Time-restricted orientation of green turtles

Sea turtles have an exceptional ability to travel accurately between known habitats as well as from unknown areas back to familiar habitats. Previous studies indicate that their ability to migrate long distances depends upon geomagnetic cues, but that they may rely on other undetermined cues once they are close to their destination. It has been suggested that they may then use visual cues for orientation during daylight hours, but detailed analysis of their movements when approaching their destination, particularly in relation to time of day, are lacking. This study examined the orientation behaviour of 22 displaced green turtles (Chelonia mydas), tracked en route back to their foraging habitats in eastern Australia. Study turtles tended to alternate stationary and travelling states during their trip home. Orientation corrections predominantly occurred immediately after a stationary state and after sunrise. This is the first study to demonstrate time-restricted orientation by sea turtles and provided a new insight into their sophisticated way-finding abilities.