Use of the earth's magnetic field by orienting cave salamanders (Eurycea lucifuga)

Abstract

Two groups ofEurycea lucifuga were trained to move bidirectionally within separate training corridors by alternately supplying moisture to limestone-filled compartments located at each end. Both corridors were aligned horizontally along the magnetic North-South axis of the earth. One corridor was enclosed within a cube coil which rotated the magnetic field horizontally 90° clockwise, so that the group contained in this corridor moved perpendicular to the North-South axis of the magnetic field. The other corridor was in the normal earth's field so that this second group moved parallel to the horizontal North-South component of the magnetic field. Testing involved releasing both groups in the center of a cross-shaped testing assembly made up of the two training corridors. The two groups were confined together in a release device for 60 min before release. In several tests the two groups were significantly oriented (P<0.05) along the appropriate trained axes with respect to the normal or altered magnetic field. Movements in these tests did not reflect a consistent response to any other potential source of orientation cues (P<0.001). It is concluded that cave salamanders are able to (1) perceive the earth's magnetic field and (2) exhibit a directional response with respect to a magnetic field which indicates a learned relationship to the environment.