Dog behavior a ‘tail’ of two moods

By Sharna Johnson

CMI Columnist

After a few minutes of observation, it almost seemed futile. They just weren’t going to do it.

Nope, nothing but fanning tails that bobbed mostly to the right.

Sharna Johnson

Sharna Johnson

A short while later, no longer being watched, or so they thought, the dogs started squabbling over dinner, and what do you know, there it was.

The tail of the aggressor had switched directions and was absolutely wagging to the left.

Who knew — the wagging tail, long held to be the sign of a happy dog, is only half happy.

And it appears a dog can wag its tail and still be in a biting mood.

An Italian researcher said as much more than seven years ago after conducting a study in which he concluded the tail wag of a dog definitely has directional significance.

Assessing 30 pet dogs, Giorgio Vallortigara and his team documented the direction of the dogs’ tails when exposed to different things. When the dogs saw their owners, other humans and a cat, their tails wagged to their right side, but when they were faced with a larger, unknown dog, they wagged to the left.

Additionally, researchers found they also wagged to the left when they were alone.

Humans may not be able to tell one wag from another, but the next natural question for the team was whether or not other dogs could.
In a 2013 follow-up study, they showed dogs videos of other dogs wagging their tails. When the dogs saw other dogs wagging to the right, they remained relaxed and happy, but when they saw left tail wagging, they became immediately distressed with raised heart rates and increased anxious behavior.

The conclusion: Yep, they get it.

Admittedly, it has always been a mystery. Newly introduced dogs can greet each other with wagging tails and seem to be getting along fine one second, only to be locked in a ferocious death match the next, and all without a growl or obvious clue as to who or what started it.

Turns out, they’ve been silently throwing down the gauntlet all along.

Vallortigara’s theory is that the dynamic is tied to left-brain right-brain processes. Typically, the left side of the brain, which controls the right side of the body, is associated with the happier qualities and the right is associated with caution, which he believes, explains why a dog’s tail wags to the right when they are happy, and to the left when they are on the defensive or anxious.

A handy tool to have, watching the wag just might be the best key to understanding what is going on in a dog’s brain or at the very least, determining if they are happy to see you, or feeling edgy and possibly aggressive.

Of course only dogs really know what the wag means, and some tail wagging may be harder to judge than others, particularly with dogs that get the whole back end going or those who have no tail at all.

Whatever way the wag goes, when all is said and done, it’s not the tail that will deliver a slurpy kiss or a snappy bite, so don’t forget to keep an eye on the business end of the dog, too.

Sharna Johnson is a writer who is always searching for ponies. You can reach her at: