Earth’s magnetic field guides sea turtles home

Loggerhead sea turtles traverse entire oceans in search of jellyfish and other scrumptious food. But at nesting time, they always find their way back to the very same stretch of coast where they hatched.

Now scientists know how turtles accomplish the feat: They recognize their home turf using Earth’s magnetic field, which varies across the globe.

Although long suspected, this hypothesis had been challenging to test. J. Roger Brothers and Kenneth Lohmann of the University of North Carolina at Chapel Hill realized that if turtles homed in on beaches’ unique magnetic signatures, their nests should migrate in response to subtle natural changes in the geomagnetic field. Over 19 years, the scientists found that the nests of sea turtles in Florida clustered more densely in places where magnetic signatures got closer together and spread out where signatures drifted apart, the researchers report January 15 in Current Biology.