Magnetoreception, or the ability of living organisms to perceive magnetic fields, has piqued the interest of many scientists over the last forty years. Since its discovery, dozens of different species have been identified which have the ability to sense direction and navigate using the Earth’s magnetic field. Sea turtles, honeybees, spiny lobsters and migratory birds all possess a built-in magnetic compass that allows them to perceive and utilize information from the magnetic field. Furthermore, it’s also evident that our planet’s magnetism can even act as a map for some species.
Various observations, such the migration routes of free-ranging cetaceans (whales, dolphins and porpoises), have led scientists to believe that these animals may also be sensitive to the geomagnetic field. Experimental evidence to back up these assumptions, however, has been lacking.
To investigate this further, a team of researchers from the Université de Rennes set out to examine the behavior of six captive bottlenose dolphins kept at Planète Sauvage safari park, France. The scientists recorded the response of the dolphins to the presentation of two devices contained within a barrel: a strongly magnetized block or a demagnetized control. The blocks were identical in shape and density and therefore indistinguishable by echolocation, which is a form of biological sonar used by various animals to locate and identify objects.
During the experiments, the dolphins were free to swim throughout the pools as they pleased. To remove bias, the experimenter that added the block to the barrel was blinded, meaning that they did not know which block was which, as were the researchers that examined the video recordings.
They found that the dolphins were much quicker to approach the barrel when it contained the magnetized block when compared with the control block. However, they also found that they did not interact differently with the two barrels. According to the team, this could suggest that the dolphins were more intrigued, rather than physically drawn, to the barrel with the magnetized block inside.
“Dolphins are able to discriminate between objects based on their magnetic properties, which is a prerequisite for magnetoreception-based navigation,” lead author of the recently published Naturwissenschaften study Dorothee Kremers said in a news-release. “Our results provide new, experimentally obtained evidence that cetaceans have a magnetic sense, and should therefore be added to the list of magnetosensitive species.”