An astonishing variety of animals can sense the Earth’s magnetic field—the list includes birds, salmon, frogs, sea turtles, honeybees, salamanders, lobsters, and rodents. You can add dolphins, too. According to new research by scientists in France, dolphins are apparently attracted to magnets, suggesting that they—along with some of their whale relatives—might have compasses in their heads.
Previous studies of the migration routes of free-ranging cetaceans, such as whales, dolphins, and porpoises, suggested they may be sensitive to magnetism. For instance, cetacean strandings seem to occur at weak spots in Earth’s magnetic field.
To find experimental evidence of this magnetism, researchers at the Université de Rennes in France investigated six bottlenose dolphins born in captivity that were kept at the French animal park Planète Sauvage in a delphinarium, an outdoor facility of four pools covering more than 21,500 square feet of water. They watched how the dolphins reacted to a plastic barrel containing either a strongly magnetized neodymium block or a demagnetized one that were otherwise identical in form and density.
The scientists found the dolphins approached the barrel about 30 seconds faster when it contained the strongly magnetized block than when it contained the demagnetized one. The researchers also dolphins possess magnetic crystals of magnetite in their brains.