ARI SHAPIRO, HOST:
Eels have always been mysterious animals. Aristotle thought they were born spontaneously from mud. Researchers do know that many eels found in places like Europe and North America are born in the same place - deep in the Atlantic Ocean. And scientists now say the elusive animals spread from that point using the Earth's magnetic field. NPR's Rae Ellen Bichell reports.
RAE ELLEN BICHELL, BYLINE: Baby eels make an epic journey from that spot in the ocean, sometimes traveling thousands of miles before finding their homes in rivers and lakes all over the place, from North America to North Africa to Scandinavia.
LEWIS NAISBETT-JONES: It's pretty crazy, yeah.
BICHELL: That's Lewis Naisbett-Jones, a marine biologist with the University of North Carolina, Chapel Hill, who studies the species commonly known as American and European eels. He wanted to know how those little eels do it. Other scientists had found that eels can somehow sense the Earth's magnetic field, which has a slightly different strength and direction at different points on the globe. Naisbett-Jones wondered if that was what guided the young animals on their trek. So he got a bunch of baby European eels.
NAISBETT-JONES: Around about a thousand (laughter) in the end.
BICHELL: They're each about the length of a pinky finger and delicate as noodles.
NAISBETT-JONES: And just small and transparent really is the best way to describe them, almost jelly-like.
BICHELL: Then he spent a summer putting those baby eels one by one into contraptions that he built to imitate the Earth's magnetic field at points along the journey. He'd drop an eel in, turn on a magnetic coil and let the eel decide which direction it wanted to swim in.
NAISBETT-JONES: And then recorded the directions that they moved in response to those magnetic fields.
BICHELL: As they wrote in the journal Current Biology, Naisbett-Jones and his colleagues found that the eels did respond to the magnetic fields, and they did so in a way that, had they been in the Atlantic Ocean, would have led them roughly to the Gulf Stream, a powerful current that could carry them to Europe.
NAISBETT-JONES: What we show here is that they're able to detect the magnetic field and use that to orient as a magnetic map.
BICHELL: If eels really do navigate this way, says Naisbett-Jones, then they'd join sea turtles, salmon and homing pigeons on a growing list of animals that can navigate using the planet's magnetism. The next research question, he says, is how about a decade after that first journey adult eels find their way all the way back to that same spot in the ocean to begin the cycle again. Rae Ellen Bichell, NPR News.
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