Turtle Hatchings Sometimes Crawl the Wrong Way, But They’re Hardy

Turtle hatchlings head for the sea.

HATCHING IN DARKNESS ON SANDY BEACHES, new little turtles instinctively crawl toward the light. In a natural setting, this is good – the horizon over the sea is always brighter than the darkness of the land side, drawing them to the ocean, where they belong.

But the light from the back porch light of a beachfront home, the signage of a seaside resort or skyglow from urban areas near beaches can cause them to crawl the wrong way. This is bad.

THE GOOD NEWS IS THAT TURTLE HATCHINGS HAVE EXCELLENT ENDURANCE. Once they reach the water, they swim just as strongly as hatchings that went the right way from the start, according to a study by scientists at Florida Atlantic University.

How do they know? They put them on a treadmill.

“As a result of these rest periods, the extended crawl distances had little effect on oxygen consumption, blood glucose, or plasma lactate levels. Swim performance over 2h following the crawls also changed little compared to controls,” say FAU biologist Sarah L. Milton and graduate student Karen Pankaew in their report in the Journal of Experimental Biology.

THE GREEN AND LOGGERHEAD HATCHLINGS tested on the treadmill (actually an adapted belt sander) and on a Boca Raton beach over distances of 200 and 500 meters rested a lot – 8 to 12 percent of the time for green turtle hatchlings and 22 to 25 percent for loggerhead hatchlings, they said. Observations of them then swimming in a tank for two hours following their journeys showed little change compared to the hatchlings in control populations.

The biggest threats hatchings face during extended crawls are from predators like birds and foxes, they said.

A New York Times story on the research by science writer James Gorman features an interview with Dr. Milton and a video on their project, treadmill and all.

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