Christmas with the leatherbacks

Larry Greenemeier, Scientific American 24 Dec 09;

Want to know where Noelle and Darwinia—two intrepid adult female leatherback turtles (Dermochelys coriacea) that nest in Gabon—are spending their Christmas? Researchers at the University of Exeter in the U.K. have made it easy by launching a new Web site on Wednesday that uses satellite tracking technology to monitor the turtles' movements off the coast of west central Africa.

The turtles are each traveling solo but have logged about 1,287 kilometers between them since the researchers began tracking on December 7. The transmitters allow the researchers to determine the turtles' positions when they surface to breathe.

The story of Noelle and Darwinia is more a story of survival than of their progress, as the waters around Gabon are increasingly subject to industrial fishing, pollution and oil exploitation, particularly from nations outside western Africa, including countries in Europe, according to the researchers. "It is only by having detailed information on where these creatures go that we can try to protect them," Exeter postdoctoral researcher Matthew Witt said in a prepared statement.

During three nesting seasons, scientists conducted land and aerial surveys along Gabon's 600-kilometer coast, estimating that a population of up to 41,373 female turtles uses the nesting beaches. Gathering information about leatherbacks when they are at sea is not as easy, given that they are the deepest diving of all sea turtles. Researchers have recorded dives of up to 1.2 kilometers, on par with the dives of sperm whales.

Leatherbacks—the largest of all sea turtles, generally measuring up to nearly two meters long and weighing up to 540 kilograms—saw their population in the Indo-Pacific region diminish by more than 90 percent in the 1980s and 1990s. Although the International Union for Conservation of Nature (IUCN) issued a report (pdf) last week indicating that leatherbacks (along with the Artic fox and koala) are "the species destined to be hardest hit by climate change," the Exeter researchers say there is a lack of information about their populations in much of the Atlantic, especially near Africa.

The IUCN reports that the "critically endangered" turtles are being affected by rising sea levels and increased storm activity due to climate change destroying their nesting habitats on beaches. Temperature increases may also lead to a reduction in the proportion of males relative to females. The sex of leatherbacks is determined by the temperature of eggs during incubation. With leatherbacks, temperatures above 29 degrees Celsius result in female hatchlings.

The Exeter researchers are working with Gabon's government and a number of NGOs working there, including the Wildlife Conservation Society and Seaturtle.org, to learn more about the leatherbacks' movements.

"Over the Christmas period we will follow their movements with great interest with the hope that the information we gather can feed into truly useful approaches to help promote the protection of the species," Witt said.