Field Notes: April 2012
Read about the latest Earthwatch discoveries, rare sightings and exciting news reported by volunteers and scientists from the field.
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Costa Rica’s Leatherback Sea Turtles may spend “Lost Years” on hatchling highways: lessons from Playa Grande |
Scientists know so little about the early life history of the critically endangered leatherback turtle, from hatchling to adulthood, that they call this period the “Lost Years.” But a team researching the nesting site of Playa Grande, site of Earthwatch project Costa Rican Sea Turtles, has just helped to fill in some of the gaps - great news for this critically endangered species.
The beach is surrounded by ocean currents that improve the hatchlings’ chances of survival, according to the team of researchers, who include Earthwatch scientist Dr. James Spotila. Their findings were published recently in Proceedings of the Royal Society B: Biological Sciences.
More specifically, Playa Grande’s large-scale eddies - circular currents that move in a different direction to a main current - carry the turtles safely offshore during the nesting period along with other currents, serving as ‘hatchling highways’ to the sea, they said. The currents carry the turtles away from the grips of coastal-dwelling predators, and into the relative safety of the sea where they can do things like munch on jellyfish and grow up. In the case of the females, more than ten years later when they have reached maturity, they return to shore to nest.
The team figured this out by using “passive tracers” - a fluid used to track flow. Between 2000 and 2008, within the January to April nesting period of turtles, the scientists used passive tracers on the waters of four nesting beaches, including Playa Grande. These tracers imitate how young turtles are carried by currents, as hatchlings don’t develop full swimming abilities for the first six months of their lives.
That’s when they saw the eddies and coastal currents, which likely play a critical role in getting the hatchlings safely to sea. This kind of information is significant in helping to better understand the turtle’s ecology and to inform conservation strategies.
Dr. Spotila adds that " The leatherbacks are holding on with their flipper tips, we need to get fishing under control real soon or the turtles will be gone."
The full paper can be found at rspb.royalsocietypublishing.org.
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