EVIDENCE FOR THE INDEPENDENT EVOLUTION OF VISUAL PERCEPTION DURING SEAFINDING BY HATCHLING LEATHERBACK SEA TURTLES (DERMOCHELYS CORIACEA)

Hatchling marine turtles exhibit a positive phototaxis by crawling toward the lowest and brightest horizon when they emerge from nests on the beach at night, which should lead them to the ocean (“seafinding”). Previous research with cheloniid (loggerhead and green turtle) hatchlings demonstrated that the perceptual spectral sensitivities are well below the light available on the beach regardless of lunar phase. The goal of this research was to determine the perceptual spectral sensitivities of leatherback hatchlings, the most distantly related of all extant sea turtle species. This study revealed that, like cheloniids, leatherbacks are most sensitive to shorter wavelengths (< 500 nm). However, leatherbacks were 10 – 100x less sensitive than cheloniids at all tested wavelengths. This difference in sensitivity corresponds with increased crawl duration and circling behavior under new moon conditions when light levels are lowest and the difference in radiance between the landward and seaward direction is small.