Nighttime Orientation of Hatchling Green Turtles (Chelonia mydas) in Open Ocean

Abstract

Eleven hatchlings equipped with sonic transmitters and three equipped with chemical lights were tracked following their departure from beaches facing different points of the compass. The work was carried out off Bermuda with turtles hatched from eggs brought from Tortuguero, Costa Rica. Unless confronted with opposing shorelines, the turtles' travel paths which either approximated straight lines or took the form of gradual curves. These courses did not change to any great degree when land was below the horizon from turtle eye-level. The data suggest that hatchling C. mydas possess no inborn directional preference other than 'away from land'. The adaptive significance of this behavior may be that it serves to move the turtles rapidly beyond the reach of inshore predators.