Sharks Use Magnetic Fields Like a Map, Study Finds

New research shows sharks navigate extraordinarily long trips using the Earth’s magnetic fields.

An overhead shot of bonnethead sharks in a holding tank. (Credit: Bryan Keller)

(CN) — Researchers have found new evidence showing that much like sea turtles, salmon and lobsters, sharks use magnetic fields to help guide them as they journey across the sea.

“It had been unresolved how sharks managed to successfully navigate during migration to targeted locations,” Bryan Keller of Florida State University Coastal and Marine Laboratory said in a statement.

Keller is the lead scientist and author of the study published Thursday in the journal Current Biology.

“This research supports the theory that they use the earth’s magnetic field to help them find their way; it’s nature’s GPS,” Keller added.

Researchers already knew that some species of sharks travel long distances every year to reach very specific locations and that sharks are sensitive to electromagnetic fields. From this knowledge, scientists speculated that sharks use magnetic fields to navigate, but they needed to find a way to test the theory.

“To be honest, I am surprised it worked,” Keller said in the statement. “The reason this question has been withstanding for 50 years is because sharks are difficult to study.”

Keller said he and his colleagues ran the study on bonnethead sharks because they return every year to an exact location, and because they realized smaller sharks would be easier to conduct studies on.

“The bonnethead returns to the same estuaries each year,” Keller said. “This demonstrates that the sharks know where ‘home’ is and can navigate back to it from a distant location.”

Keller and his team suspected the sharks relied on a magnetic map for help navigating their return trips. To test the theory, they conducted magnetic displacement experiments in holding tanks using 20 juvenile, wild-caught bonnetheads.

The sharks used for the experiment were exposed to magnetic conditions that represented locations hundreds of miles away from where they were caught, giving researchers a chance to predict how the sharks would orientate themselves in the case they were relying on magnetic cues.

The researchers predicted northward orientation in the southern magnetic field and southward orientation in the northern magnetic field would prove that sharks were taking positional information from the geomagnetic field as they attempted to compensate for their perceived displacement.

The sharks acted as researchers predicted when they were exposed to fields within their natural range.

The ability of sharks to navigate using magnetic fields may contribute to the population structure of sharks, researchers say, and will likely help explain the feats of other shark species, for instance a great white shark that was documented migrating between South Africa and Australia with the ability to return to the exact same location year after year.

“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?” Keller said in the statement. “It really is mind blowing. In a world where people use GPS to navigate almost everywhere, this ability is truly remarkable.

In an email, Keller praised the work of shark researchers who came before him.

“Our research is surely exciting, but we would not have been able to carry out our work without the groundwork laid by other researchers throughout the last five decades. This work was truly a collaborative effort, inclusive of those who are not co-authors. Specifically, James Anderson, Kyle Newton and Pete Klimley were all largely influential in assisting in the development of this work, through their own research efforts and direct discussions with me,” he wrote.

The work was supported by the Florida State University Coastal and Marine Laboratory and the Save Our Seas Foundation, which funds and supports research, education and conservation projects with a primary focus on endangered species of sharks, rays and skates, as well as their habitats.

Since its inception in 2003, the foundation has supported nearly 400 projects worldwide to protect the populations of sharks and rays whose presence is essential to the health and diversity of the seas, according to an emailed statement from foundation spokeswoman Aurélie Grospiron. Based in Switzerland, the Save Our Seas Foundation manages three permanent centers in South Africa, Seychelles, and the U.S.

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