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Saturday, 7 August 2010

The Largest Turtles On Earth

The leatherback turtles are renowned as the largest turtles on earth and one of the largest living reptiles (they can reach up to 2 meters in length and 900 kg in weight). Leatherbacks are easily distinguished by their carapace (shell), a leathery type of skin (somewhat flexible and almost rubbery to the touch) which covers its shell in place of the hard, bony shells which cover all other sea-going turtles.

Although turtles spend most of their lives in the open sea, the females come ashore during the breeding season to lay their eggs. The female drags herself ashore on a sandy beach, and when well above the level of the highest tide, she excavates a hole in the sand with her flippers and lays about 80 eggs in it. Then she covers the eggs with a large amount of sand and finally returns to the sea.

Incubation lasts about 7 to 10 weeks in the warm sand. The temperature inside the nest determines the sex of the hatchlings. A blend of male and female hatchlings occurs when the nest temperature is something like 85.1 degrees Fahrenheit (29.5 degrees Celsius), whereas higher temperatures produce females and cooler temperatures produce males. When the young turtles hatch, they scratch their way to the surface and head accurately for the sea. On their way to the sea, they run a gauntlet of terror, for sea birds, crabs and lizards gather over and on the beach, attracted by this sudden supply of fresh meat. Only a fraction of the newly hatched turtles ever reaches the sea.

Numerous leatherbacks meet an early end due to human activity. It is estimated that only one in 1000 turtles make it to adulthood and breeding age. Many leatherbacks are caught in fishing lines/nets, or are hit by boats. Leatherbacks can die if they swallow floating plastic remains which can easily be mistaken for their favorite food such as jellyfish. Some of these poor creatures have been found to have approximately 5 kilograms of plastic in their stomachs.

Leatherbacks are presently designated as endangered under the U.S. Endangered Species Act. The amount of leatherbacks in the Atlantic seems to be stable or increasing, but regrettably the Pacific population is declining at a disturbing rate as a result of egg harvest, fishery by catch, coastal development, and highly variable food availability. Various Pacific populations have vanished entirely from certain regions, for instance Malaysia.

Source: National Geographic

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