New research suggests that dolphins can add magnetic sense to their already-impressive resume of abilities.
When researchers presented the brainy cetaceans with magnetized or unmagnetized objects, the dolphins swam more quickly toward the magnets, the new study found. The animals may use their magnetic sense to navigate based on Earth's magnetic field, the researchers said.
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"Inside the ocean, the magnetic field would be a very good cue to navigate," Kremers told LiveScience. "It seems quite plausible for dolphins to have a magnetic sense."
Kremers and her colleagues tested the magnetic sense of six bottlenose dolphins at the delphinarium of Planète Sauvage in France. The researchers presented the animals with barrels containing either a magnetized neodymium block or a demagnetized block of identical shape and density. Then the researchers video recorded the animals poking around the barrels.
When the barrel contained the magnetized block, the dolphins swam toward it much faster than when it contained the demagnetized block, Kremers and her colleagues observed. They pointed out that the dolphins could not tell the blocks apart simply by using echolocation or bouncing sound waves off them.
If dolphins do perceive magnetic fields, it's not yet clear how they do it, Kremers said. Scientists have proposed that animals with a magnetic sense have tiny "ferromagnetic" particles (such as magnetite) in their body cells that react with the magnetic field and signal the nervous system. The researchers noted that magnetite has been found in the brain membranes of dolphins, but that doesn't prove that the animals use it to sense magnetic fields.
They said more studies will be needed to determine whether the dolphins can actually detect and follow Earth's magnetic field.