Records of compass heading for long-distance ocean migrators show mid-ocean reorientation

The mechanisms by which animals navigate during long ocean migrations to specific targets remain equivocal despite over a century of investigation. To address this question, we developed and deployed a new tag that allowed the compass heading of migrators to be remotely relayed via satellite. On transocean migrations (>1000 kilometers and mean duration 27.5 days) between nesting and foraging sites, green turtles ( Chelonia mydas ) tended to perform sections of travel with a consistent compass heading, even if that led them off course, before reorienting. That migrating turtles did not continuously fine-tune their heading but rather made occasional reorientations is consistent with the suggestion that they use geomagnetic signposts, or other crude maps, to facilitate occasional course corrections.