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A tail is a distinct, flexible appendage attached to the torso of the rear section of an animal’s body. It is the body part that corresponds roughly to the coccyx in mammals, reptiles, and birds. Tails are primarily a feature of vertebrates, although some invertebrates, including scorpions and springtails, have tails. Even snails and slugs have tail-like appendages sometimes referred to as tails.

Animal tails have numerous functions. For fish and other marine life forms they provide a locomotive force and function as a rudder to enable them to smoothly glide through their watery world. A whale’s tail is called a fluke, which moves up and down instead of side to side as fish tails do (Fielding, 2011, p 24). The fluke propels the bus-sized whale rapidly through the water. Without it, the whale could not swim. Snakes are actually a very long tail with a head.

The tails of grazing animals, such as horses, zebras, lions, giraffes, cows, and elephants, are indispensable to sweep away insects that bother them. Called fly-swatter tails, they are usually long and thin with a thick fur tuft at the end similar to a fly swatter (Fielding, 2011, p. 7).

Tails are also used to effectively communicate an animal’s physical and emotional state. The best example of a talking tail is that of dogs, most of which communicate quite well by wagging their tails to convey their friendship, mood, feelings, wants, and disappointments. All canids, including domestic dogs, indicate emotions both by positioning and by movement of their tails. Dog lovers claim they can tell a dog’s mood just by studying the tail.

Tails are also used for social signaling. Some deer species flash the white underside of their tails to warn others of possible danger. Some species’ tails are armored, others, such as scorpion tails, contain venom.

Some animals, including kangaroos, use their tails as a third leg to sit on while competing for mates, to munch on leaves on tall branches, and to help them balance while carrying their joey’s (babies). Others, such as New World monkeys and opossums, have prehensile tails that allow them to swing from one tree branch to another, hanging only by their hand like tail that can firmly grip tree branches. They also can anchor to a small tree branch while they sleep on a larger tree branch (Fielding, 2011, p. 10).

Many other primates have tails, including lemurs, which they can use as an extra hand to hold on to their mother––or to branches, to help them balance while transversing the arboreal world, or even to help them obtain food (Fielding, 2010, p. 11).

The tails of some animals are used to keep the herd from separating as they travel. Elephants will hold on to each other’s tails when they travel long distances to help insure the herd stays together (Fielding, 2011, p. 7). The young on many animals such as elephants hold their mother’s tail when they feel stressed or threatened.

Some lizard species can detach their tails from their bodies (called “casting”) to escape predators. Once detached, their predators are either distracted by the wriggling detached tail, or are left with only the tail while the lizard flees to safety. Tails cast in this manner usually soon grow back, though the replacement tail is typically darker in color than the original.

The tails of most birds end in long feathers called rectrices that are used as a rudder to help the bird maneuver when in flight. Without these long, specially designed tail feathers, they would be unable to fly. Their tails also function as brakes by moving them forward, then spreading them out to act as a windbreaker. The extra-stiff tail feathers of other birds, including woodpeckers and woodcreepers, allow them to brace themselves firmly against tree trunks to enable them to peck wood. Their tails also help the bird to balance while perched. In some species—such as birds of paradise, lyrebirds and, most notably, peafowl—modified tail feathers play a role in courtship displays.

Some animals, such as squirrels and skunks, have large ostentatious bushy tails that they can curl around themselves in cold weather to help stay warm and keep dry (Fielding, 2011, p. 15). Some animals, such as squirrels and cats, clean and groom their tail by running their front teeth through the fur, similar to how humans use a comb or brush to prep their hair.

Some animal lovers have nominated the chameleon as having the most beautiful tails in the animal kingdom. They can tightly coil up their very colorful jewel like tails, and then, like a whip, spring them open to threaten any provokers that happen to wander by.

Human embryos have a misnamed tail that is about one-sixth of the size of the embryo itself. As the embryo develops into a fetus, the growing body catches up with the tail. This tail-like structure was long claimed to be a vestigial structure, but we know that it has an important function. The long tail-like structure exists because the nervous system, including the brain and spinal chord, develop first to help coordinate the development of other body systems.

Children are occasionally born with a “soft tail,” that lacks vertebrae, but has blood vessels, muscles, and nerves. Although a few documented cases of “tails” exist containing cartilage, or even up to five vertebrae, these examples are all developmental abnormalities and are normally excised by a surgeon.

The claim that humans lost their tails, although commonly made, does not make sense in view of the fact that the relevant structure exists only as a platform for the development of an essential part of the body. The beauty of the situation is that we do not need a tail to help us balance or function as a third arm, or communicate. We have been provided with better features to allow us to do all the tasks that tails do so well for many animals.



Albright, Eric. 2005. “Human Fetuses have Tails, Proving that Evolution is True. 7/5/2005. http://fredericksburg.com/News/FLS/2005/072005/07052005/109580

D’Aulaire, Emily and Per Ola D’Aulaire. “The Wonderful Anti-Ant Machine.” International Wildlife, 9(6):24-30, November-December.

Dagg, Anne Innis. 1979. “Behind Almost Every Animal is a Good Tail.” International Wildlife, 9(6):18-23, November-December.

Fielding, Beth. 2011. Animal Tails. Waynesville, NC: EarlyLight Books.

Herman, T. E. and M J Siegel. 2008. “Human Tail–Caudal Appendage: Tethered Cord.”

Journal of Perinatology, 28:518–519.

Zappler, Lisbeth (author) and Jean Zallinger (illustrator). 1972. The Natural History of the Tail. Garden City, NY: Doubleday.

Jerry Bergman
December 2013

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