Sea Turtle Study Reveals The Mystery Behind Lost Juvenile Years
March 5, 2014

New Satellite Tracking Data On Sea Turtles’ Lost Years

Brett Smith for - Your Universe Online

After sea turtles hatch, they enter the sea and stay there for many years – returning later to coastal waters as large juveniles. This time period has been referred to as the "lost years" because not much has been known about what the relatively young turtles do and where they go.

In a study published on Tuesday in the journal Proceedings of the Royal Society B, a team of American research has used satellite tracking technology to finally reveal what sea turtles do as hatchlings.

"What is exciting is that we provide the first look at the early behavior and movements of young sea turtles in the wild," said study author Kate Mansfield, a biologist at the University of Central Florida. "Before this study, most of the scientific information about the early life history of sea turtles was inferred through genetics studies, opportunistic sightings offshore, or laboratory-based studies.”

“With real observations of turtles in their natural environment, we are able to examine and reevaluate existing hypotheses about the turtles' early life history,” Mansfield added. “This knowledge may help managers provide better protection for these threatened and endangered species."

To determine the turtles' movements, habitat preferences and how temperature affects them, the team followed 17 loggerheads for 27 to 220 days in the Atlantic Ocean using solar-powered satellite tags. The researchers found that while the turtles stayed in waters off the continental shelf, the turtles did not keep to the currents linked with the North Atlantic subtropical gyre, a massive circular ocean current that stretches from North America to Europe.

Prevailing theories have posited that loggerhead turtles from Florida's east coast perform a long, developmental migration in the North Atlantic subtropical gyre. However, the team found that the turtles may escape these currents into the center of the Atlantic or the Sargasso Sea.

The team also reported that sensors in the satellite tags showed the turtles' shells got much hotter than anticipated – causing the team to speculate that the turtles seek shelter in mid-ocean seaweed called Sargassum.

"We propose that young turtles remain at the sea surface to gain a thermal benefit," Mansfield said. "This makes sense because the turtles are cold blooded animals. By remaining at the sea surface, and by associating with Sargassum habitat, turtles gain a thermal refuge of sorts that may help enhance growth and feeding rates, among other physiological benefits."

While the researcher said they plan to pursue additional research on the habits of loggerhead turtles, they said the newly published study is an important first step in their efforts.

"From the time they leave our shores, we don't hear anything about them until they surface near the Canary Islands, which is like their primary school years," said study author Jeannette Wyneken, a professor of biology at Florida Atlantic University. "There's a whole lot that happens during the Atlantic crossing that we knew nothing about. Our work helps to redefine Atlantic loggerhead nursery grounds and early loggerhead habitat use."