The largest sea turtle in the world is the Leatherback Sea Turtle (Dermochelys coriacea).
Identifying the Largest Species
The Leatherback Sea Turtle is the largest of all living turtle species. This distinction is based on both its weight and the length of its carapace, the upper shell. Average adults weigh between 800 and 1,500 pounds, though the largest recorded individual reached over 2,000 pounds (900 kilograms).
Its curved carapace can reach up to 7 feet (2.2 meters) in length. The next largest species, the Green Sea Turtle, averages around 300 to 400 pounds. The Leatherback’s bulk helps it maintain body temperature in cold waters, contributing to its expansive global range.
Unique Biological Characteristics
The Leatherback is the sole surviving member of the ancient family Dermochelyidae. Its defining feature is its carapace, which is not made of hard, bony scutes like other species. Instead, it consists of a mosaic of dermal bones beneath thick, rubbery skin, giving it a leathery texture.
This flexible shell structure is an adaptation for deep diving, allowing the carapace to compress under intense hydrostatic pressure. The species routinely descends to depths exceeding 3,000 feet (1,000 meters), with the deepest recorded dive reaching nearly 4,000 feet (1,250 meters). The Leatherback also possesses regional endothermy, using its large size, thick fat layer, and specialized circulatory system to maintain a core body temperature warmer than the surrounding water.
Global Habitats and Feeding Ecology
The Leatherback Sea Turtle holds the record for the widest global distribution of any reptile. They are found in all the world’s oceans except the Arctic and Antarctic, ranging from the tropics where they nest to temperate and sub-polar waters where they forage. These migrations, sometimes covering over 10,000 miles (16,000 kilometers) annually, are driven by their specialized diet.
Their diet consists almost entirely of soft-bodied invertebrates like jellyfish and sea squirts. They possess backward-pointing spines lining their esophagus to retain this slippery prey. This dependence on gelatinous plankton means the turtles must follow the seasonal blooms of their prey, often leading them into colder, more northern waters. A consequence of this diet is the frequent mistake of ingesting plastic bags, which resemble jellyfish and can cause fatal blockages in their digestive system.
Status in the Wild
The global conservation status of the Leatherback Sea Turtle is listed as Vulnerable by the International Union for Conservation of Nature (IUCN). This global assessment masks the state of certain populations, particularly those in the Pacific, which are classified as Critically Endangered. Pacific populations have seen declines of over 80 percent in the last three generations.
Threats are linked to human activity across both marine and terrestrial environments. Accidental entanglement in commercial fishing gear (bycatch) is a leading cause of mortality. On nesting beaches, the collection of eggs for human consumption and the loss of nesting habitat due to coastal development pose significant challenges. Climate change also presents a long-term threat by affecting the temperature of nesting sand, which determines the sex of hatchlings.