Leatherback turtles

Leatherback turtles are magnificent animals whose lineage dates from a time before the dinosaurs.

These huge, mysterious creatures are the largest of the sea turtles. They grow to nearly 10ft in length and over 900kg (nearly a ton), though most adults are about 6ft. Their name comes from their leathery carapace made of a thin but very tough and rubbery skin, strengthened by thousands of bonelets beneath.

Like all sea turtles, the leatherback is endangered. They numbered about 115,000 in 1980, but by some estimates the population may now be less than 25,000. In Trinidad, and at some other locations, their numbers are increasing, but there have been massive declines elsewhere, attributed in part to harvesting of their eggs by humans for food and entanglement in fishing nets.

Leatherbacks are predominantly ocean dwellers and have been found as far north as Alaska and as far south as Chile. They remain active at temperatures too cold for other reptiles and so are thought to be able to regulate their body temperature. They can dive to great depths, more than 3,300 ft (as deep as any whale), and can stay underwater for nearly 30 minutes at a time. If a further reason for liking leatherback turtles were needed, it would be their prodigious appetite for jellyfish - in captivity they can consume twice their own bodyweight each day. Squid is also on the menu.

Though they are known to travel 3,000 miles from their nesting sites, about every 2 or 3 years the female leatherback returns to her ancestral beach to lay her eggs. Leatherbacks prefer sloping sandy beaches where they can make a short haul to dry sand; here they excavate a metre-deep egg chamber using their back flippers. Their sheer bulk makes this a tremendous effort. While laying is in progress the turtles go into a trance-like state. In the deepest part of the chamber they lay about 80 white leathery eggs the size of snooker balls, followed by a layer of sand and 30 smaller unfertilised decoy eggs in case the nest is uncovered and raided.

Once she has laid, the female covers the nest using her flippers, leaving a distinctive circular sweeping pattern in the sand. She will then haul herself to other areas of the beach to laboriously create similar patterns at different spots in an effort to hide the position of her true nest. Towards dawn she returns exhausted to the sea. She may come back to lay again up to 10 times each season.

About 65 days later, the hatchlings emerge and dash for the sea. The mortality rate is high at every stage. Only 60% of eggs mature into hatchlings as many are infertile or are dug up by dogs or poachers, many fall prey to dogs or birds on their way to the sea, or are then eaten by fish.

On Trinidad the nesting process can be seen between March and August, and the hatchlings emerge between May and September. Turtle laying beaches are protected areas and you need a permit to enter after dark. It is a very moving experience to watch the females laying - hire a local naturalist guide, keep quiet, and stay well back until the female enters her egg-laying trance. Some say that then she may even be touched, but this is not recommended.

Photos can be taken in dawn light (rather than by flash at night).

Please support the excellent work of the Turtle Protection Programme of the Toco Foundation, which provides wardens to protect the laying beaches by night and day and to guide visitors.