Elephants use their tails to swat biting insects. (Eureka/ALAMY)

When I get home at the end of the day, I am greeted by 35 pounds of bouncing fur and three tails wagging a mile a minute. After lots of rubs and kisses, my three Havanese dogs settle down for a game of fetch and a few naps before bedtime.

Of course, life with dogs is not without its ups and downs. If I catch one of my pups doing something wrong, a stern look from me will send those furry tails between their hind legs faster than you can say “Scooby Doo.”

Before we had kids, my wife and I had cats. Although feline tails are designed more to help cats balance than to show their feelings, whenever we opened a can of Friskies, two cats came prancing into the kitchen with their tails raised so high, they looked like exclamation points! (On the other end of the emotional spectrum, housecats will swish their tails from side to side if a pesky human is bothering them.)

When a housecat rubs against your body, he is marking you with scent glands on his face and the base of his tail. While this may seem affectionate, you are actually being identified as part of the cat’s territory. We can’t smell this scent, but he can.

But what about wild members of the animal kingdom? What purposes do their tails serve?

Birds steer themselves with their tails. (Denis Farrell/Associated Press)

Monkeys and other primates have two types of tails: non-prehensile and prehensile. Like cats’, non-prehensile tails are designed to help an animal with balance as it swings, climbs and jumps through its environment. A prehensile tail, on the other hand, can also grab objects and has the ability to act like an extra arm as well as a tail. Some non-primates, including opossums and lizards, have prehensile tails that help them climb and safely walk along tree branches.

Rattlesnakes have evolved a special organ at the end of their tails that enable them to warn intruders and keep enemies at bay. The rattle is made from keratin, which is the same substance found in fingernails, animal hooves and horns.

Birds use their tail feathers for steering. Fish and sea mammals use their tail fins for steering and to propel them through the water. (Fish tails move side to side; the tails of sea mammals move up and down.)

Grazing animals such as elephants, zebras and giraffes have long, thin tails with a tuft of hair on the end. These tails function like built-in fly swatters that enable the animals to protect themselves from biting insects.

Alligators store fat in their tails, and foxes use their bushy tails like a blanket to keep them warm in the winter.

A dominant male hippopotamus uses his tail like a propeller to spread his feces (poop) around so other males don’t try to horn in on his territory.

Bonus fact: Humans don’t have tails, but we have a small bone at the bottom of our spine called the coccyx (cok-siks). The coccyx, which is commonly referred to as the tailbone, helps support your body when you’re sitting.

Howard J. Bennett

Bennett is a Washington pediatrician. You can read past KidsPost articles and other cool stuff at his Web site, www.howardjbennett.com.