US: We find our position (latitude and longitude) with a GPS system, but loggerhead turtles do it internally. American scientists have discovered that loggerhead turtles know their way around in the water by using the Earth’s magnetic field to determine both their exact latitude and longitude here on Earth.
The researchers already knew that turtles are able to tell the difference in latitudes (they are able to determine north and south directions). But, whether longitude is able to be determined by loggerheads, or any other animal for that matter, was not known by scientists — until now.
The Earth’s magnetic field is believed to be produced by convection currents in the outer part of the Earth’s core. These currents produce electric currents, which then produces the magnetic field. We can find the north magnetic pole, for instance, by using an externally made compass. Some animals have (natural) internal compasses that allow them to navigate themselves north and south.
The researchers’ study was published on February 24, 2011, in the journal Current Biology under the title “Longitude Perception and Bicoordinate Magnetic Maps in Sea Turtles.” It was authored by Nathan F. Putman, Courtney S. Endres, Catherine M. F. Lohmann, and Kenneth J. Lohmann, all from the Department of Biology at the University of North Carolina at Chapel Hill.
The researchers state in the abstract to their Current Biology paper, “The results demonstrate for the first time that longitude can be encoded into the magnetic positioning system of a migratory animal.” And, “Because turtles also assess north-south position magnetically, the findings imply that loggerheads have a navigational system that exploits the Earth’s magnetic field as a kind of bicoordinate magnetic map from which both longitudinal and latitudinal information can be extracted.”