Leatherback sea turtle

The leatherback sea turtle (Dermochelys coriacea), sometimes called the lute turtle, leathery turtle or simply the luth, is a large species of sea turtle. The largest of all living turtles and the heaviest non-crocodilian reptile, it reaches lengths of up to 2.7 metres (8 ft 10 in) and weights of 500 kilograms (1,100 lb). 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. Leatherback turtles have a global range, although there are multiple distinct subpopulations. The...

Leatherback sea turtles can be found primarily in the open ocean. Scientists tracked a leatherback turtle that swam from Jen Womom beach of Tambrauw Regency in West Papua of Indonesia to the US in a 20,000 km (12,000 mi) foraging journey over a period of 647 days. Leatherbacks follow their jellyfish prey throughout the day, resulting in turtles "preferring" deeper water in the daytime, and shallower water at night (when the jellyfish rise up the water column). This hunting strategy often places turtles in very frigid waters. One individual was found actively hunting in waters where temperatures were as low as 0.4 °C (32.7 °F). Following each foraging dive, the leatherback would return to warmer (17.5 °C (63.5 °F)) surface waters to regain body heat before continuing to dive into near-freezing waters. Leatherback turtles are known to pursue prey deeper than 1000 m—beyond the physiological limits of all other diving tetrapods except for beaked whales and sperm whales. Their favored breeding beaches are mainland sites facing the deep water, and they seem to avoid those sites protected by coral reefs.

United States

Adult D. coriacea turtles subsist almost entirely on jellyfish. Due to their obligate feeding nature, leatherbacks help control jellyfish populations. Leatherbacks also feed on other soft-bodied organisms, such as other cnidarians (siphonophores), tunicates (salps and pyrosomas) and cephalopods (squid). They are also believed to feed on small crustaceans (amphipods and crabs), fish (possibly symbiotes with jellies), sea urchins, snails, seagrasses, and algae. Adult turtles consume 73% of their body weight daily. Pacific leatherbacks migrate about 6,000 mi (9,700 km) across the Pacific from their nesting sites in Indonesia to eat California jellyfish. During these long traveling periods, Remora remora (common remoras) will latch onto leatherbacks and display phoresis behavior or 'hitchhiking'; this represents commensalism, where one species is benefiting while the other species is not gaining or losing anything. One cause for their endangered state is plastic bags floating in the ocean. Pacific leatherback sea turtles mistake these plastic bags for jellyfish; an estimated one-third of adults have ingested plastic. Plastic enters the oceans along the west coast of urban areas, where leatherbacks forage, with Californians using upward of 19 billion plastic bags every year. Plastic bags were banned in California in 2016. Several species of sea turtles commonly ingest plastic marine debris, and even small quantities of debris can kill sea turtles by obstructing their digestive tracts. Nutrient dilution, which occurs when plastics displace food in the gut, affects the nutrient gain and consequently the growth of sea turtles. Ingestion of marine debris and slowed nutrient gain leads to increased time for sexual maturation that may affect future reproductive behaviors. These turtles have the highest risk of encountering and ingesting plastic bags offshore of San Francisco Bay, the Columbia River mouth, and Puget Sound.

Very little is known of the species' lifespan. Some reports claim "30 years or more", while others state "50 years or more" and upper estimates exceed 100 years. In 2020, researchers from CSIRO, Australia's National Science Agency, developed a method to calculate the natural lifespan of vertebrate animals by leveraging genetic markers and known lifespans of various species. From the genomic sequencing of DNA samples taken from five different marine turtle species, the natural lifespan of the leatherback turtle was calculated as being 90.4 years.

Dermochelys coriacea is the only species in genus Dermochelys. The genus, in turn, contains the only extant member of the family Dermochelyidae. Domenico Agostino Vandelli named the species first in 1761 as Testudo coriacea after an animal captured at Ostia and donated to the University of Padua by Pope Clement XIII. In 1816, French zoologist Henri Blainville coined the term Dermochelys. The leatherback was then reclassified as Dermochelys coriacea. In 1843, the zoologist Leopold Fitzinger put the genus in its own family, Dermochelyidae. In 1884, the American naturalist Samuel Garman described the species as Sphargis coriacea schlegelii. The two were then united in D. coriacea, with each given subspecies status as D. c. coriacea and D. c. schlegelii. The subspecies were later labeled invalid synonyms of D. coriacea. Both the turtle's common and scientific names come from the leathery texture and appearance of its carapace (Dermochelys coriacea literally translates to "Leathery Skin-turtle"). Older names include "leathery turtle" and "trunk turtle". The common names incorporating "lute" and "luth" compare the seven ridges that run the length of the animal's back to the seven strings on the musical instrument of the same name, but are more likely derived from the lute's ribbed back which is in the form of a shell. Leatherbacks have been viewed as unique among extant reptiles for their ability to maintain high body temperatures using metabolically generated heat, or endothermy. Initial studies on their metabolic rates found leatherbacks had resting metabolisms around three times higher than expected for reptiles of their size. However, recent studies using reptile representatives encompassing all the size ranges leatherbacks pass through during ontogeny discovered the resting metabolic rate of a large D. coriacea is not significantly different from predicted results based on allometry. Rather than using a high resting metabolism, leatherbacks appear to take advantage of a high activity rate. Studies on wild D. coriacea discovered individuals may spend as little as 0.1% of the day resting. This constant swimming creates muscle-derived heat. Coupled with their countercurrent heat exchangers, insulating fat covering, and large size, leatherbacks are able to maintain high temperature differentials compared to the surrounding water. Adult leatherbacks have been found with core body temperatures that were 18 °C (32 °F) above the water in which they were swimming. Leatherback turtles are one of the deepest-diving marine animals. Individuals have been recorded diving to depths as great as 1,280 m (4,200 ft). Typical dive durations are between 3 and 8 minutes, with dives of 30–70 minutes occurring infrequently. They are also the fastest-moving reptiles. The 1992 edition of the Guinness Book of World Records lists the leatherback turtle moving at 35.28 km/h (21.92 mph) in the water. More typically, they swim at 1.80–10.08 km/h (1.12–6.26 mph).

The leatherback turtle population in the Atlantic Ocean ranges across the entire region. They range as far north as the North Sea and to the Cape of Good Hope in the south. Unlike other sea turtles, leatherback feeding areas are in colder waters, where an abundance of their jellyfish prey is found, which broadens their range. However, only a few beaches on both sides of the Atlantic provide nesting sites. This population seems to be female dominated. Off the Atlantic coast of Canada, leatherback turtles feed in the Gulf of Saint Lawrence near Quebec and as far north as Newfoundland and Labrador. The most significant Atlantic nesting sites are in Suriname, Guyana, French Guiana in South America, Antigua and Barbuda, and Trinidad and Tobago in the Caribbean, and Gabon in Central Africa. The beaches of Mayumba National Park in Mayumba, Gabon, host the largest nesting population on the African continent and possibly worldwide, with nearly 30,000 turtles visiting its beaches each year between October and April. Off the northeastern coast of the South American continent, a few select beaches between French Guiana and Suriname are primary nesting sites of several species of sea turtles, the majority being leatherbacks. A few hundred nest annually on the eastern coast of Florida. In Costa Rica, the beaches of Gandoca and Parismina provide nesting grounds.

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, however, turtle-fishery interactions may play a larger role than previously recognized. 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. Leatherback sea turtles ranging from 1885 to 2007 were autopsied for the existence of plastic in the gastrointestinal tract. It was discovered that 34% of the cases had plastic blockage. Due to their diet consisting of gelatinous zooplankton, the leatherback sea turtle consumes high amounts of salt. Different life stages of dead individuals from the western Atlantic Ocean were used to test the concentrations of various contaminants found in the salt glands and red blood cells. These contaminants include arsenic, cadmium, lead, mercury, and selenium. The contaminants were found in higher concentrations in the blood compared to the salt gland secretions. The length of the curve in the carapace of a turtle had a direct correlation with cadmium and mercury concentrations. Salt glands and red blood cells are potentially susceptible to high levels of contaminants being found in the oceans.

Dermochelys coriacea is the only species in genus Dermochelys. The genus, in turn, contains the only extant member of the family Dermochelyidae. Domenico Agostino Vandelli named the species first in 1761 as Testudo coriacea after an animal captured at Ostia and donated to the University of Padua by Pope Clement XIII. In 1816, French zoologist Henri Blainville coined the term Dermochelys. The leatherback was then reclassified as Dermochelys coriacea. In 1843, the zoologist Leopold Fitzinger put the genus in its own family, Dermochelyidae. In 1884, the American naturalist Samuel Garman described the species as Sphargis coriacea schlegelii. The two were then united in D. coriacea, with each given subspecies status as D. c. coriacea and D. c. schlegelii. The subspecies were later labeled invalid synonyms of D. coriacea. Both the turtle's common and scientific names come from the leathery texture and appearance of its carapace (Dermochelys coriacea literally translates to "Leathery Skin-turtle"). Older names include "leathery turtle" and "trunk turtle". The common names incorporating "lute" and "luth" compare the seven ridges that run the length of the animal's back to the seven strings on the musical instrument of the same name, but are more likely derived from the lute's ribbed back which is in the form of a shell.