Sea Turtles Guided By Magnetic Field

Sea turtles, those crusty old mariners that ply the oceans, may, like their human counterparts, use a kind of global positioning system to perform their navigational feats, scientists say. But unlike humans, who rely on signals beamed from satellites, turtles appear to sense the earth’s magnetic field.

A husband-wife team of biologists at the University of North Carolina at Chapel Hill, Dr. Kenneth J. Lohmann and Dr. Catherine M.F. Lohmann, have conducted experiments on just-hatched loggerhead turtles, showing that they can detect magnetic fields of different strengths.

Coupled with their earlier research demonstrating that loggerheads can discern inclination, the angle that magnetic field lines make with respect to the earth’s surface, the new data suggest that the reptiles “may have a global position-finding sense,” Kenneth Lohmann said.

In most parts of the oceans where sea turtles travel, magnetic field intensity and inclination angle vary in different directions, forming a grid that is roughly analogous to longitude and latitude.

Any point in these regions can be determined by a unique combination of intensity and inclination angle.