Study tracks turtles journey across South Atlantic

Sylvia Hui, Associated Press Yahoo News 4 Jan 11;

LONDON – Leatherback turtles swim for thousands of miles across the South Atlantic to get to their feeding grounds, a trip that takes some of them 150 days to complete, researchers said Wednesday.

The findings are important for conservationists looking to protect the turtles from threats such as fishing nets and hooks, which have been blamed for the dramatically depleted population of leatherbacks in the Pacific Ocean, researchers said.

"All of the routes we've identified take the leatherbacks through areas of high risk from fisheries, so there's a very real danger to the Atlantic population," said Brendan Godley, a professor in conservation biology at the University of Exeter.

The five-year study followed the movement of female turtles from the world's largest breeding colony in Gabon, central Africa, as they swam to feeding grounds across the South Atlantic. Once the turtles reach a food-rich habitat, they will stay there for up to five years to build up reserves to reproduce and return to Gabon once they are ready to mate again.

Researchers attached electronic satellite tracking equipment to the backs of 25 female turtles, as they finished nesting on beaches and were returning to the sea.

One female was tracked making a 7,563 kilometer (4,699 mile) journey traveling in a straight line across the South Atlantic from Africa to South America, said Matthew Witt, a marine biologist who took part in the study. At a pace of 50 kilometers a day, that trip took about 150 days of consistent swimming, he said.

"Despite extensive research carried out on leatherbacks, no one has really been sure about the journeys they take in the South Atlantic until now," Witt said. "From a human perspective, the South Atlantic is a vast, vast area. When challenged with that path, how is it that you can get across it and not get lost? I think that's fantastic."

The study identified three migratory routes, taking the turtles from Central Africa to Brazil, Uruguay, Argentina and down the coast off southern Africa. But why individual turtles choose one route over another remains one of the biggest questions in sea turtle biology, Witt said.

There are more leatherback turtles in the Atlantic than in the Pacific, where populations have declined dramatically over the past three decades. The exact cause of the dwindling numbers is not clear, although turtle egg harvesting, coastal net fishing and longline fishing have been blamed.

Witt said that the study helped identify 11 nations in the South Atlantic whose territorial waters the turtles pass through, and that those countries could take the lead on marine conservation efforts.

The research was published in the Proceedings of the Royal Society B on Wednesday.

Tracking a Mysterious Giant: Epic Turtle Migrations
Andrea Mustain LiveScience.com 4 Jan 11;

The leatherback turtle is the colossus of the turtle world. They can grow up to 6.5 feet (2 meters) long and weigh in at 1,190 pounds (540 kilograms). Yet despite their heft, these giant reptiles are elusive.

Leatherbacks spend years at sea, and, although populations in the Pacific and North Atlantic oceans have been tracked, the ocean whereabouts of the world's largest population of leatherbacks in other ocean basins has remained a mystery.

"Nobody really had any idea of where they were going in the South Atlantic," said Matthew Witt, a post-doctoral research fellow at the University of Exeter in England.

Now, with the help of satellites, Witt has provided researchers with the first glimpse of the critically endangered turtles' epic migrations in the region.

Nighttime searches

Even with the high-tech space tools, tracking the gigantic turtles was a hands-on business for Witt.The turtles had to be tagged with transmitters before they could be tracked.

Witt spent several weeks a year walking deserted beaches in Gabon, on Africa's central Atlantic coast, searching through the dead of night for his large quarry - nesting female leatherbacks.

Gabon's coast is home to more than 40,000 leatherbacks, according to some estimates, yet finding females to tag with a satellite transmitter wasn't easy. Witt would typically walk 12.5 miles (20 kilometers) a night, finding his way by starlight and moonlight - artificial lights disturb the turtles, Witt said - in search of disturbances in the sand, a telltale sign a female was nearby.

"They're huge, great things," Witt told OurAmazingPlanet. "Even at a few hundred meters you can see their tracks coming out of the sea and onto the beach."

Sending sand flying, and accompanied by a fair amount of noise - they grunt a lot, Witt said - the turtles dig nests about 3 feet (1 meter) down into the sand, chambers that typically contain about 100 eggs.

While a turtle is actually laying its eggs, it goes very quiet and still, Witt said, providing 20 or 25 minutes in which to attach a transmitter to a female's leathery back.

During a reproductive season, female leatherbacks lay about 1,000 eggs in about 90 days, an energy-intensive process.

Once finished, the females return to the high seas, where they must spend three or four years feeding and building up strength before they again return to land, for another exhausting round of nest-digging and egg-laying.

Three routes

Over the course of his five-year study, Witt tracked 25 females along three distinct routes in the Atlantic. Witt said he hopes that the new findings on where these massive turtles spend their time will be used to better focus conservation efforts.

Although some Atlantic populations appear to be doing well, the Pacific leatherback population has dropped a staggering 98 percent since the 1980s.

Much of the decline is due to human interference - egg collection is a problem, and the turtles are also snared in fishery lines.

Tracking the turtles with satellite transmitters is key for researchers, Witt said, but also creates a sort of dilemma.

"You need to collect this information, because you need it to help manage and conserve them," Witt said, "but you don't want to be too invasive, because there are such a limited number of them."