Largest among all the sea turtle species, leatherbacks get their name from the their unique shell, which is composed of a layer of thin, tough, rubbery skin strengthened by thousands of tiny bone plates that make it appear “leathery”. Leatherbacks are known to travel great distances, and dive the deepest, when compared to other sea turtles.
Leatherbacks are the largest marine turtles in the world, growing up to 170 cm in length and weighing up to 500 kg. The species leaves track marks about 150- 200 cm wide, deep and broad, with symmetrical diagonal marks made by forelimbs, usually with a deep median groove, which is formed by the long tail.
The leathery dark grey to black carapace is mottled with white or pale spots, while the plastron is whitish to black and marked by 5 ridges. Hatchlings have white blotches on the carapace.
Species: D. coriacea
Leatherbacks have delicate, scissor-like jaws, which permit the species to feed exclusively on soft-bodied animals. A leatherback’s diet comprises entirely of jellyfish. That an animal such as the leatherback can sustain itself on jellyfish, which is nutrient poor and largely comprised of water is remarkable. Mostly pelagic in nature, leatherbacks are also known to forage closer to the coasts. Thermoregulatory adaptations such as a counter-current heat exchange system, high oil content, and large body size helps maintain a core body temperature higher than that of the surrounding water, thereby allowing them to tolerate colder water temperatures. Unlike other sea turtle species, leatherback females may change nesting beaches, though they tend to stay in the same region. Leatherbacks usually nest once in every 2 to 3 years, though there have been reports of them nesting annually. A female may nest between 6 to 9 times per season, with an average gap of 10 days between nestings. A clutch consists of an average of 80 fertilised eggs, which are covered with a layer of about 30 smaller, unfertilised eggs in each nest. Incubation takes about 65 days. Eggs measure about 5 cm in diameter.
Leatherbacks prefer open access beaches with a steep slope and rock free deep water approach. However, such open beaches with little shoreline protection are vulnerable to beach erosion triggered by seasonal changes in wind and wave direction. The largest remaining nesting assemblages of leatherbacks are found on the coasts of northern South America and West Africa.
Leatherbacks are the most migratory and wide ranging of all sea turtles. They are found in the Gulf of Alaska and south of the Bering Sea in the northern Pacific; to Chile in the southeastern Pacific; in the Barents Sea, Newfoundland and Labrador in the North Atlantic; throughout the Indian Ocean; and to Tasmania and New Zealand in the south-western Pacific. Their thermoregulatory adaptations (see biology) permit them to travel to the extreme north.
In India, they are found in the Andaman and Nicobar Islands, mainly the Great Nicobar Island. The main nesting sites are Galathea on the east coast and several beaches on the west coast of Great Nicobar.
Leatherbacks are listed as Critically Endangered by the IUCN. The greatest threat to the species has been to the eggs, which remains as much of a threat today. The species has rarely been hunted for its meat. Scientists suggest that gill-net and long line fisheries are also a growing threat to the species.
Indian Wildlife (Protection) Act: Schedule I
IUCN Red list: Critically Endangered (http://www.iucnredlist.org/apps/redlist/details/6494/0)