Meeting Abstract

64.6  Wednesday, Jan. 6  Geomagnetic Imprinting: The Key to Long-Distance Natal Homing in Sea Turtles and Salmon? LOHMANN, K. J.*; PUTMAN, N. F.; LOHMANN, C. M. F.; Univ. North Carolina at Chapel Hill; Univ. North Carolina at Chapel Hill; Univ. North Carolina at Chapel Hill KLohmann@email.unc.edu

Several marine animals, including salmon and sea turtles, disperse across vast expanses of ocean before returning as adults to their natal areas to reproduce. How animals accomplish such feats of natal homing has remained enigmatic. Salmon are known to use chemical cues to identify their home rivers at the end of spawning migrations, but such cues do not extend far enough into the ocean to guide migratory movements that begin in open-sea locations hundreds or thousands of kilometers away. Similarly, how sea turtles reach their nesting areas from distant sites is unknown. Both salmon and sea turtles detect the magnetic field of the Earth, and sea turtles are known to derive positional information from two magnetic elements (inclination angle and intensity) that vary predictably across the globe and endow different geographic areas with unique magnetic signatures. We propose that salmon and sea turtles imprint on the magnetic field of their natal areas and later use this information to direct natal homing. This hypothesis provides the first plausible explanation for how marine animals are able to navigate to natal areas from distant oceanic locations; it also appears to be compatible with present and recent rates of field change (secular variation). One implication, however, is that unusually rapid changes in the Earth’s field, as occasionally occur during geomagnetic polarity reversals, may affect ecological processes by disrupting natal homing, resulting in widespread colonization events and changes in population structure.