Sunday, April 12, 2015

Researchers Solve Young Sea Turtles' "Lost Years" Mystery

Kemp’s ridley sea turtles. Credit: Sea World
Juvenile sea turtles don’t just passively drift in ocean currents during their “lost years” as researchers once thought. Instead, turtles as young as 6-18 months of age are very active swimmers, according to a recent study conducted by NOAA and the University of Central Florida.  Researchers say that this revelation is an important new clue in the sea turtle “lost years” mystery of where exactly turtles travel in their first years of life before returning to coastal areas as adults to forage and reproduce.

Upon hatching, young sea turtles swim offshore and disperse with the help of ocean currents. The turtles are rarely observed by humans during the next two to ten years. Previous studies suggested that at least some juvenile turtles reside among mats of seaweed that provide shelter and habitat in the open sea. Not much was known about these juveniles’ movements during this time (which is why researchers dub it the “lost years”), but it had been widely assumed that turtles simply drift with ocean currents.

To solve this mystery, researchers placed specially designed solar-powered tags on 24 green & 20 Kemp’s ridley wild-caught sea turtle toddlers in the Gulf of Mexico. The tags were tracked by satellite for a short period of time before shedding cleanly from the turtle shells (a maximum of 2-3 months). Next to the turtles, researchers deployed small, carefully-weighted/passively-drifting surface buoys that were also tracked by satellite.

When the drifter tracks were compared to the sea turtles’ movements, the researchers found that the turtles’ paths differed significantly from the passive drifters. Using observed and modeled ocean current conditions, they found a difference of distance between the turtles and drifters to be as much as 125 miles within the first few days. In nearly every instance, the juvenile turtles’ swimming behavior appears to help them reach or remain in favorable ocean habitats.

"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,” said Dr. Kate Mansfield, director of the University of Central Florida’s Marine Turtle Research Group

“What is exciting is that this is the first study to release drifters with small, wild-caught yearling or neonate sea turtles in order to directly test the ‘passive drifter’ hypothesis in these young turtles. Our data show that one hypothesis doesn’t, and shouldn’t, fit all, and that even a small degree of swimming or active orientation can make a huge difference in the dispersal of these young animals.”

Image Credit: SeaWorld