The giant leatherback sea turtle, Dermochelys coriacea, is the biggest turtle species still in the world. They are a giant amongst most other modern reptiles, the only ones bigger are three of the remaining species of crocodilians.
In addition to being very large, one thing that is immediately noticeable is that they don’t possess a bony shell, like most other turtle species. They are instead covered in a thick layer of “leather” and fat, hence their name — the Giant Leatherback Turtle. They have what is considered to be the most hydrodynamic body design of any living turtle, which is part of what allows them to reach speeds of up to 22 mph, making them the fastest moving reptile in the world.
On average Dermochelys coriacea adults tend towards around 6.0–7.2 feet in total length, and towards a weight of around 550 to 1,500 lbs. They can reach much, much larger than that though. The biggest one reported in modern times was over 9.8 feet when measured from head to tail, with a carapace longer than 7.2 feet, and weighing in at about 2,000 lbs. That individual was found on a beach on the west coast of Wales.
They are the last remaining species in the genus Dermochelys, and are likely headed towards extinction themselves. They are currently listed as critically endangered, with only an estimated 26,000 to 43,000 mature females left, spread out across all of the oceans of the world. Their numbers have fallen drastically during the last century, the primary causes being: the exploitation of their nests/eggs by humans, being caught as by-catch by fishing boats, being killed by boat collisions, and diseases/deaths caused by the chemical/physical pollution released by human activity.
Exploitation of turtle nests has been one of the most significant factors in the species’ global population decline. Almost total collapse of many local nesting populations has occurred throughout most of Southeast Asia. Their flesh is not to the taste of many people though, so they are not typically hunted, except on the sustenance level. They are regularly caught as by-catch though, because they are so large that ‘turtle excluder devices’ tend to be ineffective. An estimated 1,500 mature females were being caught accidentally every year during the 1990s. Perhaps more significant than any of that though, is the effect that human-caused pollution is having on them. Many turtles die from the malabsorption and intestinal blockage that results from the ingestion of balloons and plastic bags, which greatly resemble the jellyfish that they prey on. And chemical pollution has also been found to be having a significant effect on them, very high levels of phthalates have been measured in their eggs’ yolks.
Something else that is worth noting, is that turtles are one of the few animals to prey on jellyfish, with a decline in their numbers, jellyfish numbers tend to rocket upwards, as they have in recent years.
Some other interesting facts about them:
– They don’t have teeth, instead possessing spines throughout their throats which stop prey from escaping after being eaten. As the awesome picture below shows.
– They are very well adapted to life in cold waters: possessing an extensive layer of brown fat tissue, “temperature independent swimming muscles, counter-current heat exchangers between the large front flippers and the core body, as well as an extensive network of counter-current heat exchangers surrounding the trachea.”
– Leatherbacks are almost unique among reptiles with regards to their ability to maintain a high body temperatures via the use of metabolically generated heat, being, in a way, warm-blooded. But rather than maintain a high body temperature via a high resting metabolism, like mammals do, giant leatherbacks turtles instead use a very 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 counter-current 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 they were swimming in.”
– They are one of the deepest diving marine animals alive currently. They have been recorded reaching depths of over 4,200 feet.
– They live all over the world, possessing the widest distribution of any still living turtle species. “D. coriacea has the widest distribution, reaching as far north as Alaska and Norway and as far south as the Cape of Good Hope in Africa and the southernmost tip of New Zealand. The leatherback is found in all tropical and subtropical oceans, and its range extends well into the Arctic Circle.”
– The giant leatherback turtle is divided amongst three major, genetically distinct populations. These populations reside in the Atlantic, eastern Pacific and western Pacific Oceans.
– They are seen primarily in the open ocean. Researchers once tracked a leatherback turtle that “swam from Indonesia to the U.S. in a 12,000 mile foraging journey over a period of 647 days.”
– “Adult D. coriacea turtles subsist almost entirely on jellyfish. Due to their obligate feeding nature, leatherback turtles help control jellyfish populations. Leatherbacks also feed on other soft-bodied organisms, such as tunicates and cephalopods,” according to Wikipedia.
– “An estimated one third of adult giant leatherback sea turtles have ingested plastic. Plastic enters the oceans along the west coast of urban areas, where leatherbacks forage; with Californians using upwards of 19 billion plastic bags every year. 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.”
– How long they live is currently something of a mystery. Some researchers estimate up to 80 years, while others estimate a likely average of 30-45. There is not any good reason to say that they could not live for considerably longer than that though. Some turtle species have very long lifespans.
– Because of their size and aggressive nature they have very few natural enemies. It has been observed though that they can occasionally be “overwhelmed and preyed on by very large marine predators such as orcas, great white sharks and tiger sharks.” At sea they are known to aggressively defend themselves, sometimes attacking boats.
– Interestingly, while most other sea turtle species will nearly always return to the beach that they hatched at to lay their eggs, leatherbacks actually sometimes choose a different beach within the same region to lay their eggs.
– “The typical nesting environment includes a dark forested area adjacent to the beach. The contrast between this dark forest and the brighter, moonlit ocean provides directionality for the females. They nest towards the dark and then return to the ocean and the light.”
– “Leatherback nesting seasons vary by location; it occurs from February to July in Parismina, Costa Rica. Farther east in French Guiana, nesting is from March to August. Atlantic leatherbacks nest between February and July from South Carolina in the United States to the United States Virgin Islands in the Caribbean and to Suriname and Guyana.”
– “Adult 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 hatchings scrambling for the sea. Once they enter the water, they become prey to predatory fish and cephalopods. Very few survive to adulthood.” Those that do though, grow to be massive animals, with very few predators.
Current estimates state that the Giant Leatherback Turtle could be extinct within 20 years, almost entirely as a result of human activity.