Secret of sea turtle navigation discovered

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CHAPEL HILL, N.C., Feb. 24 (UPI) -- U.S. scientists say they've discovered how sea turtles are able to navigate while migrating across thousands of miles of open oceans with no visual landmarks.

Researchers at the University of North Carolina say they've determined loggerhead sea turtles apparently can determine their longitude location at sea using two sets of magnetic cues, the BBC reported Thursday.

Several species of turtles are known to use magnetic cues to determine latitude, but it had been believed that this wasn't possible for longitude.

Loggerhead turtles have developed a method that involves using the strength and angle of the Earth's magnetic field, researchers say.

"The most difficult part of open-sea navigation is determining longitude or east-west position," lead researcher Nathan Putnam says.

"It took human navigators centuries to figure out how to determine longitude on their long-distance voyages."

Loggerhead hatchlings manage this feat as soon as they reach the sea from their nests, Putnam says, then spend several years successfully navigating complex migratory routes across thousands of miles of ocean.

"Along the migratory route of loggerheads, nearly all regions are marked by unique combinations of intensity (field strength) and inclination angle (the angle that field lines intersect the surface of the Earth)," he says.

"Thus, turtles can determine longitudinal position by using pairings of intensity and inclination angle as an X, Y coordinate system."