Longdistance navigation in sea turtles

Adult sea turtles of several species migrate across vast expanses of ocean to arrive at specific nesting areas and feeding sites. Two hypotheses have been proposed to account for this remarkable navigation. The first is that chemical cues emanating from target areas guide turtles to their destinations. The second is that turtles can approximate their position relative to target regions using fea-tures of the earth’s magnetic field. Because animals often rely on multiple cues while migrating, the two hypotheses are not mutually exclusive. Satellite tracking experiments have revealed that migrating turtles often swim directly to distant goals, even when traveling perpendicularly to water cur-rents. Because animals usually change course frequently while seeking the source of a chemical plume, the consistency of headings casts doubt on the hypothesis that turtles follow such plumes over great distances. Chemical cues may nevertheless play a role in enabling turtles to recognize a target area in the final stages of a long migration. The magnetic navigation hypothesis is based on the finding that hatchlin