Animal tails serve diverse functions, helping animals keep their balance and convey information

A tail is the part extending backward from the end of the body in many animals, made up of the end of the spine along with the surrounding muscles, skin and hair. Tails differ enormously from one animal to another: some are slender like a whip, some are so short they are barely visible, and others are broad and flat like a paddle, with their shape often closely tied to the animal's living environment.

The functions of tails are highly varied. A cat uses its tail to keep its balance when walking along a narrow wall, fish and whales use their tails to provide forward thrust, and a monkey's long prehensile tail can wrap around branches to help it climb. Some geckos shed their tails to save themselves when in danger, dogs wag their tails to convey emotions, and foxes often use their bushy tails as a blanket to keep warm. Fat-tailed sheep in arid regions can even store fat in their tails, helping them get through seasons when forage is scarce.

In livestock farming, the tail is also an important part of the body for observing an animal's condition. Cattle and horses often use their tails to drive off mosquitoes and flies, and a pig's tail curling naturally usually means it is relaxed; if tail-biting behavior appears in a pig herd, it often signals problems such as overcrowding or unbalanced nutrition. Farmers can use the posture and intactness of the tail to detect abnormalities in their animals early.

Not all animals have tails: the tail vertebrae of apes and humans have degenerated, and frogs have no tail once they reach adulthood. The tail is closely connected to the spine and nerves, so when spending time with pets such as cats and dogs in daily life, do not pull their tails at will, to avoid causing injury.