Sea turtles use geomagnetic signatures to return to nesting sites near where they were born.

Credit: J. Roger Brothers

These animals navigate across oceans using Earth's magnetic field, but it has been unclear how they find the same coastal nesting sites as their mothers. Roger Brothers and Kenneth Lohmann at the University of North Carolina in Chapel Hill studied loggerhead sea turtles (Caretta caretta; pictured) in Florida.

They found that the location of the animals' nests each season was associated with changes in the strength and direction of Earth's magnetic field at each site. In areas where the same magnetic signature spreads out over time, nests were made farther apart. When the signature shrank, the nests were closer together.

Similar mechanisms could be at work in other animals that migrate back to their birthplaces, the authors suggest.

Curr. Biol. http://doi.org/zc7 (2015)