Leatherback Sea Turtle

## Description

The leatherback sea turtle (Dermochelys coriacea ), sometimes called the lute turtle or leathery turtle or simply the luth, is the largest of all living turtles and the heaviest non-crocodilian reptile, reaching lengths of up to 1.8 metres and weights of 500 kg. It is the only living species in the genus Dermochelys and family Dermochelyidae. It can easily be differentiated from other modern sea turtles by its lack of a bony shell; instead, its carapace is covered by oily flesh and flexible, leather-like skin, for which it is named.

## Appearance

Leatherback turtles have the most hydrodynamic body of any sea turtle, with a large, teardrop-shaped body. A large pair of front flippers powers the turtles through the water. Like other sea turtles, the leatherback has flattened forelimbs adapted for swimming in the open ocean. Claws are absent from both pairs of flippers. The leatherback's flippers are the largest in proportion to its body among extant sea turtles. Leatherback's front flippers can grow up to 2.7 m (8.9 ft) in large specimens, the largest flippers (even in comparison to its body) of any sea turtle.The leatherback has several characteristics that distinguish it from other sea turtles. Its most notable feature is the lack of a bony carapace. Instead of scutes, it has thick, leathery skin with embedded minuscule osteoderms. Seven distinct ridges rise from the carapace, crossing from the cranial to caudal margin of the turtle's back. Leatherbacks are unique among reptiles in that their scales lack β-keratin. The entire turtle's dorsal surface is colored dark grey to black, with a scattering of white blotches and spots. Demonstrating countershading, the turtle's underside is lightly colored. Instead of teeth, the leatherback turtle has points on the tomium of its upper lip, with backwards spines in its throat (esophagus) to help it swallow food and to stop its prey from escaping once caught.

## Distribution

Leatherbacks are primarily pelagic animals. They travel great distances from their nesting beaches to their feeding grounds. Although leatherbacks are most often found in tropical waters, they are distributed around the globe in temperate oceans, and even on edges of subarctic water. The leatherback sea turtle travels further north than any other sea turtle. They live in Northern Atlantic waters as far north as Newfoundland, Nova Scotia, and Labrador. They also inhabit South Atlantic Waters, as far south as Argentina and South Africa. This turtle inhabits waters as far east as Britain and Norway.During the nesting season they are discovered along the coasts of French Guiana, Suriname, Guyana, Trinidad, Gabon, West Africa, Parque Marino Las Baulas in Guanacaste, Costa Rica, Papua New Guinea, Andaman and Nicobar Islands, Thailand, in the U.S. on St. Croix, U.S. Virgin Islands, and in Puerto Rico and Florida. The largest nesting colony is in Africa, along the coast of French Guiana. More than 7,000 females laid as many as 50,000 eggs there in 1988 and again in 1992. There is one nesting record in Cape Lookout, North Carolina.

## Behavior

Leatherbacks are mostly solitary. They migrate great distances between nesting and feeding grounds. They seem to locate locations that have high concentrations of jellyfish, and feed near the surface or dive to find the highest concentrations of prey.

## Diet

Leatherback turtles are carnivores that feed in the open ocean. Their main prey are gelatinous invertebrates, mainly jellyfish and salps. They are known to eat other kinds of food though, including small crustaceans and fish (possibly symbiotes with jellies), cephalopods, sea urchins, and snails.Leatherbacks do not have the powerful muscles and hard crushing jaw apparatus that some other sea turtles have for eat hard-shelled prey. Instead they have sharp-edged jaws for biting soft-bodied prey. The esophagus in this species is lined with short spines that point downstream, preventing jellies from escaping once swallowed.

## Reproduction

Mating takes place at sea. Males never leave the water once they enter it, unlike females, which nest on land. After encountering a female (which possibly exudes a pheromone to signal her reproductive status), the male uses head movements, nuzzling, biting, or flipper movements to determine her receptiveness. Males can mate every year but the females mate every two to three years. Fertilization is internal, and multiple males usually mate with a single female. This polyandry does not provide the offspring with any special advantages.Female leatherbacks are known to nest up to 10 times in a single nesting season giving them the shortest internesting interval of all sea turtles.

## Population

### Conservation

Leatherback turtles have few natural predators once they mature; they are most vulnerable to predation in their early life stages. Birds, small mammals, and other opportunists dig up the nests of turtles and consume eggs. Shorebirds and crustaceans prey on the hatchlings scrambling for the sea. Once they enter the water, they become prey to predatory fish and cephalopods.
Leatherbacks have slightly fewer human-related threats than other sea turtle species. Their flesh contains too much oil and fat to be considered palatable, reducing the demand. However, human activity still endangers leatherback turtles in direct and indirect ways. Directly, a few are caught for their meat by subsistence fisheries. Nests are raided by humans in places such as Southeast Asia. In the state of Florida, there have been 603 leatherback strandings between 1980 and 2014. Almost one-quarter (23.5%) of leatherback strandings are due to vessel-strike injuries, which is the highest cause of strandings.
Light pollution is a serious threat to sea turtle hatchlings which have a strong attraction to light. Human-generated light from streetlights and buildings causes hatchlings to become disoriented, crawling toward the light and away from the beach. Hatchlings are attracted to light because the lightest area on a natural beach is the horizon over the ocean, the darkest area is the dunes or forest. On Florida's Atlantic coast, some beaches with high turtle nesting density have lost thousands of hatchlings due to artificial light.
Many human activities indirectly harm Dermochelys populations. As a pelagic species, D. coriacea is occasionally caught as bycatch. Entanglement in lobster pot ropes is another hazard the animals face. As the largest living sea turtles, turtle excluder devices can be ineffective with mature adults. In the eastern Pacific alone, a reported average of 1,500 mature females were accidentally caught annually in the 1990s. Pollution, both chemical and physical, can also be fatal. Many turtles die from malabsorption and intestinal blockage following the ingestion of balloons and plastic bags which resemble their jellyfish prey. Chemical pollution also has an adverse effect on Dermochelys. A high level of phthalates has been measured in their eggs' yolks.

## References

https://animalia.bio/leatherback-sea-turtle

https://animaldiversity.org/accounts/Dermochelys\_coriacea/