by Sujata Gupta
Turtles are being relocated from the US Gulf coast to save them from the Deepwater Horizon oil spill – but this may scramble their navigating skills, marine biologists warn. As a result, the animals could lose their way to their nursery grounds.
The turtles – mostly threatened loggerheads, as well some endangered Kemp's ridley, greenand leatherback turtles – use the Earth's magnetic field to navigate often hazardous migration routes. They travel from their birthing beaches of Florida and Alabama to the open sea and then on to their nursery grounds around the Azores and Canary Islands, where they live for years before returning to their home beaches to nest as adults.
The first batch of evacuated sea turtles, rescued as eggs from the oil-drenched Florida Panhandle and Alabama beaches, to hatch at Kennedy Space Center in Florida were released into the Atlantic Ocean on Saturday. The evacuation was part of a campaign spearheaded by the US Fish and Wildlife Service to move all Gulf coast turtles' eggs – there are at least 50,000 – from their native breeding grounds to the unaffected Atlantic shores of Florida.
The eggs are being evacuated 50 to 53 days after laying, in the final stages of their 60-day incubation. Immediately after hatching they will be released along Florida's Atlantic beaches. But some researchers are warning that releasing Gulf coast turtles straight onto the sand on the other side of Florida could interfere with their navigational skills.
All at sea
The turtles' internal mapping abilities could become scrambled, cautions Nathan Putman, who studies migration patterns in sea turtles at the University of North Carolina at Chapel Hill.
To save the turtles from getting lost at sea, Putman and Ken Lohmann, who runs the marine biology team at the university, suggest an alternative: "Why not place them into an area that is thought to be part of their normal migratory route?" asks Lohmann.
They argue that more turtles would survive if they were released at sea directly into the Gulf Stream, the Atlantic current that originates at the tip of Florida. "That's where they're likely to wind up anyway," says Lohmann.
His view is backed up by evidence that suggests turtles are programmed from birth to follow a specific migratory path once in water. Indeed, turtles from different nesting sites seem to inherit different sets of navigational instructions.
And that means a turtle born in the Gulf but displaced to the Atlantic coast may follow the wrong path out to the open ocean, Lohmann says.
Not that way
"There's a distinct possibility that those hatchlings will perform differently in response to the currents," agrees Colin Limpus, a turtle biologist and scientific adviser for the UN's Convention on Migratory Species.
Wallace "J." Nichols, a biologist with the California Academy of Sciences in San Francisco and Ocean Conservancy, based in Washington DC, agrees with Putman and Lohmann's suggestion of releasing the turtles at sea: "If you're taking the time to move them that many miles, get them out where they would be going anyway," he says.
Chuck Underwood, a spokesman for the Fish and Wildlife Service, says that releasing the turtles on sand allows scientists to assess how they are coping with the move. The process also mimics turtles' natural behaviour. "We're trying to be as natural as we can," he says.
The agency is concerned that if the turtles remain on the Gulf coast they may all perish, Underwood adds: "You're likely to have at least some success and some success is better than zero."
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