tail bag

The tail of the horse and other equines consists of two parts, the dock and the skirt. The dock consists of the muscles and skin covering the coccygeal vertebrae. The term "skirt" refers to the long hairs that fall below the dock. On a horse, long, thick tail hairs begin to grow at the base of the tail, and grow along the top and sides of the dock. In donkeys and other members of Equus asinus, as well as some mules, the zebra and the wild Przewalski's horse, the dock has short hair at the top of the dock, with longer, coarser skirt hairs beginning to grow only toward the bottom of the dock. Hair does not grow at all on the underside of the dock.
The tail is used by the horse and other equidae to keep away biting insects, and the position and movement of the tail may provide clues to the animal's physical or emotional state. Tail carriage may also be a breed trait. Tails of horses are often groomed in a number of ways to make them more stylish for show or practical for work. However, some techniques for managing the tails of horses are also controversial and may constitute animal cruelty.

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