Each year in early July, when loggerhead turtle eggs start hatching on the shores of eastern Florida, Ken and Catherine Lohmann pack a van full of computers, coolers, and lab equipment and rumble down the road to Boca Raton, Florida. They are going there to learn how turtle hatchlings find their way to sea. The turtles are headed for the North Atlantic gyre, a system of warm-water currents that spans the Atlantic between the eastern coast of North America and the western coast of Africa. The turtles may linger there for years, feeding on seaweed, until they grow large enough to return to American feeding grounds without fear of predators near the shore.
Navigational skills are crucial.
A turtle straying off course at the north end of the gyre could wash up on the shores of Great Britain, shocked with a lethal dose of cold North Atlantic water. A turtle swimming south out of the gyre could be swept up in south Atlantic currents and carried away from its range. How the turtles find their way back to the nesting ground has long been a mystery. But part of the answer, the Lohmanns believe, lies in the turtles' ability to orient themselves through the magnetic field of the earth. The loggerhead hatching season lasts through September, but the Lohmanns have only six to seven weeks to conduct their research before the UNC-CH fall semester starts.