Meeting Abstract

3.3  Jan. 4  Geomagnetic Navigational Markers for Hatchling Sea Turtles: Invisible Guideposts for a Transoceanic Migration FUXJAGER, M.J.*; LOHMANN, K.J.; Univ. of North Carolina, Chapel Hill; Univ. of North Carolina, Chapel Hill mattjf@email.unc.edu

Hatchling loggerhead sea turtles (Caretta caretta) from eastern Florida undergo long-distance migrations in the north Atlantic gyre, a current system that encircles the Sargasso Sea. Previous studies indicated that hatchlings exposed to regional magnetic fields that exist at crucial boundaries of the gyre (i.e., locations where turtles risk drifting off course) responded by swimming in directions that would, in each case, help turtles remain within the current system and advance along the migratory pathway. To investigate further the magnetic navigational system of loggerheads, we exposed hatchlings to several additional magnetic fields, including some that exist along the migratory route, one that exists in the center of the Sargasso Sea, and one that exists in a location north of the gyre where turtles are unlikely to go. When subjected to the fields along the migratory route, turtles responded by swimming in directions that appear likely to help them stay within the gyre current. In addition, turtles exposed to a magnetic field found in the Sargasso Sea were significantly oriented, with a mean angle toward the southwest. Turtles exposed to the field replicating one that lies north of the gyre oriented randomly. These results imply that the magnetic guidance system of hatchling loggerhead sea turtles is more complex than previously thought. Loggerhead hatchlings respond not only to fields that exist at critical boundaries of the gyre, but also to fields that exist elsewhere in the gyre and to fields that exist in at least some locations outside the main migratory pathway.