Sharks use the Earth's magnetic field as a means of navigation when crossing long distances in the oceans, scientists have found.
The researchers stated that their laboratory experiments with a species of small sharks confirmed long-standing speculations that sharks use magnetic fields as an aid in navigation, i.e. as a kind of natural GPS.
Such behavior has also been observed in other marine animals, such as sea turtles.
The study, the results of which were published this month in the journal "Current Biology" also answers the question of why sharks are able to travel long distances and find their way back to feed, reproduce and give birth, said one of the authors. Brian Keller.
"We know that sharks can react to magnetic fields. We didn't know that they noticed that they could use them as an aid in navigation. There are sharks that can travel 20.000 kilometers and end up in the same place," said Keller.
That question has intrigued researchers for years because sharks encounter few concrete landmarks like coral as they move through the ocean.
Looking for answers, Florida State University scientists decided to study hammerhead sharks, a species that lives on both American coasts and returns to the same estuaries every year.
The researchers exposed 20 of those sharks to magnetic conditions that simulated locations hundreds of kilometers away from where they were caught off Florida.
The scientists discovered that the sharks started swimming north when they deduced from magnetic signals that they were south of where they should be.
Scientist Robert Huter, who was not involved in the research, said the finding was compelling and added that further study is needed to determine how sharks use magnetic fields to determine their location and whether larger sharks that travel long distances use a similar system to find the right way.
The scientists say that the reliance on Earth's magnetic fields, discovered in hammerhead sharks, is likely to exist in other shark species, such as the great white that makes transoceanic journeys.
Keller says there's a very small chance that hammerhead sharks have developed a sensitivity to magnetic fields that other long-distance sharks haven't.
Keller adds that the research could help conservation efforts for the declining shark species.
This year's research showed that the number of sharks and rays in the oceans decreased by more than 70 percent from 1970 to 2018.
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