Turtle, Leatherback Sea

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Turtle, leatherback sea

Dermochelys coriacea

phylum: Chordata

class: Reptilia

order: Testudines

family: Dermochelyidae

status: Critically endangered, IUCN Endangered, ESA

range: Oceanic

Description and biology

The leatherback is the largest sea turtle in the world. An average adult can measure up to 5 feet (1.5 meters) long and weigh between 800 and 1,000 pounds (363 and 454 kilograms). Other marine turtles have hard, bony-plated shells, or carapaces (pronounced KAR-a-paces). The dark brown to black carapace of the leatherback sea turtle is made of seven raised ridges that are soft and rubbery. Its front flippers are exceptionally long and powerful. When extended, they may span over 8 feet (2.4 meters). The turtle's head and neck are dark brown or black with white or yellowish blotches.

Powerful swimmers, leatherbacks spend most of their lives at sea. They have special physical adaptations—including a thick layer of insulating fat—that allows them to stay under-water for long periods of time. Having relatively weak jaws, the turtles feed almost entirely on jellyfish, often consuming twice their weight each day.

Female leatherback sea turtles lay their eggs at different times of the year, depending on their location. Those who build nests at North Atlantic sites lay their eggs between April and July. Those at eastern Pacific sites lay theirs between November and January. After mating with a male offshore, a female leatherback crawls up on a sandy, undisturbed beach at night and digs a shallow body-pit with all four limbs. She then digs out a nest cavity about 40 inches (102 centimeters) deep with her hind limbs. She lays a clutch (eggs produced at one time) of about 100 round, white-shelled eggs in the nest, covers them with sand, then returns to the ocean.

After 56 to 65 days, the eggs hatch and the young leatherbacks, measuring 2 to 2.5 inches (5 to 6.4 centimeters) long, emerge from the nest and crawl toward the ocean. Very few survive to adulthood. Pigs, lizards, and other predators (including humans) prey on the eggs. Before they even reach the ocean, young leatherbacks are preyed upon by birds and small mammals. In the water, both young and adult leatherbacks are preyed upon by sharks.

Habitat and current distribution

Leatherback sea turtles are among the most wide-ranging of sea animals, inhabiting waters from the tropics to the subarctic. They migrate vast distances to and from nesting sites. Female leatherbacks prefer to nest on relatively undisturbed beaches that have a heavy surf and deep water immediately offshore. These sites are usually located on tropical beaches in the Atlantic, Indian, and Pacific Oceans. Sometimes the turtles gather in temperate (mild) waters where jellyfish are more abundant.

Since males do not come ashore, it is almost impossible for biologists (people who study living organisms) to estimate how many currently exist. But since females do, biologists are able to count them. In the 1980s and 1990s, it was estimated that about 100,000 nesting females existed around the world. A 2000 survey showed more than 80 percent decline in nesting in the Pacific populations of the species. Estimates suggest that there has been a 70 percent reduction in the global population of adult females in less than one generation.

History and conservation measures

During the 1960s, biologists believed the leatherback sea turtle was on the verge of extinction. The turtle's population has since increased and declined. It faces many threats, including the loss of its coastal nesting habitats, entrapment in fishing nets, poaching of its eggs, and poisoning from plastics.

Many areas that were once leatherback nesting sites have been converted into living areas for humans or developed into tourist areas. Other nesting sites have been destroyed as off-road vehicles and the development of nearby land have caused beach erosion.

Turtles and other large sea animals are often caught in shrimp-fishing nets and drown. It is estimated that 11,000 sea turtles, many of them leatherbacks, are trapped this way each year. To prevent this from happening, many nets have turtle excluder devices or TEDs built into them. A TED is a grid of bars with an opening at either the top or the bottom. This grid is fitted into the neck of a shrimp net. Small sea animals like shrimp pass easily through the bars into the bag end of the net. Large sea animals like turtles strike the bars and are ejected back out through the opening. TEDs safely remove about 97 percent of the turtles that become trapped in the shrimp nets. However, shrimpers complain that TEDs reduce the amount of shrimp they are able to catch. In the early 2000s, the U.S. government closed a large area in the Pacific Ocean to U.S. longline fishery (fishing with a line up to several miles long with a series of baited hooks along its length) in order to protect leatherbacks from being captured accidentally.

Although leatherback sea turtle meat is oily and not very appetizing, some people along the turtle's range do hunt the animal. Its eggs are especially prized in Malaysia. International trade of all sea turtle products is forbidden under the Convention on International Trades in Endangered Species (CITES), but some nations allow the use of leatherback sea turtle meat, oil, and eggs.

Plastic trash in the ocean, such as clear sandwich bags, is a grave concern because leatherbacks cannot distinguish between jellyfish and clear plastic. Recent examinations found that many turtles had plastic in their stomachs. Biologists do not know how much plastic it takes to kill a leatherback sea turtle, but no amount is beneficial, and the oceans are becoming more polluted with plastics every day.