LOHMANN, Kenneth J.; LOHMANN, Catherine M.F.; University of North Carolina at Chapel Hill; University of North Carolina at Chapel Hill: A Coastal Magnetic Map Used in Sea Turtle Navigation

Sea turtles navigate long distances to specific geographic areas used as feeding grounds and nesting sites, but how they do so has remained enigmatic. It has been hypothesized that the position-finding sense of sea turtles is based at least partly on information derived from the Earth�s magnetic field, and that turtles navigating along continental coastlines can move toward specific destinations by sensing subtle differences in the fields that exist at different geographic locations. To determine if turtles do indeed use a magnetic map sense to navigate toward target areas, juvenile green turtles (Chelonia mydas) captured in their feeding grounds along the east coast of Florida, U.S.A., were tethered inside a large magnetic coil system and exposed to magnetic fields replicating those that exist at specific locations along the southeastern U.S. coast. Turtles tested in a field that exists north of the capture site oriented southward, whereas those tested in a field that exists south of the capture site oriented northward. The results provide strong evidence that sea turtles possess a magnetic positioning system that is capable of helping them navigate to specific coastal locations used as feeding sites. The same mechanism may be used by adult turtles to navigate to nesting locations.