Sea turtles are a diverse group of reptiles that have navigated the world’s oceans for over 100 million years. These ancient mariners play an important role in marine ecosystems, contributing to the health of seagrass beds and coral reefs through their feeding habits. There are seven distinct species of sea turtles recognized today, each adapted to various marine environments from warm tropical waters to colder regions.
The Leatherback Sea Turtle
The largest of all living turtles is the leatherback sea turtle (Dermochelys coriacea). This reptile can reach lengths of up to 2.7 meters (8.9 feet) and weigh over 900 kilograms (2,000 pounds). The largest recorded leatherback weighed 916 kilograms (2,019 pounds) and measured 2.56 meters (8.4 feet) long. Its immense dimensions make it the heaviest non-crocodilian reptile on Earth. To put its size into perspective, a leatherback can be as long as a small car and weigh as much as a compact vehicle.
Unique Adaptations and Global Habitats
Unlike other sea turtles that possess a hard, bony shell, the leatherback is distinguished by its flexible, leathery carapace. This shell is composed of a mosaic of small, interlocking bones covered by a thick layer of oily flesh and rubbery skin. This unique shell structure allows the leatherback to withstand the extreme pressures of deep ocean dives, reaching depths of nearly 1,200 meters (4,000 feet), deeper than most marine mammals.
Leatherbacks have a specialized diet consisting primarily of jellyfish, which their unique mouth and throat, lined with backward-pointing spines, are perfectly adapted to consume. Despite being cold-blooded reptiles, they exhibit thermoregulatory abilities, allowing them to maintain a warmer body temperature than the surrounding water. This adaptation, which includes a thick layer of insulating fat and a countercurrent heat exchange system, enables them to thrive in colder waters inaccessible to other sea turtle species.
These turtles are highly migratory, undertaking some of the longest migrations of any marine animal. They travel thousands of miles between tropical nesting beaches and colder foraging grounds across the Atlantic, Pacific, and Indian Oceans. For example, Western Pacific leatherbacks can embark on journeys of up to 11,400 kilometers (7,000 miles) across the Pacific to feed off the U.S. coast.
Conservation Status and Threats
Despite their massive size and widespread distribution, leatherback sea turtles face threats, leading to their classification as “Vulnerable” globally by the IUCN. Some populations, particularly in the Pacific, are critically endangered due to sharp declines in recent decades. A danger is entanglement in fishing gear, such as longlines and nets, which can lead to drowning.
Plastic pollution poses another threat, as leatherbacks often mistake plastic bags and debris for jellyfish, their primary food source, leading to blockages in their digestive systems. Habitat loss and degradation at nesting sites, driven by coastal development and rising sea levels, also impact their survival. Climate change also affects their reproductive success, as rising sand temperatures on nesting beaches can skew hatchling sex ratios, potentially leading to a lack of male turtles. Efforts to protect these turtles include the use of Turtle Excluder Devices (TEDs) in fishing nets and the establishment of protected nesting and foraging areas.