New study sheds light on sharks' navigation
In this file photo taken on April 26, 2012 a Bonnethead shark swims at the Aquarium of the Pacific in Long Beach, California.
Sharks use the Earth’s magnetic field as a sort of natural GPS to navigate journeys that take them great distances across the world’s oceans, scientists have found.
Researchers said their marine laboratory experiments with a small species of shark confirm long-held speculation that sharks use magnetic fields as aids to navigation — behavior observed in other marine animals such as sea turtles.
Their study, published this month in the journal Current Biology, also sheds light on why sharks are able to traverse seas and find their way back to feed, breed and give birth, said marine policy specialist Bryan Keller, one of the study authors.
“We know that sharks can respond to magnetic fields,” Keller said. “We didn’t know that they detected it to use as an aid in navigation ... You have sharks that can travel 20,000 kilometers and end up in the same spot.”
The question of how sharks travel long distance has long intrigued researchers.
They undertake their journeys in the open ocean where they encounter few physical features such as corals that could serve as landmarks.
Looking for answers, Florida State University scientists decided to study bonnethead sharks — a hammerhead that lives on both American coasts and returns to the same estuaries every year.
Researchers exposed 20 bonnetheads to magnetic conditions that simulated locations hundreds of kilometers away from where they were caught off Florida.
They found that the sharks began to swim north when the magnetic cues made them think they were south of where they should be.
That finding is compelling, said Robert Hueter, senior scientist emeritus at Mote Marine Laboratory & Aquarium, who was not involved in the study. Hueter said further study is needed to find how the sharks use the magnetic fields to determine their location and whether larger, long-distance migrating sharks use a similar system to find their way.
“The question has always been: Even if sharks are sensitive to magnetic orientation, do they use this sense to navigate in the oceans, and how? These authors have made some progress at chipping away at this question.”
