Reptiles
Leatherback Sea Turtle
Dermochelys coriacea · also called leatherback, lute turtle, leathery turtle
The leatherback is a sea turtle unlike any other — larger, deeper-diving, warmer-bodied, and stranger. It has no hard shell, it eats a diet of pure jellyfish, and it ranges from the equator to the edge of the polar ice.
Overview
Leatherbacks are the most widely distributed reptile on Earth, and among the most migratory of all animals. Individuals tracked by satellite have crossed entire ocean basins — Pacific leatherbacks swim from Indonesian nesting beaches to feeding grounds off California, and Atlantic ones travel between Caribbean beaches and the seas off Canada and West Africa. They spend almost their whole lives in the open ocean, coming ashore only to nest.
A different kind of turtle
The leatherback split from all other sea turtles more than 100 million years ago, and it shows:
- No bony shell of plates. Instead, a flexible carapace of small bones set in a thick, rubbery, oil-rich skin, drawn out into seven long ridges that improve streamlining.
- A warm body in cold water. Its bulk, insulating fat, heat-exchanging blood vessels, and constantly working muscles keep it far warmer than the sea around it.
- Extreme diving. Leatherbacks routinely dive past 1,000 metres and have been recorded below 1,200 — deeper than sperm whales usually go — collapsing their lungs and slowing their hearts to cope with the pressure.
- A jellyfish-processing throat. Sharp-edged jaws and rows of stiff, backward-facing spines down the oesophagus grip gelatinous prey.
Diet
Leatherbacks are jellyfish specialists. They follow blooms of jellyfish and related plankton across the ocean and eat almost constantly, because such watery prey yields little energy per bite. This tight link to jellyfish is also the source of a major threat: a drifting plastic bag looks very much like a jellyfish, and ingested plastic is common in stranded leatherbacks.
Reproduction
Every two to four years a female returns to the region where she hatched, comes ashore at night on a tropical beach, digs a deep nest, and lays around 80 fertile eggs plus a number of smaller yolkless ones. She may nest several times in a season. Incubation takes about two months, and — as in other sea turtles — nest temperature determines sex, with warmer sand producing females. Hatchlings dash to the sea and are not seen again until near maturity; where the juveniles spend those years, “the lost years,” is still largely unknown.
Threats and conservation
The leatherback is Vulnerable globally, with the East Pacific and Southwest Atlantic populations Critically Endangered after catastrophic declines. Fisheries bycatch, egg poaching, coastal development, artificial light that disorients hatchlings, vehicle traffic on beaches, and plastic pollution are the main drivers. Conservation successes — such as the strong recovery of nesting in parts of the North Atlantic — show that protecting nesting beaches, patrolling against poachers, and modifying fishing gear (circle hooks, turtle excluder devices) can work when applied consistently.
Leatherback Sea Turtle: common questions
How big is a leatherback turtle?
It is the biggest turtle alive and the fourth-heaviest living reptile, after three crocodiles. A typical adult is 1.5 to 1.8 metres of shell and 250 to 700 kilograms; the largest ever found, washed up in Wales in 1988, was nearly 3 metres long and weighed 916 kilograms. Leatherbacks are far larger than any hard-shelled sea turtle.
How does a cold-blooded turtle survive in freezing water?
Through a set of adaptations sometimes called "gigantothermy." Its huge body loses heat slowly, it has a thick layer of oily fat, its flippers and throat use counter-current blood vessels that trap warmth in the core, and its swimming muscles generate heat constantly. Together these let a leatherback keep its body many degrees warmer than seas close to freezing, so it can forage in waters no other sea turtle can enter.
What do leatherbacks eat?
Almost nothing but jellyfish and similar soft, gelatinous animals like salps and siphonophores. Because jellyfish are mostly water and provide little energy, a leatherback must eat enormous quantities — estimates run to hundreds of kilograms, roughly its own body weight, per day. Its scissor-like jaws and a throat lined with backward-pointing spines are built to handle slippery, stinging prey.
Why are leatherbacks endangered?
Several pressures at once. They drown in longline and gillnet fishing gear as bycatch; their eggs are heavily poached on many nesting beaches; beachfront development, lighting, and vehicles degrade nesting habitat; and they frequently eat floating plastic bags, mistaking them for jellyfish, which can block the gut. The East Pacific population has collapsed by more than 90% since the 1980s.