Turtles, Turtles, HAH HAH HAH

Turtles are the only reptile with a shell. Most turtles pull their head, legs, and tail into their shell, which serves as a suit of armor. Similar to other reptiles, turtles are cold-blooded. Their body temperature stays about the same as the temperature of the surrounding air or water. Some turtles live only on land, but others spend almost their entire life in the sea. Some turtles are known to have spent their entire life within a few kilometers of where they hatched. And of course we all are familiar with sea turtles who migrate thousands of kilometers from their birthplace.

There are about 250 different species of turtles, and they vary in size as well. The leatherback turtle is considered the largest, and grows from 1.2 to 2.4 meters long. In comparison, the common bog turtle is only about 10 centimeters in length.

Turtles are known for speed in the water, and we often associate their lumbering slowness on land with cartoon comedy. So it is surprising to note that the smooth softshell turtle, a freshwater species of North America, can outrun a human being on level ground.

A turtle's shell consists of two layers: inner and outer. The inner layer consists of bony plates and is actually part of the skeleton. For most turtles, the outer layer is made up of hard, horny structures called scutes, which are formed from skin tissue. However, soft-shelled turtles have an outer layer of tough skin rather than scutes. The top of the shell (covering the turtle's back) is called the carapace, and the part that covers the belly is called the plastron. The carapace and the plastron are joined along each side of the body by a bony structure called the bridge.

You can tell a lot about a turtle from its shell - turtles that live mostly on land often have a high, domed shell. Those that live more in water have a flatter, more streamlined shell. Some species of turtles, including Blanding's turtle, box turtles, and mud turtles, have a hinged plastron (remember – the bottom part). These turtles can close the plastron tightly against the carapace after withdrawing into their shell.

Their legs and feet are also a dead giveaway as to their habitat. Heavy, short, clublike legs and feet? That’s a land turtle – probably a tortoise. Most freshwater turtles have longer legs and webbed feet. Sea turtles have legs shaped like long paddles, with flippers instead of feet.

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