If the magnetic compass functions in the offshore migration of hatchlings, then turtles must inherit or acquire a preference for swimming toward the magnetic direction that coincides with the seaward direction. In initial experiments investigating the magnetic compass, hatchling loggerheads were permitted to swim toward a dim light in the east (their normal migratory direction) before they were tested in darkness. These animals subsequently swam east to northeast in the geomagnetic field. To determine whether the initial course of the turtles influenced their subsequent magnetic orientation, turtles in one experiment were exposed to light from either magnetic east or west before being tested in darkness (Lohmann and Lohmann, 1994). Hatchlings that had been exposed to light in the east subsequently oriented eastward, whereas those that had been exposed to light in the west swam approximately westward. Reversing the magnetic field resulted in......Read on.....http://www.unc.edu/depts/oceanweb/turtles/

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