life sciences
T h e M a g n e tic M a p in S e a Sam Shutt
Dr. Catherine Lohmann, an animal behavior biologist at UNC-Chapel Hill, is fascinated with how sea turtles find their way home. Sea turtles travel hundreds, and even thousands of miles across the ocean. Yet they somehow manage to return to the precise location where they hatched. This could be attributed to sea turtles’ special sense known as the magnetic map.1 Sea turtles appear to utilize the Earth’s magnetic field to recognize specific geography. Indeed, the turtles can distinguish between different coastlines and find the exact area where they were born. Dr. Lohmann and her lab uncovered evidence that supports the theory that sea turtles geomagnetically imprint on the magnetic field of where they were born.2 Imprinting may allow sea turtles to recognize the magnetic field of their home. Dr. Lohmann’s research has contributed to scientific knowledge of long-distance marine animal migration and will have tangible applications in the near future. Dr. Lohmann began researching sea turtles in 1989. Over the years, she and her husband, Kenneth Lohmann, have created a lab that is at the forefront
of sea turtle and marine animal navigation research. Much of their collaboration occurs in Florida, where they study how loggerhead sea turtles Dr. Catherine Lohmann detect magnetic fields. In one important experiment, they collected young turtles along the coast and attached harnesses to them with computerized tracking systemts.3 They applied different magnetic fields to the newly hatched turtles in an outdoor water arena by using a surrounding metal coil. Then, they recorded turtle movement orientation using the tracking system. Dr. Lohmann found that turtles exposed to northern magnetic fields oriented themselves south and those exposed to southern magnetic fields oriented themselves north. The experiment clearly showed that sea turtle navigation is affected by the Earth’s magnetic field and that turtles seemed to use some kind of magnetic map (Figure 1). Sea turtles appear to use the map by responding to both the inclination angle
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