The Pacific population of leatherback sea turtles has suffered most over the last twenty years: as few as 2,300 adult females now remain, making the Pacific leatherback the world's most endangered marine turtle population.

Although Atlantic populations are rather more stable, scientists believe that they, too, will decline due to the large numbers of adults being killed accidentally by fishing fleets. In the Atlantic, the fact that they are widely distributed during the migration process increases the risk of interaction of leatherback turtles with longline fisheries.

The leatherback turtle is the largest marine turtle and one of the largest living reptiles. Leatherbacks are one of the most migratory of all marine turtle species, making both trans-Atlantic and trans-Pacific crossings. They are easily distinguished by their carapace, which is leathery, not hard as in other turtles, and by their long front flippers.

Leatherbacks have a unique system of blood supply to their bones and cartilage. This enables their body temperature to stay several degrees above the water temperature and allows them to tolerate cold water, rather like a mammal. They can dive to depths of up to 1,200m, much deeper than any other marine turtle.

Recent DNA analysis confirms that Atlantic and Pacific populations are genetically distinct lineages of a single species. In turn, nesting Pacific leatherback populations are separated into two genetically distinct populations (eastern and western populations).

Size

The leatherback can reach up to 180cm, and 500kg in weight.

Colour

The species carapace (shell) is dark with white spots.

Life Cycle

Juvenile leatherbacks may remain in tropical waters warmer than 26°C, near the coast, until they exceed 100cm in curved carapace length. Adults are pelagic and live in the open ocean, sometimes in temperatures below 10°C.

Breeding

Female leatherbacks may lay 4 to 5 times per season, each time depositing 60 to 120 eggs. Leatherbacks appear to nest once every two or three years with an incubation period of approximately 60 days.

Diet

The large size of leatherbacks is all the more remarkable given their low energy, low protein diet of soft-bodied creatures such as jellyfish, squid and tunicates ("jelly fish-like" marine invertebrates).

Previous Population and Distribution

The global population for this species was estimated to be 115,000 adult females in 1982. By 1996 this had been revised down to about 30-40,000. Leatherback populations in the Pacific and Indian Oceans have undergone dramatic declines in the past forty years. For example, the nesting colony at Terengganu, Malaysia went from more than 3,000 females in 1968, to 20 in 1993, to just 2 in 1993 - there are no signs of recovery.

Similar scenarios have occurred in Indonesia, Sri Lanka, Thailand, and Mexico. Numbers of females recorded at four formerly major Pacific rookeries have declined to about 250 in Mexico, 117 in Costa Rica, two in Malaysia, and fewer than 550 in Indonesia.

Current Population and Distribution

Leatherbacks have been recorded as far north as Alaska, and as far south as Africa's Cape of Good Hope.

The Pacific may now have as few as 2,300 adult females.

Effective Protection

However, not all leatherback populations have declined: in southern Africa, three decades of strong protection have increased the small annual nesting population more than fourfold. Recent reports mention that west Africa has an important population with around 10,400 nests per season, but the total area occupied for the leatherbacks is not well known and there is no available historical information on nesting trends of this population.

The most important nesting beaches now remaining in the Atlantic are found in Suriname, French Guiana, and Gabon. In the Pacific, the few remaining important beaches are in Indonesia, Mexico and Costa Rica, with other rookeries found in Nicaragua, Panama and Guatemala.

The main threats which affect marine turtles are:

• Habitat loss and degradation
• Wildlife trade
• Collection of eggs and meat for consumption
• Incidental capture (bycatch)
• Climate change
• Pollution

A paper published in 1983 stated that almost 100% of leatherback eggs in Thailand were poached, while in some areas the egg harvest and illegal poaching has removed more than 95% of the clutches. This has been recognized as the main cause (together with fisheries mortalities and poor hatcheries practices) for the collapse in the Malaysia population. There are now few large populations from which eggs could be collected in the western Pacific.

• Send a turtle to rehab! Help the recuperation process for thousands of sick and injured turtles.
• Don't buy products which have been made from sea turtle parts. Guitars, ashtrays, jewellry and other products made from sea turtles are sold to tourists around the world.