Magnetic Navigation and Geomagnetic Imprinting in Sea Turtles and Salmon

Several marine animals, including sea turtles and salmon, migrate vast distances across seemingly featureless ocean before returning as adults to their area of origin to reproduce.  How animals accomplish such feats of natal homing has remained an enduring mystery.  Accumulating evidence, however, supports the hypothesis that such animals imprint on the magnetic field of their natal area and then use magnetic map information to guide themselves when they return years later.  Salmon appear to use magnetic information to navigate into the vicinity of the home river, close enough for chemical cues to allow completion of the spawning migration.  Similarly, sea turtles appear to exploit geomagnetic information to reach the natal area; moreover, magnetic cues may influence the selection of specific nesting sites on beaches.  In both groups of animals, subtle changes in the geomagnetic field are correlated with changes in natal homing behavior.  The ability to derive positional information from Earth’s magnetic field appears to be the centerpiece of long-distance natal homing in both sea turtles and salmon.  Similar navigational systems may be widespread among diverse ocean migrants.