Humans often find their way around by using a technology system called GPS. This system uses a device to calculate the position of individuals or things from any place on the ground or in the air. Now, scientists have found that some sharks may have a sort of natural GPS.
Scientists have known that other animals have a similar ability. Some animals can use Earth's magnetic fields to help them navigate. A magnetic field is an invisible area surrounding a magnet where you can observe magnetic forces. Earth's magnetic field extends out into space.
Animals such as birds and sea turtles use magnetic fields to find food and nesting sites. So, scientists wanted to know if bonnethead sharks — a type of small hammerhead shark — could use magnetic fields in the same way.
The scientists found that these sharks do in fact use magnetic fields to navigate thousands of miles across the oceans and find their way back home. In May 2021, the scientists published their study in a scientific journal.
Magnetic Fields
Bryan Keller studies marine policy, or laws affecting the ocean, at Florida State University. He worked on the study.
Keller and his team studied 20 bonnethead sharks. These sharks make migrations every year. A migration is the movement of a group of animals from one place to another. Bonnetheads live on both American coasts and migrate to the same spots every year to feed and give birth. The scientists wanted to know if magnetic fields played a role in helping them make these migrations.
In an experiment, the scientists caught bonnethead sharks off the coast of Florida. Next, they exposed the sharks to magnetic conditions. These conditions were similar to ones that the sharks usually encounter hundreds of kilometers away from the Florida location. The simulated conditions made the sharks think they were further south than they actually were. The sharks responded by swimming north, proving that they could respond to magnetic fields.
"We know that sharks can respond to magnetic fields," said Keller. "We didn't know that they detected it to use as an aid in navigation. You have sharks that can travel 20,000 kilometers (12,427 miles) and end up in the same spot."
According to Keller, bonnethead sharks likely are not the only kind of shark that can do this, and he said that great white sharks can also probably use the Earth's magnetic fields.
While the research provides evidence that sharks navigate the oceans using the Earth's magnetic fields, it doesn't explain exactly how they do it. Other experts say future studies could tell us more about it.
Navigating The Oceans
Robert Hueter is a scientist at the Mote Marine Laboratory & Aquarium in Florida. Hueter, who was not involved in the study, said he would like to see more research on how the sharks use magnetic fields to determine their location.
"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?" said Hueter. He said that Keller and his team made some progress at chipping away at this question.
The information learned from this study could also help scientists keep track of and manage different sharks throughout the world's oceans. It may help them understand why shark populations are declining. Another study published this year found that the worldwide abundance of oceanic sharks and rays, such as stingrays, dropped more than 70 percent between 1970 and 2018. Knowing how sharks navigate the seas could be one step toward saving them.
