Sharks Use Earth's Magnetic Field as Compass to Travel 12,000 Miles Across Sea

Sharks have officially shown that they can circumnavigate the globe using Earth's magnetic fields.

Wired said scientists have been baffled for five decades as to how sharks travel 12,000 miles a year from South Africa to Australia and return to the same breeding grounds.

There are no street signs to guide them and no fixed landmarks to guide them for most of the journey. Currents and water levels are normally changing. The sun goes down at night and the stars fade away throughout the day. Yet the sharks continue to swim and charts a nearly perfect straight line through the ocean.

A recent report on juvenile bonnethead sharks discovered that the fish are sensitive to changes in the planet's magnetic field and use it as a means of navigation. Experts uploaded their paper, titled "Map-Like Use of Earth's Magnetic Field in Sharks," in the journal Current Biology.

What About Earth's Magnetic Field?

Experts have speculated for decades that sharks use the Earth's magnetic field as a kind of atlas. Still, it has been tricky to prove because sharks are notoriously difficult to research. It's challenging to keep them in captivity, and some species are gigantic. ABC News said the great white shark can grow to be 20 feet long and weigh over 2,000 pounds.

As a result, researchers led by Florida State University's Professor Bryan Keller studied twenty wild young bonnetheads trapped and became unwitting participants. They wanted to examine where the sharks would try and swim with the help of a magnetic field.

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Shark's Magnetic Navigation

It's challenging to scale up an experiment to the point that it can be studied in a controlled laboratory environment. A group of experts explains how they did it in their study. Keller designed an apparatus that could copy complex magnetic fields to test the long-held sharks' magnetic navigation theory. According to Bangkok Post, he constructed a 10-foot wooden cube with a large tank in the middle.

He then wrapped a mile of copper wire around the cube at predetermined intervals. When connected to electricity, the copper conducts an electrical current and generates a magnetic field. Keller may create a stronger or weaker field by adjusting the strength, simulating unique conditions that sharks could encounter in the ocean.

Navigating Sharks

If the sharks orientated themselves in a certain way based on the intensity and angle of the magnetic field, it would be evidence that they were using the knowledge to figure out where they were on the planet and which way to swim. Other species, such as sea turtles, have been studied using this method.

For the first time, researchers have witnessed how sharks used that capacity to infer location. Even so, there was a limit. Academic Times said the magnetic field of the cube was insufficient to track established navigators such as the great white. Keller explained that they needed a shark that was not too large but still migratory to research these species using this method.