How tough are baby sea turtles? Scientists recently tested the endurance of hatchlings using mini treadmills and special swimsuits—all in the name of science.
But light pollution seems to disorient these tiny night crawlers, making them spend more time on land—and thus rendering them more vulnerable to threats. Instead of scooting to the sea within a few minutes, disoriented turtles can sometimes wander on land for hours. (See how artificial lights obstruct the night sky.)
So a pair of researchers from Florida Atlantic University decided to investigate if all this land crawling might tire out the confused hatchlings and make it harder for them to swim.
In one of the first studies of its kind, biologists Karen Pankaew and Sarah Milton reinforced the idea that sea turtles are hardy creatures. But they're still in danger: of the seven sea turtle species that swim our seas, all face potential threats, and two are critically endangered.
Crawling By the Numbers
Then, the researchers placed the turtles one at a time on a miniature treadmill they'd created in a laboratory, with an artificial light source at the front that attracted the animals in that direction.
Drawn to the glow, the hatchlings walked at a steady pace for 656 feet in one experiment and 1,640 feet in another, occasionally pausing to rest. The distances were chosen to simulate the how far the animals march on the beach.
Following the treadmill exercise, the scientists outfitted the turtles with specially designed swimming harnesses and lowered them into a water-filled tank. There, the hatchlings paddled while the scientists observed them for the next two hours. (See 13 graceful pictures of sea turtles.)
To gauge the turtles' level of exhaustion, the scientists measured oxygen levels in the air, as well as the animals' breathing rates, blood glucose levels, and plasma lactate production—indicators of energy exertion. The team also recorded the creatures' stroke rates in the tank.
The results surprised them: The long periods spent crawling didn't exhaust the turtles so much that they couldn't paddle in the water for the two-hour swimming period.
For an experimental control, the researchers also observed wild green and loggerhead turtle hatchlings on Florida's Boca Raton beach, which has turtle nesting grounds in both light-polluted and naturally dark areas.
Like the hatchlings in the lab, turtles in the light-polluted parts of the beach alternated between crawling and resting, increasing the amount of time on the beach. Non-disoriented turtles in naturally dark areas didn't rest at all, making a beeline directly for the ocean. (Related: "See Sea Turtles in the Wild.")
Ultimately, the lab turtles' long rest periods mean that in the wild, they'd spend more time on the beach—making them more susceptible to predators, dehydration, and other threats.
For the lucky ones that do make it to the surf, sea turtles still have to swim 30 miles offshore before they're pulled into the safety of the Gulf Stream, Godfrey notes. (See turtles come ashore in a mass-nesting event.)
A limitation of the study is it only analyzed the hatchlings' swimming abilities for a couple hours, he says, adding it provides valuable data for conservationists and government authorities to protect the threatened creatures.
"As conservationists, some of the most important tools that we have … are the tools of science and peer-reviewed studies," Godfrey says.
Milton says she was only permitted to test the turtles for the short period, but studying the reptiles swimming for a full 24 hours would be more informative.
And although the turtles weren't exhausted in the water, the study supports the theory that light pollution causes them to spend more time on land and opens them up to other threats, Milton adds.
"Even if the sea turtle hatchlings are not as exhausted," she says, "that increased time on the beach is still detrimental."
A previous version of this story misidentified the name of the current that sea turtles swim out to. This story has been updated.