Turtles are an ancient group of reptiles that developed when the dinosaurs were still alive. There are about 250 species, or types, of living turtles. The turtle is known as a slow-moving animal, and indeed certain land turtles are quite slow. Oddly, sea turtles tend to move faster, even on land. Turtles that live on land are often called tortoises. Some edible turtles are known as terrapins in the United States. Where turtles liveTurtles are found in most parts of the world, except in the coldest regions. They are abundant in southeastern North America and southeastern Asia. Most turtles live in freshwater. Other species live in salt water or on land. Turtles are found in seas, lakes, ponds, salt marshes, rivers, forests, and even deserts. Physical characteristicsTurtles have changed little in appearance since their origin some 200 million years ago. Size and weight vary greatly among different species. The smallest, such as mud and musk turtles, may be less than 4 inches (10 centimeters) long and weigh less than 1 pound (0.5 kilogram). On the other hand, the Atlantic leatherback turtle grows to a length of more than 6 1/2 feet (2 meters) and may weigh more than 1,500 pounds (680 kilograms). A hard shell surrounds the turtle's body, protecting its vital organs like a suit of armor. The shell is separated into an arched upper section and a flat lower section. The upper section is called the carapace. It is joined to the turtle's ribs and backbone. The lower section, called the plastron, is fused with the turtle's breastbone. In many species, the turtle can tuck in its head, legs, and tail. The turtle completely retreats into its shell for protection. Most turtles draw the neck backward into the shell. However, in side-necked turtles, the long neck folds sideways in order to fit into the shell. The shell of the snapping turtle does not fully cover its belly. The snapping turtle protects itself by biting its enemies with its powerful jaws. In some turtles, the shell is quite strong. A box turtle's shell, for example, can support a weight 200 times greater than the turtle. Turtles are toothless. They tear apart food with their beaks. In some species, the jaws have sharp, jagged edges. Turtles have sturdy legs with short feet. The toes have claws. Sea turtles have paddlelike flippers for front feet. Turtles have a keen sense of sight, smell, and taste, but they cannot hear very well. All turtles breathe with lungs. Some species can also breathe through certain tissues of the throat, skin, and the anal region while in the water. This enables them to stay underwater for hours, or even days. FeedingTurtles eat living or dead plant and animal matter. The animal food may include worms, snails, slugs, insects, jellyfish, clams, mussels, crayfishes, and other crustaceans. Many tortoises eat only plants. Turtles can survive without food for long periods of time. However, when food is readily available, they eat frequently and can grow very fat. Some turtles can store water in a specialized bladder, which helps them to survive long droughts. Reproduction and growthTurtles usually breed once a year. However, turtles are highly unusual in that the female can lay fertile eggs for years after a single mating. All turtles lay their eggs on land. The female lays the whitish eggs in a hole that it digs with its hind legs. It may lay from one egg to more than 200 eggs at one time, depending on the species. After covering the opening of the nest, the female turtle leaves immediately. It neither cares for the eggs nor nurtures the young. As a result, birds and small mammals often prey upon the eggs or later the freshly hatched turtles. The turtles may hatch in less than 45 days or more than 100 days, depending on the kind of turtle and the temperature in the nest. In most species, the temperature in the nest determines the sex of the new turtles. Warmer temperatures generally produce females, while cooler temperatures produce males. Turtles reach maturity in about three to eight years. In some species, the females grow twice as large as the males. Turtles generally live longer than most other animals. Several kinds have lived longer than 50 years in captivity. Some species may live more than 100 years in the wild. Turtles and humansSome turtles are kept as pets, but the sale of small ones is illegal in the United States. Pet turtles, especially small ones that might be touched by very young children, can transmit a bacterial infection. In many regions of the world, people eat turtle meat and eggs. In the United States, certain species of turtles are harvested for sale to restaurants. As a result, many native species, such as the snapping turtles, have been greatly reduced in numbers. In addition, turtle populations have decreased worldwide as their environments have changed or been destroyed. Many turtle species, including most tortoises and sea turtles, are in danger of completely dying out. |