Scientists have always had a hunch that sharks can swim across oceans because of their ability to use the Earth’s magnetic field. They can swim in perfectly straight lines without using any stable landmarks on top of water temperature changes, currents, and night/day time.
The problem with all of this is scientists always had a theory this is how sharks worked but were never able to prove it. It is very hard to study sharks because they aren’t able to be put in captivity, especially when you get to the 2,000+ pound great whites. Bryan Keller from Florida State University Coastal and Marine Laboratory made a breakthrough and the findings were published in Current Biology.
In a WIRED article, they went into detail on how their experiment worked: “[they] have to build an apparatus that could mimic specific magnetic fields. He constructed a 10-foot wooden cube with a large tank at the center. Then he coiled over a mile of copper wiring around the cube at precise intervals. […] By adjusting the power, Keller could create a stronger or weaker field, mimicking specific conditions the sharks might encounter in the ocean. If the sharks oriented themselves in a certain way based on the strength and angle of the magnetic field, that would be an indication that they were using that information to understand their position on the planet and to figure out which direction to swim.”
The types of sharks Keller experimented with were 20 juvenile bonnetheads. These sharks are under 2 feet long and migrate thousands of miles annually. They go to waters in Florida in the summer and the Gulf of Mexico during the winter.
Keller experimented with three artificially created magnetic fields. Knowing their swimming patterns, he mimicked a magnetic field they’d get in Florida, one 600 kilometers south along their normal route and another was 600 kilometers north (where they normally don’t go). After seeing how the sharks reacted from these artificial magnetic fields, Keller was able to conclude that they use this info to travel.
These conclusions were a clear indication that sharks are using Earth’s magnetic fields as a map. After traveling thousands of miles from point A to B, this info they gather helps them return home.
Keller’s breakthrough is huge in the biology field and understanding the shark’s migration patterns is a huge first step to learning more about them!