Sea Turtle Hatchling Strategies for Navigation
Sea turtles’ eggs are laid at night to minimize the likelihood of their discovery by predators, and the offspring, when ready to emerge from their eggshells and dig their way out of the sand, hatch at night for the same reason. Since the offspring are especially vulnerable immediately after hatching, it is vital for them to get to the sea as soon as possible. Turtle hatchlings use a number of cues to tell them where the sea is.
The most important cue seems to be light. The night sky is usually brightest over the sea. Cover a turtle hatchling’s eyes, and it cannot find the sea even if there is other information available, such as a downward slope of the sand toward the water’s
edge. The hatchlings respond to light cues covering a vertical range of only about 30˚ above the horizon or, depending on the species, even less. Responding only to lights that are close to the horizon decreases the risk that hatchlings will become confused. They seem less attracted to yellow light than to other colors — loggerhead turtles show an aversion to yellow light — and this preference may keep them from becoming disoriented by the rising Sun.
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