It may seem like a horse’s tail just hangs back there swatting flies, or, when you least expect it, you.  But that tail serves many other purposes vital to a horse’s well being.

Its tail aids in temperature regulation, acts to safeguard delicate reproductive tissue, and assists in balance.  It is a vital communication center, signaling to other horses and to humans what a horse is thinking and what it intends to do.

A horse’s tail is part of his spinal column.  It is made up of approximately 18 vertebrae—the exact number depends on the breed.  The bones are largest closest to the hips and get smaller towards the end.  The last one is pointed.

Two arteries pump blood to the tail, but since it is so narrow, circulation isn’t as good as in the rest of the horse’s body.  That’s why injuries to the tail take a long time to heal and infections seem to linger forever

Where the tail attaches to the buttocks, the skin is 5/8 inches thick, which is as much as ½ inch thicker than most of the rest of its hide.  The hair on the tail is also thicker and coarser than the rest of the body hair.  Most horse tails are straight, but a few breeds, such as Morgans, have cascading waves.  Horses that evolved in cold weather, like Icelandics, have thick, heavy tails. The thin silky strands in an Arabian’s tail developed as a result of its life in the desert.

Horses communicate through body language, and they use their tails to send many kinds of messages to other members of the herd.  Standing head to tail, friendly horses swish flies from each other’s faces.  At play, horses often hold their tails high, a sure sign of excitement and high spirits.  An irritated horse will signal displeasure with a twitch of his tail, clearly indicating that a swift kick may be next.  The offender, duly warned, clamps his tail between his hind legs, showing submissiveness.

Some tail signals are concerned entirely with reproduction.  In the presence of stallions, mares in heat lift their tails up and to one side to indicate sexual receptiveness.  When a mare is not “in the mood,” she’ll twitch her tail side-to-side in a hostile manner, telling the stallion to “back off.”

In just such ways, horses use their tails to signal to their owners about their mood, health, and physical state.  A horse that swishes his tail from side to side in an agitated manner is saying that he’s not happy with what he’s being asked to do or what is happening to him.  A tightly clamped tail, accompanied by a humped rump, is a sure sign the horse is ready to explode. 

Dull brittle tail hairs may signal a dietary deficiency or perhaps disease.

It is normal for a certain amount of a horse’s tail hair to fall out as it is replaced by new hair.  Humans have been recycling this hair for generations.  It is used to make various kinds of brushes, and woven into stiff fabric, called haircloth, to be used in the construction of furniture.  Strands are braided into bracelets, hat bands and watch bands.  Violin bows are made from the hair of horses from China, Mongolia, Argentina, Russia and Canada. Some violinists swear that white horse tail hair is best because it is less coarse, resulting in a smoother sound.

Whether swatting flies, communicating to the world, or providing useful material for humans, a horse’s tail is doing a lot more than simply hanging.