Imagine if we could carry our homes on our backs wherever we went. What fun that would be. After a tiring day we would not have to fight traffic and crowds to get home, and when we needed protection we could simply slip inside.

We cannot do that, but the turtle can. It has a hard shell on its back and belly, and that shell is its home. When it needs to, the turtle draws its head, tail and legs into the shell, and puts them out again when it wants. Scientists say, according to the writer, that turtles are the oldest surviving creatures among the reptiles, and have witnessed the world's events for 160 crore years.

In English, the animal Bengali calls kachchhap is a tortoise or a turtle. Those that live on land are tortoises and those that live in water are turtles. Tortoises go into water only when they have to, and turtles come on to land only when they have to.

Water-dwelling turtles are of two kinds by habitat: sea turtles and freshwater turtles. Of the seven species of sea turtle, five are found along the Bay of Bengal coast. Their legs are shaped like paddles, so they swim easily, using the front pair most and the hind pair to change direction. Unlike freshwater turtles and land tortoises, they cannot pull their head, tail and legs into the shell. They eat everything from vegetation and algae upwards.

The olive ridley is one of the five sea turtle species of Bangladesh, India and the wider Asian subcontinent. It is found in good numbers off Hatiya, Sandwip and the Andaman Islands in the Bay of Bengal, and also in the Pacific and Atlantic oceans. Coastal indigenous people call it "gadha kachhua". Its upper shell is broad; in adults it is olive-green and the lower shell pale yellow, while hatchlings are grey. It eats almost anything: fish, crabs, prawns, jellyfish and starfish, and it feasts on snails, oysters and sea urchins.

A female olive ridley is ready to lay eggs at ten to twelve years old. At laying time she comes ashore, mostly near mangrove forests along the coast. Males never come on land. Folklore says a grown female returns to lay eggs at the very spot where she hatched, and the writer says research has borne this out: half the DNA in the nucleus of a female's cells comes from her father and half from her mother, but the DNA in her mitochondria comes only from her mother, and turtles that return year after year to the same spot all have identical DNA.

Females travel several thousand kilometres by sea every year to lay. A female lives 65-70 years and comes ashore to lay 30-40 times, laying about a hundred eggs each time, or 3,000-4,000 eggs in a lifetime. Only one per cent of the hatchlings, just 30 to 40, survive to adulthood.

The females do not scatter their eggs here and there. They arrive in their thousands, lay together and leave together. Scientists believe this mass behaviour helps them survive: with so many females, eggs and hatchlings in one place, enough are likely to live even after predators have taken what they want.

The writer lists the world's important olive ridley nesting grounds as two on the Pacific coast of Costa Rica, one on the coast of Mexico, one in the Indian state of Odisha, and one at a beach called Gahirmatha on the Bay of Bengal coast. More than five lakh females come to lay on the Odisha coast every year, making it the largest olive ridley breeding ground in the world.

Each female, weighing 60-70kg, crawls about 25 metres inland from the high-tide line, digs a pit to her own size with her flippers and settles into it so that only her back shows. She lays 100 to 150 eggs, quickly, at about ninety an hour, then covers them with sand.

The eggs hatch 54 to 56 days later, although the hatchlings take another four to six days to dig their way out, usually at night. Because they hatch together, thousands of young turtles race in the dark towards the sea glittering in the moonlight, a beautiful sight. Once in the water, no one knows where they go until they reappear ten to twelve years later to lay eggs. Researchers believe the young probably live on tiny jellyfish and sea urchins in shallow water, and as adults make homes in the crevices of coral reefs or in undersea caves.

The problem is that the olive ridley is now heading for extinction, its numbers falling for many reasons. In Chile, Mexico, Costa Rica, the United States and other countries, fishermen must fit their nets with a turtle-excluding device the writer calls "tedgriji". With it attached, only fish are caught: the device pushes a trapped turtle out of the net by another route. In the United States and Mexico, only fishermen whose nets carry the device are given a government fishing permit card, and they must show it to fish and to sell their catch. On this subcontinent, fishermen have still not begun to use the device.

As tourism has grown, countless hotels, resorts and houses have sprung up right against the high-tide line along the coasts of Bangladesh and neighbouring India, close to the turtles' breeding grounds, and the turtles are losing them. Drawn by bright street and house lights at night, many hatchlings head inland instead of to the sea and die. Dogs, jackals, kites, hawks and crows destroy many eggs and young.

The turtle's greatest enemy is surely people. Heavy oil pollution at sea is blinding many olive ridleys, making them easy prey on land. Tourists and poachers have taken away the solitude they need, so many turtles return to the sea without laying. Widespread destruction of coastal forest is another major reason their breeding grounds are shrinking.

The olive ridley is beautiful to look at and remarkable in its habits, crossing thousands of kilometres of sea each year to lay eggs on just four stretches of coast in the world. Yet through greed and thoughtless hunting, this peaceful, harmless species, 160 crore years old by the writer's account, is now nearly extinct. Its needs are tiny next to ours: a quiet place by the sea and an unpolluted shore for two months a year. Even that we fail to give. Unless the surviving breeding grounds are seriously protected now, the writer warns, the olive ridley will vanish from the earth this century, and even if the turtles forgive us, nature never will.

The writer is a science writer, researcher and MPhil scholar at Dhaka University.

Source: Jagonews24. First published in Bengali on The Agro News.