Cooperative Fish and Wildlife Research Units Program: Florida
Education, Research and Technical Assistance for Managing Our Natural Resources

Hirama, S., B. Witherington, K. Kneifl, A. Sylvia, M. Wideroff, and R. R. Carthy. 2021. Environmental factors predicting the orientation of sea turtle hatchlings on a naturally lighted beach: A baseline for light-management goals. Journal of Experimental Marine Biology and Ecology 541 (2021) 151568.


On sea turtle nesting beaches, artificial lighting associated with human development interferes with hatchling orientation from nest to sea. Although hatchlingdisorientation has been documented for many beaches, data that managers can use in understanding, predicting, and managing the issue are of limited detail. Thepresent study provides baseline hatchling orientation data that can be compared to those from beaches with artificial lighting to prioritize light-management effortsthere. In 2014, the precision of hatchling orientation was quantified for 87 nests on a naturally lighted beach that had little to no artificial lighting. Precision ofhatchling orientation was regressed against seven environmental variables: beach slope, distance from nest to dune, dune height, apparent dune silhouette heightrelative to nest site, moon illumination percentage, cloud cover percentage, and relative humidity. Results favored a regression model that included distance fromnest to dune, with shorter distances from the dune predicting a narrower angular range (i.e., greater precision) of hatchling orientation. The study confirmed findingsof an earlier laboratory experiment that highlighted the importance to accurate hatchling orientation of a dark silhouette (dune) on the side of the nest site oppositethe ocean side. Reducing artificial light and promoting the planting of pioneer plants that assist dune formation can increase hatchling survival.