Scientists have discovered that sharks use Earth’s magnetic field as a kind of natural global positioning system (GPS) to travel long voyages across the world’s oceans.
Marine laboratory experiments with a small species of shark confirmed suspicions that sharks were using magnetic fields as a navigational aid.
This behavior has also been observed in other marine animals, including sea turtles.
The study, published in Current Biology, reveals why sharks are able to cross seas and find their way to feed, reproduce and give birth, according to marine policy scientist Brian Keeler, one of the study’s authors.
He said, “We know that sharks can respond to magnetic fields. We didn’t know that they discovered that to use it as a navigation aid … You have sharks that can travel 12,427 miles (20,000 km) and end up at the same point.”
Researchers have been fascinated by how sharks have been able to migrate over long distances for years.
Sharks go on their expeditions to the high seas, where they encounter few physical features, such as coral reefs, that can serve as landmarks.
In search of answers, scientists at Florida State University set out to study hammerhead sharks, a type of hammerhead shark that lives off the coast of the United States and returns to the same estuaries every year.
They exposed 20 cap heads to magnetic conditions that simulate locations hundreds of miles from where they were picked up in Florida.
The researchers found that the sharks began swimming north when the magnetic signals made them think they were located south of where they should be.
Robert Heter, a scientist emeritus from the Mote Marine Laboratory and Aquarium, who was not involved in the study, described the results as compelling.
But he said more study is needed to determine how sharks use magnetic fields to determine their location and whether large migratory sharks over long distances use a similar system to find their way.
He said, “The question has always been: Although sharks are sensitive to magnetic orientation, do they use this meaning to navigate the oceans and how? These authors have made progress in solving this problem.”
The researchers say the hood’s reliance on Earth’s magnetic field is likely shared by other species of sharks, such as white sharks, that make trips across the ocean.