Sea Turtle Hatchling Disorientation and Artificial Beachfront Lighting: A Review of the Problem and Potential Solutions

Raymond, Paul

INTRODUCTION: When reviewing the scientific literature on the ocean finding ability of hatchling sea turtles, one cannot help but be impressed by the abundance and quality of the research. The hatchling's emergence from the nest and journey down the beach to the sea, although completed in a matter of minutes under natural conditions, is perhaps the most intensely studied period in the animal's life history, with the possible exception of the nesting behavior of the adult female. One of the common conclusions of these studies is that light intensity, primarily on the horizon, is the main visual cue in the orientation of hatchlings. It also has been widely accepted that bright artificial lights along nesting beaches will disorient hatchlings, causing them to spend extended periods of time wandering landward or along the beach. Such disorientation usually results in an increase in mortality and a weakening of those hatchlings that eventually do reach the sea. Scientists are continuing to experiment on the specific details of the mechanisms of how hatchlings orient toward the sea. Reports of hatchling disorientation from artificial lights are increasing for all species of sea turtles as development increases on the world's nesting beaches. The purpose of this paper is to (1) summarize the scientific literature on the sea-finding ability of hatchlings; (2) review the documentation of hatchling disorientation caused by artificial lighting; (3) describe the types of light sources known to disorient hatchlings; and (4) propose ways in which these artificial lights can be reduced in number and modified so that they are not destructive to sea turtle hatchlings. I also discuss and evaluate past conservation measures taken in various coastal areas. I hope that this report will help encourage both the private and government sectors to implement beach lighting policies that are compatible with sea turtle conservation.