by Muhammad Akhir Ariffin

Created on: January 07, 2009

For most of the year, the green turtles of Brazil spend their time in protected bays along the Atlantic coast. They feed on underwater fields on the grass, chomping with their horny, serrated, beak like jaws or bolting down seaweed fronds without chewing them.

Along the same stretches of coast there are beaches free from predators that would be ideal places for the turtles to lay their eggs. Instead in January, many turtles head out to sea against the powerful South Equatorial Current and swim 1250 miles to lay their eggs on the beaches of Ascension Island. They mate at sea before they go ashore. Ascension 34sq miles in extent, is a tiny dot in the Atlantic midway between Africa and South America. Yet the turtles about 3 ft long, find their way back to the same beach from which they had scuttled as hatchlings years before. Not all Brazilian green turtles make this journey only those that hatched on Ascension Island. It takes them six or seven weeks to reach their destination, swimming at a rate of about 30 miles a day. And all this without food. Scientist can only speculate on how the turtles find their way and why they go so far.

Any guidance system must keep the turtles on a direct course difficult if, when the turtles is swimming it pushes harder with one flipper than the other, or if it is dragged one side by barnacles growing on it shell. There are several navigational techniques a turtles could use. It could swim against westward flowing South Equatorial Current or with the eastward flowing counter current 350 ft down. Alternatively it could taste the water and climb an "odour ladder", the smell of Ascension strengthening as it swims eastwards. Or it could continually pinpoint its points against the earth's magnetic field. Then there is celestial guidance. The turtles must go to the surface regularly to breathe, so each time it could take a bearing from the sun or from the moon and stars. The most intriguing aspect of the turtle's behavior however is why they go to Ascension at all. One explanation offered involves earth's constantly changing geology.

Ancestors of today green turtles were living at the time of the dinosaurs, more than 100 million years ago. When small mammal began to appear on the scene, some were very partial to turtle's egg, so sea turtles sought out remote, robber free, island beaches to lay their eggs. At that time, Africa and South America were closed together with the Atlantic just a narrow strip between. But as volcanic lava was trust

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