Why Do Dogs Wag Their Tails?

Does a wagging tail mean a friendly dog?

“But…his tail was wagging! So I knew he was friendly—right!?” says the woman as she clutched her bitten hand.

What we have here is a failure to communicate. Well, the communication likely occurred, but no doubt there was a misunderstanding.

A tail is like a smile, and like smiles, they’re not all alike. Friendly smiles, phony smiles, shy smiles, evil smiles—we know the difference in human smiles. The thing is, there are just as many differences in tail wags! So know your wags!


dog tail wagging



Why Do Dogs Wag Their Tails?

While we humans often see a tail wag as a sign of happiness, dogs use their tails to communicate a variety of emotions. Dogs seldom wag their tail if no one is around to see it. Dogs without a tail are at a disadvantage in communicating, but if there’s a nub, there’s a way.

Other dogs are able to pick up on what the tail is saying. That wide slow wag, mostly to the right, probably is an invitation to be friends. But mostly to the left, or with a narrow arc or stiffly held—hold off for now. Dog’s heart rate will often rise when they see a dog wag to the left.

Why the difference in wagging right versus left? It has to do with brain lateralization, and the finding that at least in humans, the left brain (which controls the right side) is associated with pleasant feelings like security, attachment and  calm, while the right brain (which controls the left side) is associated with more negative feelings like fear and aggression. The tail tells the tale!


dog tails



Your Official Dog Tail Decoder:

  • The tail wag that most often precedes a dog bite is one known as the flag tail. It’s held high over the back, and often stiffly wagging in short arcs. You may see it in dogs barking at you through a fence, or in dogs greeting each other—right before a fight.
  • When the tail wags mostly to the dog’s left, he feels more negatively or cautious about what he’s looking at. His tail might do this when he’s faced with a strange or aggressive dog.
  • A superfast short-arc wag – almost like a quiver – is like one of those forced smiles—it means fight-or-flight, and you need to back off.
  • The higher the tail, the more confident the dog; the lower, the more worried. Since different breeds (and even different dogs) have various normal tail positions, look at the position relative to each dog’s norm.
  • A small wag with a narrow arc is like a shy smile – hopeful but unsure.
  • A big wag with a broad arc is like a good-ol’-boy wide smile – confident, happy, and ready to be buds.
  • When the tail wags mostly to the dog’s right, he feels good about what he’s looking at and wants to approach. Look for this when your dog greets you.
  • If the whole butt’s involved in the action—he’s just plain ecstatic!


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