Leatherbacks are the largest turtles on Earth, growing up to seven feet long and exceeding 2,000 pounds. These reptilian relics are the only remaining representatives of a family of turtles that traces its evolutionary roots back more than 100 million years. Once prevalent in every ocean except the Arctic and Antarctic, the leatherback population is rapidly declining in many parts of the world.
While all other sea turtles have hard, bony shells, the inky-blue carapace of the leatherback is somewhat flexible and almost rubbery to the touch. Ridges along the carapace help give it a more hydrodynamic structure. Leatherbacks can dive to depths of 4,200 feet — deeper than any other turtle—and can stay down for up to 85 minutes.
Unlike their reptilian relatives, leatherbacks are able to maintain warm body temperatures in cold water by using a unique set of adaptations that allows them to both generate and retain body heat. These adaptations include large body size, changes in swimming activity and blood flow, and a thick layer of fat.
Leatherbacks undertake the longest migrations between breeding and feeding areas of any sea turtle, averaging 3,700 miles each way. After mating at sea, females come ashore during the breeding season to nest. The nighttime ritual involves excavating a hole in the sand, depositing around 80 eggs, filling the nest, leaving a large, disturbed area of sand that makes detection by predators difficult, and finally returning to the sea.
It is estimated that only about one in a thousand leatherback hatchlings survive to adulthood. Eggs are often taken by humans from nests to be consumed for subsistence or as aphrodisiacs. Many leatherbacks fall victim to fishing lines and nets, or are struck by boats. Leatherbacks also can die if they ingest floating plastic debris mistaken for their favorite food: jellyfish.
Leatherbacks are currently designated as endangered under the U.S. Endangered Species Act. The number of leatherbacks in the Atlantic appears to be stable or increasing, but the Pacific population is declining at an alarming rate due to egg harvest, fishery bycatch, coastal development, and highly variable food availability. Some Pacific populations have disappeared entirely from certain areas, such as Malaysia.