Where do sea turtles spend their 'lost years?'

Researchers tracked young sea turtles as they began their decade-long disappearance into the open-ocean.

Like Shakespeare and Merlin, young sea turtles also have their “lost years.”

At the age of 1, “yearling” turtles head for the open ocean, essentially disappearing for an entire decade. But with solar-powered tracking devices, researchers were able to follow 44 wild turtles on their deep-sea rumspringa. Their findings, which were published Thursday in Current Biology, surprised them – contrary to common assumption, young sea turtles aren’t drifters after all.

With little data to work from, scientists previously guessed that young sea turtles spent their lost years living the easy life – passively drifting on ocean currents. Katherine Mansfield, lead author and head of the turtle research group at the University of Central Florida, sought to test this “passive migration” hypothesis. To do so, she needed young sea turtles between the ages of six months and two years. Unsurprisingly, turtles in their lost years were tough to find – Dr. Mansfield and her team would sometimes cover 60 miles without finding a single turtle.

After a grueling collection process, Mansfield and co-author Nathan Putman were finally able to secure a sample size large enough. In all, they tagged 20 Kemp’s ridley turtles and 24 green turtles. Each was fitted with a solar-powered tracking device and released alongside a control – a floating buoy. The buoys, which represented “drifters,” were also tagged and tracked.

When the data came back, it contradicted previous assumptions about young turtle migration. The turtles weren’t merely drifting – they were actively swimming. At a slow, but persistent rate of a few centimeters per second, the yearlings changed course and swam away from the drifting bouys. And what’s more, they were surprisingly self-directed.

"The green turtles, for instance, were really set on going east a lot of the time,” Dr. Putman told the BBC. “And the Kemp's ridley turtles, over large portions of the tracked area... were very convinced that they should be swimming north."

There’s still much to learn about the behavior of these animals – satellite tracking devices are too large for tiny hatchling turtles, leaving a notable gap in data. But in the meantime, Mansfield and Putman say their research can provide an immediate benefit to sea turtles and those who study them.

"The results of our study have huge implications for better understanding early sea turtle survival and behavior, which may ultimately lead to new and innovative ways to further protect these imperiled animals,” Mansfield said in a press release.