According to a new study published in the journal Current Biology, young sea turtles don’t just passively drift in ocean currents during a period known as the ‘lost years’ as scientists once thought.
The green turtle (Chelonia mydas). Image credit: Brocken Inaglory / CC BY-SA 3.0.
Upon hatching, young turtles migrate offshore and are rarely observed during the next 2-10 years, the so-called ‘lost years,’ until they return to coastal waters as larger juveniles.
Not much is known about these turtles’ movements during this period, but it has been widely assumed that they simply drift with ocean currents.
The authors of the new study – Dr Kate Mansfield of the University of Central Florida and Dr Nathan Putman of NOAA’s Southeast Fisheries Science Center in Miami – decided to test this long-standing hypothesis.
The scientists tagged 24 green (Chelonia mydas) and 20 Kemp’s ridley (Lepidochelys kempii) 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.
Next to the turtles, the team deployed passively-drifting surface buoys that were also tracked by satellite.
When the drifter tracks were compared to the sea turtles’ movements, Dr Mansfield and Dr Putman 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 in the first few days.
“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,” Dr Mansfield said.
“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.”
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Nathan F. Putman & Katherine L. Mansfield. Direct Evidence of Swimming Demonstrates Active Dispersal in the Sea Turtle “Lost Years.” Current Biology, published online April 09, 2015; doi: 10.1016/j.cub.2015.03.014
