From bacteria to butterflies, creatures have long relied upon the Earth's magnetic field to orient themselves and navigate the planet. Eels are another animal that possess this fascinating ability known as magnetoreception, but researchers have recently discovered that the sea slitherers use the talent in a unique way that lets them travel far with minimal energy.

What they found was that young European eels use magnetism to help guide them to the Atlantic Ocean's Gulf Stream. This lets them effectively use it as a conveyor belt that takes them from their birthing grounds in the Sargasso Sea to their coastal and freshwater habitats stretching from North Africa to Scandinavia. After living in those areas for a few years, the eels hop back on the Gulf Stream and hitch a ride back to the Sargasso Sea – a warm patch of ocean in the Atlantic rich in a type of free-floating seaweed called Sargassum – where they breed and die.

To come to their conclusion, Lewis Naisbett-Jones at the University of North Carolina, Chapel Hill along with Nathan Putman of the University of Miami and other colleagues, built a device that looks a bit like a wheel. Young eels, known as "glass eels" because of their transparent skin, are placed in the center chamber. Then, various magnetic fields are applied to the apparatus and the eels are free to move from the center chamber to any of 12 compartments around the wheel.

The researchers found that when a magnetic field was applied that mimicked one from the North Atlantic, the eels turned to face northeast, which is the direction they would need to travel from the Sargasso Sea to the Gulf Stream in order to be carried to their new homes. When the magnetic field mimicked that of the Sargasso Sea, however, the eels faced southwest, the direction that would carry them to the current and back to their breeding grounds.

Computer models were then used to confirm that even if the eels swam weakly in the directions they oriented under the magnetic stimulation, the majority would indeed hit the Gulf Stream and get where they needed to go.

"We were not surprised to find that eels have a magnetic map, but we were surprised to discover how well they can detect subtle differences in magnetic fields," says Lewis Naisbett-Jones at the University of North Carolina, Chapel Hill. "We were even more surprised when our ocean simulation models revealed that the little eels use their map not so much to locate Europe, but to target a big conveyor belt – the Gulf Stream – that will take them there. Presumably, a little bit of work (i.e., swimming) helps increase their chances of catching a mostly free ride to their destination."

The work has been published in the journal Current Biology.