Sharks have been swimming the oceans for hundreds of millions of years, yet for decades a simple question about them went unanswered: how do they find their way home over hundreds of miles of open water with no visible landmarks? According to a study published in the journal Current Biology, bonnethead sharks use Earth’s magnetic field as a built-in map. The study titled ‘Map-like use of Earth’s magnetic field in sharks,’ led by shark biologist Bryan Keller, provided strong evidence that sharks can sense magnetic cues well enough to navigate home from a distance.
Why smell was ruled out
Sharks cover vast distances during their travels. Some great whites are known to cross entire oceans, and lemon sharks make their way back to the same tiny Bahamian island year after year. Scientists used to think that smell was behind this navigation system until they realized that smell cannot cover such large distances, meaning smell is unlikely to explain how sharks navigate hundreds of miles back home. That left magnetism as the leading theory, as each point on Earth has a slightly different magnetic signature that animals could learn to read.
