Why Do ... Dogs Wag Their Tails? 

by Kevin Behan

The quick answer is that a dog wags its tail for a reason which seems self-evident enough, that being it's the tell-tale mark of a friendly dog. Indeed, anyone who's stood too near the pounding tail of a prototypical friendly breed such as a Labrador retriever, can take a veritable shellacking from the wack of its wiggle. But if friendliness were an altogether accurate interpretation, why is it that so many people are bitten by a dog that's wagging its tail, often very enthusiastically? For this and other reasons, the science of behaviourism has called into question the popular wisdom that dogs wag their tails out of friendliness. The definition that the science of behaviourism prefers is that a dog is wagging its tail as a submissive overture to a superior member of its pack. For example, if one observes an inferior wolf approaching a superior one, tail-wagging is a pronounced feature of his body language.

But this isn't a wholly satisfying either because when adult wolves regurgitate food to their cubs, the cubs' tails are wagging and so are the adults. Are the adults being submissive to the cubs and the cubs to the adults all at the same time? That seems like a confusing scrambling of signals and it's my experience that the nature of behaviour is never that ambiguous. The recurring theme of this newsletter will be to make the point that submission and dominance while expedient, convenient, and seemingly reasonable means of making sense of canine behavior, can¹t really accomodate the data. For if a dog is showing submission to a human out of respect, why then would he bite such a person? Such paradoxes plainly call into question the traditional scientific interpretation.

A thinker on dogs who I respect quite a bit, although I will hope to show ultimately that he doesn¹t go far enough in placing his observations into the proper context, is Desmond Morris. We will be referring to his work often in these pages and for our current purposes I call on his book "Dogwatching" wherein he writes at length on the phenomenon of tail-wagging. He states: "The only emotional condition that all tail-waggers share is a state of conflict. This is true of almost all back-and-forth movements in animal communication. When an animal is in conflict it feels pulled in two different directions at the same time. It wants to advance and retreat simultaneously. Since each urge cancels the other out, the animal stays where it is, but in a state of conflict. Essentially the animal wants to stay and wants to go away. The urge to go away is simple--it is caused by fear. The urge to stay is more complex."

Attraction in conflict with fear, this is why dogs wag their tails and it's an interpretation that perhaps is quite surprising to many. It also needs further elaboration, for example, if we consider a dog who we can be sure isn't ever going to bite anyone but who nonetheless is wagging his tail, what possible fear might there be for this dog in a situation where it's only about to be petted, or fed, or any other number of pleasurable experiences?

The full answer to that question will be covered in an upcoming article entitled, "The Nature Of Fear". Desmond Morris' assertion that the the urge to go away from fear is simple, is mistaken. Fear is a little more complex than he has presumed. But putting that dynamic aside for the moment, for now I would simply like to elaborate on Desmond Morris' insight by going a step deeper into the phenomenon of the friendly dog wagging his tail.

Tail wagging is indeed a state of conflict. But the conflict is arising from the following condition, it is the state of the body vibrating with more energy than the body at that moment is able to conduct given whatever action is currently available to it. In other words, there is more energy trying to go through the pipe, the dog's body, then the pipe can accommodate. Wagging the tail is the body's physiological response for dissipating the excess energy. It would feel better to the dog if the body could process the energy in a straightforward active range of behaviors, for example making hearty physical contact, but for a number of reasons which we'll discuss when we consider the nature of fear, it can't.
Hence the state of conflict.