Dogs uses their tail as rudders when they swim, balance, and run, helping them turn corners and negotiate jumps. A swish helps keep insects away. Dogs in cold climates curl their tails around their bodies for warmth, often burying their noses in the furry tips to take the chill off the air they breathe. Of course, waving, wagging, or lowering the tail can mean cheerfulness, unease, or fear.
A dog’s tail speaks volumes about his mental state, his social position, and his intentions. How the tail came to be a communication device is an interesting story. The dog’s tail was originally designed to assist the dog in its balance. When a dog is running and has to turn quickly, it throws the front part of its body in the direction it wants to go. Its back then bends, but its forward velocity is such that the hindquarters will tend to continue in the original direction. Left unchecked, this movement might result in the dog’s rear swinging widely, which could greatly slow its rate of movement or even cause the dog to topple over as it tries to make a high-speed turn. The dog’s tail helps to prevent this. Throwing the tail in the same direction that the body is turning serves as a sort of counterweight, which reduces the tendency to spin off course. Dogs will also use their tails when walking along narrow surfaces. By deliberately swinging the tail to one side or the other in the direction opposite to any tilt in the body, the dog helps maintain its balance, much the same way a circus tightrope walker uses a balance bar. Quite obviously, then, the tail has important uses associated with specific movements. However, the tail is not particularly important on flat surfaces, when a dog is simply standing around or walking at normal speeds. At these times, it becomes available for other uses. Evolution again seized an opportunity and now adapted the tail for communication purposes. The tail is also an extension of the spine, so never tug a dog by its tail. This causes a jolt to the entire spinal column.
