Disruption of the sea turtle magnetic map sense by a magnetic pulse.

Although some migratory animals can derive directional (compass) and positional (map) information from Earth's magnetic field, the underlying mechanisms of magnetic sensing have remained enigmatic. One hypothesis proposes that crystals of the mineral magnetite (Fe3O4) function in magnetoreception, a concept bolstered by findings that brief, strong magnetic pulses capable of reversing the magnetic dipole moment of magnetite affect magnetic orientation responses of several animals. Disentangling whether such pulses affected an animal's magnetic compass sense or magnetic map sense, however, has often been difficult. Here, we investigated the effect of a magnetic pulse on the magnetic map sense of loggerhead sea turtles (Caretta caretta) using an established conditioning assay that requires turtles to use magnetic map information but not their magnetic compass. We report that a magnetic pulse disrupted turtle responses, consistent with the interpretation that the magnetic map sense of turtles is based at least partly on magnetite-based magnetoreceptors.