The Size of A Dog's Tail Messes up Dog Language!

The Size Of A Dogs  Tail Messes Up Dog Language

By --Con Slobodchikoff

We all know that dog tails communicate information to other dogs and to people: happiness, friendliness, playfulness, fear, aggression, and status.

But what happens when the tail is artificially shortened (docked)? Are other dogs affected by this tail shortening? In the United States at least, more than one third of all dog breeds have traditionally had their tails docked. What does this is do to dog body language?

This is been a difficult question to answer scientifically because experiments have been so hard to perform. If you're using live dogs with short and long tails to study this question, you have a lot of factors other than tail length that could confuse the issue. You have all kinds of body scents, ear positions, general body posture, and behavioural interactions that can modify the response of other dogs to short or long tails.

A recent behavioural tool has been to use robots to study the behaviour of other animals. With a robot you can test for specific things, such as a short tail versus a long tail on a dog, and everything else stays constant: the robot is still the same size, stays in the same position, doesn't have any confusing smells, and doesn't engage in any behaviours that could modify the response of an approaching animal.

Using a robot, a study has recently looked at the effect of short and long tails on the approach behaviour of other dogs (Leaver, S.D.A. and T.E. Reimchen. 2008. Behavioural responses of Canis familiaris to different tail lengths of a remotely-controlled life-sized dog replica. Behaviour 145:377-390).

The experimenters did this study in a place where there are a lot of off-leash dogs in Victoria, British Columbia, Canada. They used a robot about the size of a Labrador retriever, and attached to the robot either a short tail (9 cm or 3.5 in) or a long tail (30 cm or 12 in). Using a servo mechanism, they could make the tail either wag or stand still. They videotaped the approaches of 492 off-leash dogs and assessed the conditions under which the dogs either freely approached the robot or hesitated in their approach.

They divided the approaching dogs into two categories: smaller dogs (those whose shoulder was below the shoulder of the robot) and larger dogs (those whose shoulder was above the shoulder of the robot).

They found that the dogs differed in their approach to a short tail versus a long tail.

Both larger and smaller dogs tended to approach the robot without hesitation when the robot had a long, wagging tail, and tended to hesitate more when the long tail was motionless. We might expect this because a wagging tail generally signals friendliness while a motionless tail can signal potential aggression.

On the other hand, both larger and smaller dogs seemed to have a difficult time determining whether the short tail was wagging or still. Both the larger and smaller dogs tended to approach either the wagging short tail or the still short tail at about the same rate, a rate that was below the rate of approach for a long wagging tail and above the rate of approach for a motionless long tail.

It was as if the dogs couldn't see the difference between a wagging short tail or a motionless one and had to make a guess as to whether to approach or not.

So it seems that tail docking does introduce some confusion into dog language, making it more difficult for dogs to determine whether a dog with a short tail is friendly or potentially aggressive.

Fortunately for dogs, the practice of tail docking seems to be decreasing in frequency, allowing more dogs with normal-sized tails to be able to accurately communicate their intentions to other dogs.