Sea Turtles Use Internal Magnetic Compass to Target Home Beaches

How do adult sea turtles find their way back to the beaches where they hatched? Scientists now have the answer. They've discovered that these turtles seek out unique magnetic signatures along the coast.

"Sea turtles migrate across thousands of miles of ocean before returning to nest on the same stretch of coastline where they hatched, but how they do this has mystified scientists for more than fifty years," said J. Roger Brothers, one of the researchers, in a news release. "Our results provide evidence that turtles imprint on the unique magnetic field of their natal beach as hatchlings and then use this information to return as adults."

Several years ago, the researchers proposed that animals, including sea turtles, might imprint on magnetic fields early in life. Yet this idea has been difficult to test. In order to get past this obstacle, the scientists studied changes in the behavior of nesting turtles over time. If turtles used the magnetic field, then naturally occurring changes in the Earth's field might influence where the turtles nested.

The researchers analyzed a 19-year database of loggerhead nesting along the eastern coast of Florida. In the end, they found a strong association between the spatial distribution of turtle nests and subtle shifts in the Earth's magnetic field.

In some places, the field shifted so that the magnetic signatures of adjacent locations along the beach moved closer together. This caused nesting turtles to pack themselves in along a shorter stretch of coastline.

The findings reveal that turtles just may rely on the Earth's magnetic field in order to find the beaches where they were born. Most likely, tiny magnetic particles in the turtles' brains respond to the Earth's field and provide the basis for the magnetic sense; that said, further studies will be needed in order to confirm this theory.

The findings are published in the journal Current Biology.

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