Where do the endangered green sea turtles spend their early years?
Newly hatched turtles climb out of their sandy nests on tropical and subtropical beaches worldwide, and scramble into the sea. The half-dollar sized hatchlings disappear into the ocean and are not seen again for several years. When the turtles have grown to the size of a dinner plate, they return to shallower waters near the coast and feed on sea grass and other plants. Knowing where the turtles are has been a critical missing link in efforts to protect this amazing species.
Now scientists have found an important clue explaining what the sea turtles are doing in the years between hatching and returning to the coastal regions.
Rather than searching the oceans to solve the puzzle, biologists at the University of Florida turned to “stable isotope analysis,” a technique that has become increasingly useful in tracking ecological history. Animals that are higher on the food chain accumulate more heavy isotopes than those lower on the food chain.
Researchers compared heavy to light isotope ratios in turtles that had recently returned from the open ocean with ratios in turtles that had spent at least a year living along the coasts grazing on plants. Surprisingly, they found that the ratio of heavy isotopes was significantly higher in the new arrivals than in the older resident turtles.
The results suggest that green turtles likely spend their first three to five years as carnivores, eating small jellyfish and other prey in the open ocean, and then dramatically change their behavior and diet to coastal plant-eating.
The interesting study brings scientists one step closer to tracking the turtles’ location during their early life, and furthering efforts to protect this endangered species.