A case of magnetic attraction: sea turtles use magnetic coordinates to navigate to their nesting sites

What do salmon, sea turtles and songbirds have in common? They are all excellent navigators capable of finding their way home after a long journey. These animals use a process called natal homing to make their way back to their birthplace to reproduce. Every two or three years, female sea turtles return to nest on the same beach where they first emerged as hatchlings. New research has shown that these turtles use the Earth’s magnetic field to guide them back home.

On a map of the world, you can pinpoint the exact location of any place using its unique latitude and longitude coordinates. Replace those latitude and longitude lines with intensity and inclination and you’ll have a new map of the world based on the Earth’s magnetic field. Inclination, the angle at which the magnetic field hits the Earth’s surface, and intensity are two important descriptors of the Earth’s magnetic field. Together, they can be used as a magnetic coordinate system, giving each place a unique magnetic signature.

Since the 1990s, biologists have known that sea turtles use the Earth’s magnetic field as a navigation system. One hypothesis in the field is that baby turtles imprint on the unique magnetic coordinates of their “home beach” as a way of guiding them back when they, themselves, are ready to nest. For the first time, researchers at the University of North Carolina, Chapel Hill have found evidence to support this idea of geomagnetic imprinting in sea turtles. Continue reading