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Dolphins Can Detect Magnetic Fields with Their Dolphin Supersenses

Is it how they navigate, or something more sinister?

As if dolphins needed another advantage. A study just published in the journal Naturwissenschaften—The Science of Nature contends that our intelligent sea-going friends are magnetoreceptive. That is, they can perceive when something is magnetized.

One of an infinite number of sixth senses that we human beings lack is magnetic sensitivity. Deer and cattle graze on a north-south axis, and migrating birds, turtles, and fish all rely on Earth's magnetic poles to navigate. Dogs, for reasons unknown, seem to orient themselves to Earth's magnetic north when they poop.

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And now dolphins can be counted among the ranks of the ocean-faring magnetoreceptive, along with sharks, stingrays, and, for some reason, lobsters.

Dolphins are able to discriminate between objects based on their magnetic properties

This isn't completely out-of-the-blue; it had already been suspected that dolphins and long-distance migrating whales might be sensitive to the Earth's magnetic fields. This has been inferred from the routes they take, where they seem to strand themselves, and the as-yet-unexplained tendency of captive bottlenose dolphins in the Northern Hemisphere to swim predominantly in a counter-clockwise direction, and dolphins in the Southern Hemisphere to swim predominantly in a clockwise direction.

The team of French researchers behind the current study didn't fully answer the geomagnetic orientation question, but they did find evidence that dolphins are attracted to magnetic fields.

Barrels with both magnetized and demagnetized neodymium blocks were lowered into pools, where six captive-born bottlenose dolphins could interact with them. Neither the person lowering the barrel into the water, nor the one watching the video of the encounter knew whether or not the barrel's payload was magnetic. But it seems the dolphins did.

Image: Jay Ebberly/Flickr

The dolphins were seen approaching the magnetic barrels much faster than they approached the nonmagnetic ones. Once there, they interacted with the barrel in pretty much the same way regardless of magnetism. So, the study suggests that it's possible the dolphins were "more intrigued than physically drawn" to the magnet. In any case, it does open the possibility of geomagnetic navigation.

"Dolphins are able to discriminate between objects based on their magnetic properties, which is a prerequisite for magnetoreception-based navigation," said Dorothee Kremers, lead author of the study, in a statement. "Our results provide new, experimentally obtained evidence that cetaceans have a magnetic sense, and should therefore be added to the list of magnetosensitive species."

It sure seems like dolphins are up to something odd, at least. Not only are they harassing porpoises off America's western coast, but a thousand dolphins have gathered in some sort of "superpod" in the Bristol Channel, according to a BBC report. Should we need to appease them, or at least distract them—hey, who knows what thousands of dolphins could be plotting—a few magnets could do the trick.