Today there are only seven species of sea turtles alive. Sea turtles are considered to be living relics because their ancestors lived in the Age of the Reptiles, more than 90 million years ago.
A sea turtle spends nearly all its life at sea. Only females come ashore and then only once every several years to lay eggs on the beach. A female digs a pit in the sand, lays her eggs, and then covers them. When the eggs hatch, the tiny sea turtles instantly craw out and head for the sea. This is probably the most dangerous time in their lives. Many of them never reach the sea. They are eaten by birds, mammals, or crabs on the beach; if they reach the shallow water along the coast, they may be eaten by meat-eating fishes. The lucky ones that make it out to sea often find protection among floating sargassum seaweed.
Unlike fishes, which breathe with gills, sea turtles have lungs and breathe air. Sea turtles can hold their breath for several hours, so they don't have to stay at the surface of the ocean.
It takes a long time for sea turtles to grow up. Some may live longer than 30 years. The largest of the sea turtles, the leatherback, grows to more than 6 feet in shell length and weighs more than 1,000 lbs. Fully grown sea turtles are well protected by their armor of shell and bones and have very few natural enemies. The greatest predator of adult sea turtles is man.
When humans first started exploring the oceans, there were millions upon millions of sea turtles. Explorers depended upon sea turtles for food during their long ocean voyages. They were especially fond of the green sea turtle. Since then, hunters have killed so many sea turtles and have taken so many of their eggs from beaches, that sea turtles are now endangered. In addition to the construction of homes and buildings near nesting sites, man's use of nesting beaches for recreation, and the accidental drowning of sea turtles in shrimp nets have all contributed to the decline in populations.
Most nations of the world now have laws protecting sea turtles and their nesting areas, and sea turtles are very slowly beginning to increase in number. But the Atlantic ridley turtle is so rare that it may still become extinct.
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