Many animals have sensory abilities that human beings lack. Some fish, amphibians, birds, rodents, and even squids and octopuses are known to be able to sense Earth’s magnetic field. Sharks can sense the electrical voltages that exist in salty seawater.
Electricity and magnetism are closely linked, and researchers have long known that, as a side consequence of their electric sense, sharks can also sense magnetic fields. Sharks and their relatives are a major group of fish in the sea. Their habitats extend across thousands of miles of ocean, yet they return precisely to the same place year after year to feed, breed, and give birth.
The features of Earth’s magnetic field vary from place to place, like a kind of map. This led marine biologists to suspect that sharks might use their ability to sense magnetic fields to navigate, much as sea turtles were already known to do.
In 2021 a team of marine biologists from the United States published the first evidence that sharks really do use Earth’s magnetic field to guide their long-distance travels. The researchers captured bonnethead sharks off the coast of Florida, and brought them to a pool in their lab.
The pool was surrounded by electrical coils which could generate magnetic fields simulating Earth’s field. The researchers simulated the magnetic field at locations almost four hundred miles either north or south of the place where the sharks were captured. They found that the sharks oriented their swimming with respect to the fake magnetic cues in the direction that would have taken them back home. This was clear evidence that they use these same cues to navigate in the wild.
