A LIGHT-INDEPENDENT MAGNETIC COMPASS IN THE LEATHERBACK SEA-TURTLE

Diverse animals can orient to the earth's magnetic field (1-6), but the mechanism or mechanisms underlying magnetic field detection have not been determined. Behavioral (7-9) and neurophysiological (10-12) results suggest that the transduction process underlying magnetic compass orientation in vertebrates is light-dependent, a finding consistent with theoretical models proposing that magnetoreception involves a modulation of the response of retinal photoreceptors to light (13, 14). We report, however, that leatherback sea turtle (Dermochelys coriacea) hatchlings orient to the geomagnetic field in complete darkness. Thus, light-dependence is not a universal feature of vertebrate magnetic compasses.