The leatherback sea turtle, Dermochelys coriacea, is the largest living turtle species. Unlike other sea turtles, it lacks a hard, bony shell, instead possessing a flexible, leathery carapace, which gives it its name. Adults can reach over 2.7 meters (8.9 feet) in length and weigh up to 1,000 kilograms (2,200 pounds). These attributes are integral to its adaptation to open ocean life and contribute to its extraordinary swimming prowess.
Specialized Anatomy for Swimming
The leatherback’s physical makeup supports its swimming capabilities. Its flexible carapace, covered by thick, oily flesh and leather-like skin with embedded osteoderms, withstands high hydrostatic pressures during deep dives. This streamlined, teardrop-shaped body design reduces drag as the turtle moves through water.
Its large, paddle-shaped front flippers are proportionally the biggest among all sea turtles, reaching up to 2.7 meters (8.9 feet) in large individuals. These powerful limbs provide efficient propulsion. A thick layer of insulating fat, coupled with its large body size, helps leatherbacks regulate their body temperature, allowing them to venture into colder regions than most other sea turtles.
Leatherbacks also possess a specialized blood vessel structure known as a counter-current heat exchange system. This system, where warm arterial blood flowing from the heart runs alongside colder venous blood returning from the extremities, allows heat transfer, helping the turtle maintain a body temperature higher than the surrounding water. This physiological adaptation enables them to forage in sub-polar waters and prevents overheating in tropical environments.
The Mechanics of Their Powerful Swim
Leatherback turtles employ a distinctive “flight” or “rowing” swimming style. Both their large front flippers move simultaneously in a powerful, synchronous stroke, unlike the alternating strokes seen in other sea turtle species. This coordinated motion generates both lift and thrust, making them highly efficient long-distance swimmers.
During power-stroking, propulsion occurs for approximately 30% of the limb beat, with the remaining 70% involving a power-saving glide. This glide maintains swimming velocity due to the animal’s large mass and low drag coefficient. The downstroke is faster than the upstroke, generating forward thrust during both phases, though the downstroke produces greater thrust. This efficient technique allows leatherbacks to reach speeds of up to 22 miles per hour and sustain endurance over vast distances.
Epic Migrations and Deep Dives
The swimming capabilities of leatherback turtles enable them to undertake extensive migratory journeys, covering thousands of miles across ocean basins annually. Some individuals travel over 10,000 miles a year between tropical nesting beaches and colder feeding grounds. Western Pacific leatherbacks, for example, make a nearly 7,000-mile trans-Pacific journey from nesting beaches in areas like Indonesia to foraging grounds off the U.S. coast.
Beyond their migrations, leatherbacks are also deep divers. They are the deepest diving sea turtle species, routinely descending to depths exceeding 1,000 meters (3,280 feet), with the deepest recorded dive reaching 1,344 meters (4,409 feet). These dives can last for significant durations, with some individuals remaining submerged for up to 90 minutes.
Their shell can compress under intense pressure, and they can absorb nitrogen through their carapace, which helps prevent decompression sickness. They also possess large oxygen stores in their blood and muscles, and can regulate blood flow to conserve oxygen. These deep excursions are thought to allow them to scan the water column for food resources or oceanographic features.