don’t know for sure, but I suspect their tails were wagging fast and high, a frequent signal of strong aggressive feelings.  The aggressive barking and bared teeth are strong clues that the tails were not communicating happiness.  Other supporting clues are the dogs’ history of acting menacingly towards people and animals who came near their property, and the smaller dogs’ intimidation.  Looking at the context as well as the tail wags, it’s clear that the larger dogs were threatening to harm the smaller dogs if they got too close to the fence line.  (Fortunately the fence was strong, so the smaller dogs remained safe.)


The next time your dog wags her tail, see if you can tell what she’s trying to tell you.  Look at the height, speed, and direction of the tail, as well as the context.  You might be surprised at how much you understand!


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