(MS.Encarta) - Turtles were crawling and swimming around when gigantic dinosaurs walked Earth. The first turtles lived about 185 million years ago. The dinosaurs died out, but turtles lived on. Many kinds of turtles still thrive today.Tortoises are a kind of turtle that lives all its life on land. Other turtles live at least part of the time in water.
WHY DO TURTLES HAVE SHELLS?
A turtle is the only reptile with a shell. The shell is made of a bony or a leathery material. A shell is like a suit of armor. Most turtles can protect themselves by pulling their heads, necks, and legs into the shell.
The top part of the shell is called the carapace. This part covers a turtle’s back. The bottom part is called the plastron.
Most turtle shells are brown, black, or olive green. Some turtles have red, orange, yellow, or gray spots or lines on their shells. The painted turtle is very colorful. It has a yellow plastron and a black or olive carapace with red markings around its rim.
Tortoises have big, heavy shells to protect them from enemies on land. Sea turtles have light shells so they can swim more easily.
WHAT’S A TURTLE SHELL MADE OF?
Most turtles have shells that are covered with horny scales called scutes. The scutes are made from skin tissue. They overlap and make the shell hard and strong. Some turtles do not have scutes. Instead they have soft shells covered with tough skin.
The inner part of a turtle’s shell is made up of many bones. These bones include part of a turtle’s backbone and its ribs. The backbone and ribs are attached right to the shell. This is why a turtle cannot crawl out of its shell.
DIFFERENT KINDS OF TURTLES
There are about 270 species (kinds) of turtles alive today. Scientists group turtles by how they pull their heads into their shells.
Some turtles fold their necks sideways under the top of their shell. They are called side-necked turtles. Hidden-necked turtles bend their heads directly back into the shell. Sea turtles cannot pull their heads into their shells at all. But they are grouped with hidden-necked turtles.
Turtles come in all sizes. The largest turtle is the leatherback sea turtle. Its shell can be 8 feet (2.4 meters) long, and it can weigh over 2,000 pounds (900 kilograms). Other sea turtles, such as the green turtle and the loggerhead turtle, are also very large.
The largest land turtles are the giant tortoises that live on the Galápagos and Aldabra islands. They can measure 4 feet (1.2 meters) long and weigh as much as 600 pounds (270 kilograms).
Among the smallest turtles are the American mud turtles and musk turtles. Many mud and musk turtles have shells that are less than 5 inches (13 centimeters) long. The shell of the tiny speckled cape tortoise of South Africa is only 4 inches (10 centimeters) long.
A TURTLE’S BODY
The kind of limbs a turtle has depends on where it lives. Turtles that live on land have thick legs for walking. Turtles that live in water have long webbed toes for swimming. Sea turtles have flippers to paddle through the water.
All turtles have tails. Most turtles have short tails. American snapping turtles have long tails. The Asian big-headed turtle has a large, strong tail covered with scales.
Turtles, like other reptiles, breathe air through lungs. Even sea turtles must come to the surface to breathe. Some turtles can hold their breath for months at a time. They do this when they hibernate at the bottom of a pond or river during winter.
WHERE TURTLES LIVE
Turtles are cold-blooded animals. This means they cannot produce their own body heat. If it is cold outside, the turtle will be cold. If it is warm, the turtle will be warm. For this reason, turtles cannot live in very cold places, such as Antarctica. But they can live in most other places.
Side-necked turtles live in South America, Africa, and Australia. Hidden-necked turtles live in North America, Europe, and Asia. Turtles live in ponds and rivers. They live in forests and grasslands. Some turtles even live in deserts. Sea turtles live in the ocean.
WHAT TURTLES EAT
Some turtles only eat animals, such as insects, worms, and small fish. Some turtles only eat plants. Most turtles eat both animals and plants.
Turtles do not have teeth. They have a beak, similar to a bird’s, with ridges that they use to cut food. Turtles that eat animals have knife-sharp ridges for slicing through their prey. Plant-eating turtles have ridges with sawlike edges that help them cut through tough plants. Turtles have a tongue that helps them swallow food.
HOW TURTLES REPRODUCE
After mating, female turtles lay from 1 to 200 eggs on land. They dig a nest to keep the eggs safe. The baby turtles must take care of themselves as soon as they hatch from the eggs. Turtles that survive can live a long life. Some turtles can live more than 60 years. Some tortoises live to a very old age—up to 150 years!
THREATS TO TURTLES
Animals such as raccoons, snakes, and skunks love to eat turtle eggs and baby turtles. Many birds eat baby turtles as they crawl toward the sea. Fish eat baby turtles once they enter the water. Most turtles never live to grow up.
People are the biggest threat to turtles. People hunt turtles for their meat, eggs, and shells. They destroy places where turtles live by building farms and towns. They pollute the water where turtles swim. Sea turtles get trapped in fishing nets. Some species of turtles have become endangered. Many states and countries have passed laws to protect endangered turtles.
