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Journal of Experimental Biology, Vol 190, Issue 1 1-8, Copyright © 1994 by Company of Biologists

JOURNAL ARTICLES

ACQUISITION OF MAGNETIC DIRECTIONAL PREFERENCE IN HATCHLING LOGGERHEAD SEA TURTLES

K Lohmann and C Lohmann

During their natal migration, hatchling loggerhead sea turtles (Caretta caretta L.) establish courses towards the open ocean and maintain them after swimming beyond sight of land. Laboratory experiments have demonstrated that swimming hatchlings can orient using the earth's magnetic field. For the magnetic compass to function in guiding the offshore migration, however, hatchlings must inherit or acquire a magnetic directional preference that reliably leads them towards the open sea. On land, hatchlings find the ocean using light cues associated with the seaward horizon. To determine whether turtles might acquire a preference for a specific magnetic direction on the basis of such cues, we studied the magnetic orientation of turtles initially exposed to light from either magnetic east or west. Hatchlings that had been exposed to light in the east subsequently oriented eastward when tested in darkness, whereas those that had been exposed to light in the west swam westward. Reversing the magnetic field resulted in a corresponding shift in orientation, indicating that the turtles were orienting to the ambient magnetic field. These results demonstrate that light cues can set the preferred direction of magnetic orientation by loggerhead hatchlings. We therefore hypothesize that hatchlings initially establish a seaward course using visual cues available on or near land, then maintain the course using magnetic cues as they migrate into the open sea.


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W. P. Irwin and K. J. Lohmann
Magnet-induced disorientation in hatchling loggerhead sea turtles
J. Exp. Biol., February 1, 2003; 206(3): 497 - 501.
[Abstract] [Full Text] [PDF]

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K. J. Lohmann, S. D. Cain, S. A. Dodge, and C. M. F. Lohmann
Regional Magnetic Fields as Navigational Markers for Sea Turtles
Science, October 12, 2001; 294(5541): 364 - 366.
[Abstract] [Full Text] [PDF]


© The Company of Biologists Ltd 1994