Baby leatherback turtles 'struggle to see the sea'

·1-min read
Samantha Trail/Florida Atlantic University/Cover Images

Baby leatherback turtles struggle to find the sea when they leave their nests, unlike other turtles, researchers have found.

When sea turtle hatchlings emerge from their nests, usually at night, they crawl towards the ocean in what is known as "seafinding."

This means they have to discriminate between the brighter seaward versus a dimmer landward horizon and then move toward the source of the light.

That difference in radiance between horizons enables them to find the ocean. However, leatherback hatchlings often crawl around in circles trying to find the ocean.

Circling delays their entry into the ocean and places them in greater danger from predators like birds, crabs, and raccoons.

Researchers from Florida Atlantic University discovered that compared to their hard-shelled relative, the loggerhead, leatherbacks were 10 to 100 times less sensitive to light wavelengths than loggerheads.

"Leatherback eyes are less sensitive to all wavelengths of light than loggerheads, and during a dark night, they experience difficulty in determining the location of the seaward horizon," said Samantha Trail, first author and a Ph.D. student in the Department of Biological Sciences within the Charles E. Schmidt College of Science. "Even so, leatherback hatchlings eventually crawl to the sea, even during new moon. It just takes them longer because they stop occasionally to circle, which we think enables them to re-evaluate, and eventually confirm, the correct crawl direction."

Trail and her thesis advisor Dr Michael Salmon, second author and a research professor in FAU's Department of Biological Sciences, hypothesise that the costs of poor eyesight persist because other differences in leatherback visual capabilities enhance their ability to detect prey, mates or favourable habitats in the open ocean, where these turtles live.

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