Sea Turtles are members of the superfamily Chelonioidea and inhabit all of the world's oceans except for the Polar Regions. Sea turtles are marine reptiles and one of earth's most ancient animals. Sea turtle species separated from other turtle species more than 100 million years ago. The major differentiating factor between the two families is that sea turtles are incapable of retracting their head and legs into their shells as other turtles do. Sea turtles spend the majority of their lives in the ocean. They were once plentiful but all are now listed as Critically Endangered excepting the Flatback Sea Turtle which is listed as Endangered. There is insufficient data on the Flatback to determine its true status. The Flatback, which feeds on sea cucumbers, jellyfish and seaweed, has the most limited range of all sea turtles, and resides solely along the northern coast of Australia.
There are seven species of sea turtle. It was once thought there were eight, but DNA testing has determined the Green Sea Turtle and the Black Sea Turtle are the same species. Among sea turtles, the Leatherback is the odd turtle out. It does not possess a hard shell, but instead has a carapace made up of thousands of small boney plates that lie under a tough, leathery skin. Also, the Leatherback's carapace does not possess the geometric scutes of other turtles. Instead it has seven ridges running lengthwise from head to tail. A Leatherback's spine is not fused to its carapace either, and it is able to tolerate cold water, increasing the range of its habitat. The Leatherback is the largest sea turtle, reaching lengths of 10 feet and weights of 2,000 pounds. They are open ocean dwellers and can dive to depths of 3,000 feet in search of their favorite food, jellyfish. It is rare to see a Leatherback near shore unless it is arriving to lay eggs.
All sea turtles nest on coastal beaches. Some species, like the Kemp's and Olive Ridley will nest on only one particular beach in the entire world. These turtles take part in simultaneous mass nesting migrations called "arribadas," or arrivals. These arribadas now help conservationists keep track of population. The Kemp's Ridley is the smallest (2 ft long, 100 lbs.) and most endangered sea turtle. They are carnivorous and feed primarily on crabs, clams, urchins and shrimp. The Kemp's Ridley likes warm, shallow coastal waters and adults stay primarily in the Gulf of Mexico. They are the only sea turtle to nest during daylight. The Olive Ridley is a little larger than the Kemp's and enjoys a larger population. They remain on the critically endangered list because of the few nesting sites available. Olive Ridley Turtles can be found in coastal waters of the Pacific, Atlantic and Indian Oceans.
The Loggerhead is perhaps the most recognizable sea turtle in the United States. It is common to see Loggerhead nests roped off on beaches from Virginia to Florida, and down into the Caribbean. Loggerheads spend most of their time close to shore in estuaries and sheltered bays, but they will migrate 1,000s of miles and cross oceans to reach warmer waters or better nesting sites. The Green Sea Turtle is the only herbivore of the sea turtle species. Juveniles will eat some worms and crustaceans but, as adults, they feed strictly on sea grass and seaweed. Green's are the second largest sea turtle and can be found in all temperate and tropical waters. The Hawksbill Sea Turtle prefers coastal reefs, lagoons and rocky sea beds where it can find the sponges it feeds on. Hawksbills were hunted extensively by humans for the beauty of their carapace. The deep mottled colors of its shell were highly prized for jewelry, eyeglass frames, combs and brushes. Thanks to conservation efforts and strict laws prohibiting hunting, there is now a growing nesting population of Hawksbills on the coast of Yucatan, Mexico.
All female sea turtles lay more than one "clutch," or group of eggs, each nesting season. The female comes ashore, digs a deep hole with her rear flippers and then lays her eggs in the soft sand. Most clutches contain 60 – 200 eggs, depending on species. When the female is finished, she will carefully cover the eggs and use her front flippers to "knead" the sand and obscure any trace of the nest. The temperature of the sands will determine the sex of the hatchlings—the warmer the sand, the more females will be born. After an incubation period of 45 – 70 days (dependent on temperature and turtle species) the young will emerge. They will not leave the protective cover of the sand until night, when they will dash for the sea. Sea turtles can live to be over 80 years old.
Fun Sea Turtle Facts
- Many beachside residents in the United States are required, by law, to douse their lights during nesting season. Scientists believe that hatchlings need to follow reflected moonlight and starlight to find the sea. If human light pollution dims nature's beacon, the hatchlings become disoriented and won't reach the safety of the ocean.
- In 1991, an estimated 610,000 Olive Ridley turtles nested in a single week on a beach in India.
- Sea turtle populations are difficult to count because juveniles and adult males do not come ashore.
- Sea turtles (like other turtles) have no teeth, but the jaw of each species is specifically designed for its food source.
- Sea turtles hear vibration more than sound as we know it. Their eyesight underwater is good, and they have an excellent sense of smell.
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