Dogs are amazingly social animals that have evolved a pattern of behaviors that are meant to communicate their feelings and emotions to the living things around them. While humans rely mostly on vocalizations and the tone, cadence and volume of their speech to communicate their mood, dogs use several parts of their body. Of course dogs do use vocalizations and most owners can easily tell the excited bark of a dog at play from the menacing bark of a dog protecting his or her property.
In addition to their bark, dogs use the motion of their tail, what we call “wagging” as a way to communicate their state of mind. It is interesting to note that even dog breeds that have little or no tail naturally such as some of the terriers as well as the Corgi’s and cattle dogs will still wag their tail, even though they don’t have nearly as much to wag. In areas where docking the tail is still permitted, even dog’s with docked tails still continue to wag their tail, even though there really isn’t much there.
Nature has helped many breeds of dogs and other wild canine species to highlight the movement of their tail by providing lots of profuse, fringe or hair in breeds such as the Irish Setter or with heavily plumed tails such as the Spitz breeds. In addition the tail coloration tends to lighten closer to the tip, often even becoming pure white. This adds a visual distinction to the movement of the tail and makes signaling enjoyment, excitement and happiness much easier for these breeds. In wild populations such as wolves and coyotes the tip of the tail may also be very dark or even pure black, again a color differentiation that will draw attention.
Dogs only wag their tails at living things they are happy to see. The faster the tail moves back and forth the more excited the dog is. A gentle or lazy waving of the tail is a content signal, while a rapidly moving tail is a true sign of eagerness and excitement. It is interesting to note that dogs don’t wag their tails towards inanimate objects, which clearly indicates that the dog understands that the tail wagging is a form of communication. In dog terms the wagging tail is identical to a happy expression or a smile on a human face.