Scientists Discover How Sharks Use the Earth’s Magnetic Field to Navigate Oceans
A new study found that sharks rely on the Earth’s electromagnetic field for navigation — just how a hiker relies on their compass while travelling.
Sharks are known to engage in “site fidelity,” which means they traverse long distances to reach the same spots year after year. How they manage to that — without the help of sophisticated navigation tools, of course — has baffled scientists for years. “How cool is it that a shark can swim 20,000 kilometers round trip in a three-dimensional ocean and get back to the same site? It really is mind-blowing. In a world where people use GPS to navigate almost everywhere, this ability is truly remarkable,” Bryan Keller, an oceanographer from Florida State University, who led the study, said in a statement.
But Keller and other scientists finally have an explanation for the sharks’ ‘remarkable’ abilities. Published in Current Biology last week, the study conducted a series of experiments that presented one answer: sharks rely on electromagnetic fields to navigate. “…they use the Earth’s magnetic field to help them find their way; it’s ‘nature’s GPS’,” Kellar notes.
Sharks have been known to be sensitive to electromagnetic fields for a while — leading scientists to suspect over the years that the cetaceans may be using the same for navigation. So, while the hypothesis for the present study wasn’t entirely new, this is the first time scientists were able to conclusively confirm their suspicions.
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The researchers captured bonnethead sharks from their habitats and exposed them to electromagnetic conditions mirroring those from hundreds of kilometers south of where they had been captured. Gathering positional data from the artificial magnetic fields, the sharks began swimming northwards — in the direction of home. And when they were exposed to magnetic fields aping those of their homes, they simply stay put.
“To orient towards home, these sharks must have some kind of a magnetic map sense — if I put you in the middle of nowhere you couldn’t point toward your house unless you knew where you were in relation to it, and that’s a map sense,” Keller explained.
Is the sharks’ ability to read and map magnetic fields entirely inherited, or do they simply learn it — piecing information together as they grow up swimming around? That’s what scientists are presently trying to understand. But the questions don’t end there — how sharks manage to sense electromagnetic fields is another question that has scientists intrigued, with some describing it as “a real mystery.” There are some speculations: ranging from electromagnetic fields invoking a protein in the retina of these marine animals, to sharks’ cells containing magnetic iron minerals enabling them to sense the field.