Seafinding orientation of hatchlings exposed to filtered lighting: Effects of varying beach conditions

Under normal conditions, hatchling sea turtles crawl toward the ocean but streetlights placed on coastal roadways can attract the turtles toward land. Two light filters were designed to exclude the shorter light wavelengths most attractive to turtles. I did laboratory tests to determine if green turtle and loggerhead hatchlings oriented normally ("seaward") in the presence of filtered lighting. Light passed through either filter (#2422 acrylic and NLW) attracted the turtles unless coastal cues (an elevated horizon) were strong or background (full moon) illumination was present. Green turtles and loggerheads responded differently to the same filters, indicating that neither filter provided adequate protection for both species. I conclude that these filters fail to protect the turtles. Conventional forms of light control (shielding and/or lowering light fixtures, decreasing wattage, or turning off problem lights) remain the best way to shield turtles from the harmful effects of artificial lighting.