Save the Leatherback Turtle

Save the Leatherback Turtle

The world's largest sea turtle faces threats from every direction — and conservationists are racing to keep it alive

A. The leatherback sea turtle, Dermochelys coriacea, is the world's largest reptile and the most widely distributed of all sea turtle species, ranging across every ocean from the tropics to sub-polar waters. Unlike other sea turtles, which have hard, bony shells covered with scales, the leatherback is encased in a mosaic of tiny bone fragments embedded in firm, rubbery skin — an anatomical structure that allows its body to withstand the immense pressures encountered at depth and to maintain a body temperature several degrees warmer than the surrounding water, enabling it to function in cold seas where other turtles cannot survive.

B. Leatherbacks undertake some of the longest migrations of any animal on Earth. Individuals tracked by satellite have been recorded travelling over 20,000 kilometres between their nesting beaches in the tropics and their feeding grounds in productive sub-polar waters, crossing entire ocean basins in single migrations. Female leatherbacks return to the same beaches where they hatched to lay their own eggs — a pattern of natal homing mediated by the Earth's magnetic field that allows them to locate specific sections of coastline across thousands of kilometres of open ocean. This fidelity to natal beaches makes them particularly vulnerable to changes in the availability or quality of nesting habitat.

C. The leatherback's diet is almost exclusively jellyfish and other gelatinous zooplankton, an unusual food source that most animals cannot exploit effectively because of the low caloric content relative to the large quantities that must be consumed. Leatherbacks compensate for this through specialised throat anatomy — backward-pointing spines lining the oesophagus that prevent jellyfish from escaping once swallowed — and through their extraordinary diving ability, which allows them to follow jellyfish into the deep scattering layer during daytime and pursue them to the surface at night. They are capable of diving to depths exceeding 1,200 metres and can remain submerged for over 85 minutes.

D. Leatherback populations have declined severely over the past fifty years. The Pacific D Leatherback populations have declined severely over the past fifty years. The Pacific population — which nests primarily on beaches in Mexico and Costa Rica and feeds in the North Pacific — has fallen by more than 95 percent from its mid-twentieth century peak, and some nesting beaches that supported thousands of nesting females annually in the 1980s now receive only a few dozen. The main drivers of this decline include the incidental capture of leatherbacks in fishing gear — particularly longline fisheries targeting swordfish and tuna — and the harvesting of eggs from nesting beaches, which was widespread until the introduction of legal protections but continues illegally in some areas.

E. A major emerging threat is plastic pollution. Leatherbacks visually identify jellyfish by their shape and translucency as they float in the water column, and floating plastic bags, balloons, and other transparent or translucent debris are apparently indistinguishable to them from jellyfish prey. Post-mortem examinations of stranded leatherbacks find plastic debris in the majority of individuals, and in some cases the quantity of plastic present is sufficient to cause blockages or perforations of the digestive tract. As plastic production and ocean plastic accumulation continue to increase, the scale of this threat is expected to grow.

F. Conservation programmes for leatherbacks focus on protecting nesting females and eggs, reducing bycatch in fisheries, and addressing the threats faced by turtles on their feeding grounds. Beach protection programmes — ranging from community- based egg protection schemes to government-managed nest monitoring and relocation — have achieved significant reductions in egg harvesting at many nesting sites. The modification of fishing gear — including the use of circle hooks rather than J-hooks in longline fisheries, which reduce turtle bycatch rates — has been adopted in some national fisheries following negotiations between conservation groups and the fishing industry. The enforcement of these measures in international waters and across multiple jurisdictions remains a significant challenge.

G. The Atlantic and Indian Ocean populations of leatherback are in considerably better condition than the Pacific population and, with sustained protection, show some signs of recovery at key nesting sites. The divergent trajectories of different leatherback populations illustrate a broader truth about marine conservation: the difference between recovery and extinction often depends on the consistency and coverage of protection over long timescales and across the full geographic range of the species. Leatherbacks are long-lived animals whose females do not reach sexual maturity until around fifteen years of age — meaning that the consequences of reduced juvenile survival may not become visible in nesting numbers for more than a decade, and that recovery from reduced breeding populations will take many decades even under optimal conditions.