WHY DO MOST ANIMALS HAVE TAILS?

by Whit Gibbons

February 5, 2017

Q: My 8-year-old daughter asked me if frogs and humans are the only animals that do not have tails. I had no idea, but it did make me want to ask my own question – how many different ways do animals use their tails?

A: Most vertebrate animals do indeed have obvious tails, whereas some major animal groups are unequivocally tailless creatures. Shellfish, snails and starfish come to mind. Many insects also have tails, although the anatomical origin is not an extension of the spine as in vertebrates. Nonetheless, insects use their tails for a variety of purposes, including stinging, spraying toxic chemicals at a predator and depositing eggs in the ground or into wood. Scorpions and stingrays are noted for actively using their tails as a weapon for protection. Some lizards use their tails in defense in a different manner. The tail breaks off when caught by a predator, allowing the rest of the lizard to escape.

The venomous Gila monsters of the Southwest have tails that are enormously fat but do not come off. They use the tail to store energy during periods when food is scarce. An African chameleon has what is called a prehensile tail that works like a fifth foot to hold onto limbs when climbing. Possums and some monkeys also have prehensile tails. A rattlesnake uses its tail as a warning device when it is scared. Many harmless snakes also vibrate their tails, and if they are lying amid dried leaves, they too make a rattling sound.

Baby copperheads and cottonmouths use their tails in an intriguing way. When they are born, and for a few months afterward, they have bright yellow tips on the ends. When the snake is coiled up, the tail points up from the center and serves as a lure to capture prey. Small lizards and frogs apparently think the tail looks like a worm ready to be eaten. In many dark-colored snakes, such as mud snakes and ring-necked snakes, the underside of the tail is brightly colored; when threatened, the snake displays the tail, which is in conspicuous contrast to the rest of the body. The sudden display of color can confuse a prospective predator. As the snake begins to crawl away, it lowers its tail. The predator is now searching for a bright color, and the snake’s dark body is well camouflaged against the dirt or mud, allowing it to escape.

The rubber boa of California has a short, blunt tail that looks almost identical to its head. When threatened by a predator, this snake arranges its body in such a manner that the tail is exposed while the head is hidden safely beneath the snake. The predator that bites the-tail-that-looks-like-a-head is in for an unpleasant surprise. The boa squirts a foul-smelling liquid from the tail region that would make any predator lose its appetite.

Alligators, crocodiles and fish use their flat-ended tails to propel themselves through water. Some sea snakes that spend almost their entire life in the water also have flattened tails that aid in swimming. Some crocodilians use their tails to knock prey off the bank and into the water. Family dogs I have had used their tails to knock coffee cups off tables. The tails of birds are aerodynamically essential for maneuvering in flight. Male turkeys and peacocks are noted for fanning their large, colorful tails during courtship displays.

Identifying how animals use their tails provides insight into some of the ecological purposes to which an appendage can be put. And the third grade is not too early to want to know why the creatures of the world are the way they are. A good class exercise would be to list the many ways animals use their tails. Enjoying ecology is often a matter of simple observations. Incidentally, frogs and humans do have tails during early development – in the embryo stage for people and during the tadpole stage for frogs.

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