Meeting Abstract

3.1  Jan. 4  Detection of Coastal Magnetic Fields by Sea Turtles: a Possible Mechanism Underlying Natal Homing LOHMANN, K. J.*; HORNER, A. J.; AKINS, L.; LOHMANN, C. M. F.; Univ. of North Carolina at Chapel Hill; Univ. of North Carolina at Chapel Hill; Univ. of North Carolina at Chapel Hill; Univ. of North Carolina at Chapel Hill KLohmann@email.unc.edu

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. Later, as adults, the turtles exhibit natal homing on a regional scale, returning to nest in the same general geographic area where they themselves hatched. Young sea turtles are known to use the magnetic fields that exist in different oceanic regions as a system of open-sea navigational markers. In principle, such fields might also function in helping turtles return to nest in the coastal areas where they themselves hatched. As a first step toward investigating this possibility, hatchling turtles were exposed to two different magnetic fields that mark coastal areas in north and south Florida. Hatchlings responded to the field from the northern site by swimming approximately southeast, a response that might serve to help turtles move farther into the Gulf Stream and reduce the chances of being swept into fatally cold water that lies to the north. In contrast, hatchlings exposed to the field from the southern site, where there is no danger of displacement from the migratory route, were not significantly oriented. The orientation elicited by the two fields was significantly different. Thus, by the time they enter the ocean, hatchling turtles already possess the ability to distinguish among magnetic fields that exist in different nesting areas along the Florida coast. The precision with which turtles can resolve differences among fields is, in principle, sufficient to account for the known resolution of natal homing in Florida loggerheads.