Lohmann, K., IBN 94-19993 Mechanisms of Orientation and Navigation Sea turtle hatchlings begin an amazing long-distance migration as soon as they emerge from their underground nests on oceanic beaches. They scramble to the sea and swim through the surf, then quickly establish a course towards the open ocean, Maintaining their direction after swimming beyond sight of land.. Little is known about how hatchling sea turtles maintain their course through a vast ocean that contains no obvious landmarks. Near the beach, wave direction provides a reliable cue, Which the hatchlings seem to use initially. But farther from land, where waves no longer reliably indicate direction, the hatchlings appear to depend on the magnetic field of the earth. Recent experiments have demonstrated that sea turtles have a well- developed magnetic compass that allows them to maintain a specific heading, even in total darkness. For long-distance migrants such as sea turtles, the geomagnetic field not only provides a possible cue for compass orientation, but a potential source for worldwide positional information. Several parameters of the earth s magnetic field vary predictably with latitude and it appears that hatchling sea turtles can sense these parameters. The research that Dr. Lohmann will carry out is designed to investigate: (1) how hatchlings may use these geomagnetic parameters in global position finding; (2) how young sea turtles may acquire a directional preference and how the preference influences orientation; and (3) the mechanism hatchlings use to detect wave direction and how this information interacts with the information from the magnetic compass. All species of sea turtles are now either threatened or endangered. Thus this research will provide information useful to conservation workers trying to save these animals from extinction. In addition it will provide valuable information about how animals (including turtles, fis h and whales) navigate using information from the magnetic field of the earth. .
