It has been a mystery that how the loggerhead sea turtles migrate several miles in the open ocean, where there are no visual landmarks. But, now researchers seem to have solved this mystery.

Loggerhead turtles navigate their way in the ocean by picking up magnetic cues from the Earth's surface, according to a new research published in Current Biology.

Though several species, including sea turtles, were known to rely on magnetic cues to determine latitude, but it had been believed that those signals had been considered unpromising for determining east-west position (i.e. longitude).

The most difficult part of open-sea navigation is determining longitude or east-west position. It took human navigators centuries to figure out how to determine longitude on their long-distance voyages, said Nathan Putman, lead author of the study, in a statement. This study shows, for the first time, how an animal does this.

The latest findings show that the loggerhead turtles use both the inclination of magnetic field to the Earth as well as the strength of the magnetic field for migrating thousands of miles in the ocean.

Researchers say that near the Equator, the field lines are about parallel to the Earth's surface. As one travels north from the Equator, the field lines grow progressively steeper until they reach the poles, where they are directed straight down into the Earth.

The magnetic field also varies in intensity, being generally strongest near the poles and weakest near the equator. Both parameters appear to vary more reliably from north to south than east to west, leading many researchers to conclude that the magnetic field was useful only for latitudinal information.

Although it is true that an animal capable of detecting only inclination or only intensity would have a hard time determining longitude, loggerhead sea turtles detect both magnetic parameters, Putman said. This means that they can extract more information from the Earth's field than is initially apparent.

This work not only solves a long-standing mystery of animal behavior but may also be useful in sea turtle conservation, Kenneth Lohmann of the University of North Carolina said. Understanding the sensory cues that turtles rely on to guide their migrations is an important part of safeguarding their environment.

The recent findings may not only have important implications for the turtles, but could also lead to new approaches in the development of navigational technologies, the researchers say.