Many marine animals have some way of swimming back toward the spot they were born when it comes time to give live to their own offspring. Scientists have figured out that salmon use the lines sketched by the Earth’s magnetic field and that sea turtles read magnetic signatures to navigate both north-south and east-west in the open ocean. (The second positioning is a trickier feat that took humans centuries to figure out.)

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Now researchers know that magnetic sense also helps turtles find their home beach. "Each part of the coastline has its own magnetic signature, which the animals remember and later use as an internal compass," writes Carrie Arnold for National Geographic.

The team poured through records of 19 years of loggerhead sea turtle nesting in Florida, reports Laura Geggel for Livescience.com. Since the Earth’s magnetic field bends and twists across the surface over time as molten metal "sloshes around" the Earth’s core, the researchers thought that the turtles might sense those changes. Indeed, the found fewer nests in places where the field had shifted farther apart and more nests in places were signatures from nearby beaches had converged. The study was published in Current Biology.

"It's pretty fascinating how these creatures can find their way through this vast expanse of nothing," one of the study authors, J. Roger Brothers, a graduate student at the University of North Carolina, Chapel Hill, told National Geographic. Knowing more about how turtles find their way home could help conservationists predict their movements and better protect the endangered reptiles, he says.