Sea turtles have long mystified researchers by returning to beaches where they were hatched, magnetic signals may be the key, new research finds.

Loggerhead sea turtles ( Caretta caretta) are pretty loyal marine reptiles. Even with their roughly 8,000-mile-long migrations across oceans, they consistently return to the same feeding and nesting sites. Sea turtles can travel these distances by remembering the magnetic signatures of an area and storing that knowledge in a mental map.

Earth’s magnetic field is detected by species across the animal kingdom, but new research suggests that sea turtles may be using it in a different way.