The long-distance migrations of sea turtles involve some of the most extraordinary feats of orientation and navigation in the animal kingdom. Hatchling turtles entering the ocean for the first time immediately establish courses toward the open sea and steadfastly maintain them long after swimming beyond sight of land. As the turtles mature, they often follow complex migratory pathways that span entire ocean basins. Older turtles take up residence in feeding grounds but regularly migrate long distances to particular mating and nesting sites, after which many navigate back to the same feeding sites that they inhabited previously. How sea turtles guide themselves across vast expanses of seemingly featureless ocean has remained an enduring mystery of animal behavior. Growing evidence suggests that the Earth's magnetic field provides turtles with an important source of both directional and positional information that can be used in different ways at different times in their lives. As hatchlings, turtles may first use the Earth's field as a directional cue that enables them to maintain headings as they migrate out to sea. Later, in the open ocean, regional magnetic fields apparently function as navigational markers that elicit changes in swimming direction at crucial geographic boundaries, thus helping young turtles remain within favorable oceanic regions and progress along the migratory route. Turtles of this age, however, do not navigate to specific locations. In contrast, older juvenile turtles take up residence in coastal feeding grounds, and recent evidence indicates that they acquire a ?magnetic map? that enables them to navigate to specific feeding sites. A similar navigational ability may explain how adult turtles locate nesting beaches. The proposed research is designed to investigate the role that magnetic cues play in guiding the migrations of sea turtles. The researchers will investigate how young loggerheads exploit regional magnetic fields as open-sea navigational markers during their first transoceanic migration. In addition, the researchers will study the newly discovered magnetic map sense of juvenile turtles to gain insight into how turtles use magnetic fields to navigate to specific feeding sites and to determine how the map is organized. An improved understanding of how sea turtles guide themselves during transoceanic migrations, and learn to find specific geographic locations, will benefit conservation efforts to save these jeopardized species from extinction. In addition, the results of the work may provide insights into new methodologies relevant to human navigation. The project will provide research experience for a number of undergraduate and graduate students.
