Meeting Abstract

66.3  Saturday, Jan. 5  Ontogeny of navigational responses to regional magnetic fields in loggerhead sea turtle hatchlings BROTHERS, J.R.*; ERNST, D.A.; HANKINS, K.; LOHMANN, K.J.; University of North Carolina, Chapel Hill; University of North Carolina, Chapel Hill; University of North Carolina, Chapel Hill; University of North Carolina, Chapel Hill

Hatchling loggerhead sea turtles (Caretta caretta) from the east coast of Florida enter the ocean and immediately begin a long distance migration lasting several years. During this time, many of the turtles circle the Sargasso Sea before eventually returning to the North American coast. Young loggerheads are known to begin their migration with a “magnetic map” in which regional magnetic fields existing along the migratory route serve as open-sea navigational markers and elicit changes in swimming direction at critical points in the migration. Little is known, however, about whether the magnetic fields turtles experience early in their migration influence orientation responses to subsequent regional magnetic fields. As a first step toward investigating, we tested the orientation responses of two groups of turtles with different “magnetic histories” to a field that exists near northern Portugal (north of the normal migratory route). Turtles that had previously swum only in the magnetic field of their home beach failed to show a consistent directional preference when tested in the north Portugal field. In contrast, turtles that had previously swum in a magnetic field that exists near South Carolina (a location along the early migratory pathway) responded to the same north Portugal field by swimming approximately southwest, a direction that might help them remain within the warm-water migratory pathway. These results suggest that experience with magnetic fields that exist along the migratory route can influence subsequent responses to regional magnetic fields under at least some conditions.