What do those cute little baby sea turtles do after their epic sprint to the water? Until very recently, we simply didn’t know. Nobody had been able to study the movement of juvenile sea turtles in natural conditions – they were simply too small and too difficult to track. But a new study reveals for the first time just what the young turtles have been up to in the Pacific ocean – and it shows that they are just as determined and tenacious as they were on land, fighting strong currents to reach their preferred feeding grounds.

The movements of adult sea turtles are well documented, following ancient migratory routes, from ocean foraging sites to the beaches where they lay their eggs. But because of their small size, nobody knew exactly where the young turtles were going for the first years after hatching. Publishing in Proceedings B on the 1st June, Dana Briscoe from The Hopkins Marine Station in Monterey and her team report the first ever study of juvenile loggerhead turtles in the Pacific ocean during their ‘lost years’ between hatching and adulthood.

Using long-term tracking data coupled with ocean circulation models, the team showed that far from being passively carried by ocean currents, young turtles actively swim to reach the best foraging grounds. Over many years, the turtle’s paths different significantly from those predicted by computer-simulated ocean current trajectories.

“Much more is known about juvenile loggerheads in the Atlantic. We’re excited to understand more about the movements and distribution of endangered loggerhead sea turtles in the North Pacific, during such a critical life history stage”, says Dr Dana Briscoe.

The team tracked 44 loggerhead sea turtles aged between 1 and 3 years old after their release off the coast of Japan. They followed these young turtles for up to four years after their release, and found that they dispersed over a wide area, encompassing nearly the entire width of the North Pacific Ocean. Significant differences between the dispersal pattern predicted based on ocean circulation models showed that the young turtles were swimming against the currents. Many turtles converge in regions where the currents bring food, such as the Kuroshio Extension System, where previous studies have also reported congregations of juvenile turtles.

Understanding how these fragile young turtles navigate the vast open oceans could help conservationists better protect their dwindling populations.

Want to know more?

• Briscoe, Parker, Balazs, Kurita, Saito, Okamoto, Rice, Polovina and Crowder (2016) Active dispersal in loggerhead sea turtles (Caretta caretta) during the ‘lost years’ Proceedings B

Featured image copyright of Hoyt Peckham, used with permission.