Near-ultraviolet radiation guides the emerged hatchlings of loggerhead turtles Caretta caretta (Linnaeus) from a nesting beach to the sea at night

Hatchling sea turtles (Caretta caretta) emerge from their beach nests at night and crawl seaward immediately, even where the sea is not visible to them. This sea-finding ability of hatchlings is one of the outstanding phenomena of animal orientation. The primary sea-finding mechanism is an orientation towards light, and blindfolded hatchlings could not find the sea. Hatchlings of loggerhead turtles avoid yellow and orange light and are strongly attracted to light in the near-ultraviolet to green part of the spectrum. Here we demonstrate in experiments at a nesting beach that (1) loggerhead hatchlings orient to near-ultraviolet radiation, and (2) the intensity of near-ultraviolet radiation is always higher seaward than landward on all nights. These results are consistent with long-term monitoring data that show emergence of loggerhead hatchlings takes place during any phase and position of the moon. To prevent mis-orientation of hatchlings, roads, and human settlements fronting turtle nesting beaches should use lights that do not emit near-ultraviolet radiation.