Accuracy and precision of hatchling sea-finding orientation relative to dune proximity in three species of sea turtles

Abstract

\n Sea turtle hatchlings emerge from nests at night on sand beaches and immediately orient using visual cues. These cues involve horizon brightness, and on beaches without artificial lighting, hatchling orientation is seaward. Although many studies have examined which visual cues influence hatchling orientation, we found no work focused on a comparison of orientation among species. The purpose of the present study was to understand how dune proximity (distance from nest to dune silhouette) comparatively affected hatchling orientation in three sea turtle species sharing the same nesting beach. We measured accuracy and precision of hatchling orientation in hatchling loggerheads (Caretta caretta), green turtles (Chelonia mydas), and leatherbacks (Dermochelys coriacea), using tracks left in beach sand. Generalized linear models were used to test for effects from nest-dune distance in each species. We found that green turtle hatchlings had better orientation than loggerhead hatchlings. The results also showed that there was a significant decrease in hatchling orientation accuracy and precision in all species as the distance between nests and dune increased. We conclude that dune features are likely to provide important cues for hatchling orientation on sea turtle nesting beaches. Considering the importance of beach dunes to sea-finding success of hatchlings, we recommend management strategies to maintain natural beach profiles on sea turtle nesting beaches.