Researchers discovered adult sea turtles find their way back to the beaches where they hatched by seeking out unique magnetic signatures.
Past studies have found sea turtles use the Earth's magnetic signatures to navigate the ocean, but researchers have been unsure if they also use this technique to find their way back to their birthplace, the University of North Carolina at Chapel Hill reported.
"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 of the University of North Carolina at Chapel Hill. "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."
Researchers have suggested marine animals such as salmon and sea turtles imprint on magnetic fields very early in life, but this theory was unproven until the recent study.
"We reasoned that if turtles use the magnetic field to find their natal beaches, then naturally occurring changes in the Earth's field might influence where turtles nest," Brothers said.
To make their findings the researchers analyzed a 19-year database of loggerhead nesting along the eastern coast of Florida and identified a link between the spatial distribution of turtle nests and shifts in the Earth's magnetic field. When the Earth's field shifted so magnetic signatures of adjacent locations along the beach were closer together the nesting turtles tended to pack themselves onto shorter stretches of beach. Alternatively, in places where the magnetic signatures diverged the sea turtles tended to spread out.
It is important that nesting turtles return to their birth place because they require very specific environmental features such as soft sand and exact temperatures to hatch.
"The only way a female turtle can be sure that she is nesting in a place favorable for egg development is to nest on the same beach where she hatched," Brothers concluded. "The logic of sea turtles seems to be that 'if it worked for me, it should work for my offspring."
The findings were published in a recent edition of the journal Current Biology.
