Photo: Jim Abernethy for Upwell
Nearly 70 years have passed since the famed sea turtle biologist Archie Carr coined the term the “lost years” to describe the poorly understood period of time after sea turtles depart their natal beaches until they return to nearshore waters or nesting beaches. New technologies are finally shedding light on one of the greatest mysteries in sea turtle biology. Using prototype “micro-satellite” tags specifically designed to fit juvenile leatherback turtles, Upwell and Florida Atlantic University researchers released eighteen captive-reared juvenile leatherbacks off the coast of Florida and tracked their movements.
The tags, designed by Lotek Wireless, transmit data on the turtles’ locations as they travel into the influence of the Gulf Stream. The data helps us better understand where the very young turtles go and how they use ocean environments. Without these important pieces of the puzzle we cannot design adequate management and conservation measures to protect leatherbacks at all life history stages.
““Learning more about the movements of juvenile sea turtles helps us to identify key actions that can assist conservation efforts in marine environments.” — Dr. George Shillinger, Executive Director of Upwell”
A cross-disciplinary team contributed expertise from a diversity of scientific fields, including sea turtle husbandry, wildlife telemetry, oceanographic modeling, and conservation biology. Eighteen juvenile turtles were raised at the FAU’s Marine Lab at the Gumbo Limbo Environmental Complex by Dr. Jeanette Wyneken’s staff. Dr. Wyneken has worked for nearly two decades honing techniques for captive reading different sea turtle species. (For leatherbacks, Dr. Wyneken had to create an artificial jellyfish with appropriate protein, fat and minerals. Starting with gelatin, french bread and mussels, she has since continued to refine the diet and make improvements in consultation with a veterinary nutritionist.)
Juvenile turtles grow fast. Once their weight exceeds 100 grams, they are large enough to be outfitted with “micro-satellite” tags. Whereas adult leatherbacks are often equipped with multi-sensor tags designed to transmit for a year or longer; the new very lightweight tags designed for small juvenile leatherbacks are designed to collect only turtle location data. The design allows growing turtles to naturally “shed” the tag around 80 days after deployment.
Releasing juvenile sea turtles is not as simple as transporting them to the beach and letting them swim out from shore, as with hatchling releases. Juveniles are larger, less frenetic than hatchlings, and should be offshore at the 100+ gram size. They stand a better chance at evading predators in nearshore zones than tiny hatchlings, but transporting them offshore allows them to follow natural dispersal patterns in addition to maximizing their chances of survival by circumventing impacts from near-shore predators.
Upwell partnered with Dr. Philippe Gaspar and colleagues at Mercator Ocean International (Toulouse, France) to apply a high-resolution ocean circulation model to select release locations 25-80 kilometers off the coast of Palm Beach County between Florida and the Bahamas. Dr. Gaspar commented, “As a physical oceanographer with a passion for sea turtles, leatherbacks in particular, I am very excited to contribute to this novel experiment in which the oceanographic expertise of my lab is helping unravel the “lost years” mystery. I am eager to discover how the ocean influences the fate of their populations.”
Dr. Wyneken and FAU laboratory technician Emily Turla prepared the turtles for release into the ocean. Dr. Michael Salmon and Dr. Shillinger joined Dr. Wyneken and Emily for the releases. The scientific team motored out to the selected offshore locations aboard the MV Shear Water with award-winning photographer and filmmaker Jim Abernethy and videographer Greg Wilson. Abernethy captured stunning footage of the historic event as the team individually released the juvenile leatherbacks, each outfitted with a transmitter. Dr. Shillinger and others from the team accompanied individual turtles into the water and carefully monitored them while they swam to ensure they were able to move freely with the satellite tag attached. If any turtle showed signs of stress, the researchers would have detached the satellite tag. Fortunately, the turtles all swam well with the tags in place.
Dr. Wyneken shared her perspective on the importance of the research: “It is heartening to see that there is a way forward for this endangered species. There is an awful lot of biology going on between the hatchling and adult stage and we need to understand the biology between a few-centimeter leatherback and a meter-long leatherback. We can’t do that without understanding where their nurseries are.”
Upwell will continue to monitor the satellite tracks and apply the data collected to refine the STAMM model, examine overlap with areas of high-risk from human impacts (e.g., fishing, vessel traffic and plastic aggregation) and support conservation actions to protect juvenile turtles. Dr. Shillinger is enthusiastic about the new insights in sea turtle ecology, satellite tag engineering, and oceanographic modeling this collaborative research yields. He says, “We look forward to analyzing the results from this pioneering study towards continued efforts to demystify the ‘lost years’ period and applying our findings to inform conservation and management efforts during these vulnerable life history stages.”