39.1 Thursday, Jan. 5 Navigating the Atlantic Ocean with Geomagnetic Markers: An Inherited Magnetic Map in Hatchling Loggerhead Sea Turtles LOHMANN, K. J.*; PUTMAN, N. F.; LOHMANN, C. M. F.; University of North Carolina at Chapel Hill; University of North Carolina at Chapel Hill; University of North Carolina at Chapel Hill KLohmann@email.unc.edu
Young loggerhead sea turtles (Caretta caretta) from eastern Florida undertake a transoceanic migration in which they gradually circle the north Atlantic Ocean before returning to the North American coast. Hatchlings begin the migration with a ‘magnetic map’ in which regional magnetic fields function as navigational markers and elicit changes in swimming direction at crucial locations along the migratory route. Orientation responses are elicited by at least eight different magnetic fields that exist at widely separated geographic areas. The direction of swimming elicited by each field appears to be suitable for helping turtles remain within the warm waters of the North Atlantic subtropical gyre and advance along the migratory pathway. The results demonstrate that the magnetic map of young loggerhead turtles is remarkably complex and flexible. Turtles can derive both longitudinal and latitudinal information from the Earth’s field, and responses appear suitable for helping turtles exploit favorable ocean currents for migratory transport in at least some oceanic areas. The magnetic map also appears to be inherited, inasmuch as regional magnetic fields elicit orientation responses in turtles that have never migrated or even been in the ocean. These findings imply that hatchling turtles from different populations in different parts of the world are likely to have magnetic navigational responses uniquely suited for the migratory routes that each group follows. Thus, from a conservation perspective, turtles from different populations are probably not interchangeable.