| Summary: | Numerous animals embark on long-distance migrations, during which some of these animals can use the Earth’s magnetic field as a cue in orientation and navigation. Here, I study how loggerhead sea turtle hatchlings (Caretta caretta) use geomagnetic cues to guide themselves during their migration around the north Atlantic gyre, a current system that encircles the Sargasso Sea. My results suggest that hatchling turtles can use regional magnetic fields from numerous locations along the northern segment of their migratory pathway as open ocean guideposts. Exceptions may exist, however, in cases where regional fields have changed significantly in the recent past because of secular variation. My results also suggest that the magnetic field in which sea turtle eggs incubate influences the hatchlings’ subsequent ability to use regional fields for navigation. This finding has important implications for sea turtle conservation, as anthropogenic magnetic anomalies encountered by developing hatchlings at nesting beaches might disrupt their magnetic navigation abilities later in life.
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