The sea turtles' compass

Loggerhead turtles use the Earth's magnetic field as a compass. They memorize the patterns of the home beach when they were born, a new study in "Current Biology" says.

With help of their magnetic sense, sea turtles return back to their birth beach once they are about 12 years old. Even though their journey starts thousands of miles away, they perceive the intensity and angle of inclination of the Earth's magnetic field lines. These two factors vary regionally - different sections of coast have different magnetic patterns.

Also other animals have that sense for magnet fields: pigeons, migratory birds, crabs and even dogs or cows can perceive such patterns. Fascinating fact: Cows graze their pasture in a specific direction due to the magnetic field there.

But what if the magnetic field undergoes slight variation? Researchers at the University of North Carolina analyzed exactly that from 1993 to 2011 along Florida's coast. They found a correlation between the changes in magnetic field and distribution of sea turtle nests. Depending on fluctuation, nesting areas moved closer together, or other times were spread further apart.

The study did not imply that the turtles lay their eggs automatically in the exact spot where they were born. Many other factors - such as temperature, sand quality or accessibility of the beach - were also involved in choosing a nesting site, the researchers wrote.

The Earth's magnetic field originates from electrical currents in metal alloys in the Earth's core. We humans don't have that fine sense of being able to sense this magnetic field - yet we are certainly keen to understand it! The European Space Agency's Swarm mission in 2014 began delivering the highest-resolution-ever images of the Earth's magnetic field.