Young sea turtles follow the path

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How do young sea turtles behave during their early days in the open sea? This question has so far been difficult to answer, because for a long time there were no suitable methods to engage trackers for small, fast-growing marine animals. Now researchers have developed such a technique and used it to monitor 21 young green sea turtles by satellite for about half a year. The gait pattern of animals is therefore more complex than before. Instead of passively drifting themselves, they actively swim in preferred areas. The Sargasso Sea in the North Atlantic is a particularly important habitat for endangered species.

As “green turtles” they were hunted until nearly extinction. Today they are at risk of climate change and destruction of their habitat: Green sea turtles (Chelonia mydas) are endangered and under international protection. Information about how turtles live, migrate and breed is important in species conservation efforts. But this is the data sketch. In particular, there is little information about the early life stages of marine animals. One reason for this: Since young turtles grow quickly, it is difficult to attach a satellite tracker to their shell that will stick to it for a long time, but will not affect the growth or other welfare of the animal. The previous findings are therefore primarily based on short-term observations and vision.

New tracking method

A team led by Catherine Mansfield from the University of Central Florida in Orlando has now developed a tracking method specifically for young green sea turtles and has tracked 21 individuals for 152 days using it. All turtles were collected on a beach in Florida, placed in large tanks in the university’s marine laboratory for three to nine months immediately after etching, until they weighed at least 300 grams . Researchers then equipped them with solar powered satellite trackers and released them near their birth beach in the Gulf Stream.

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Mansfield and colleagues already had experience tracking sea turtles with the loggerhead turtle (Carreta carreta), which they also observed via satellite as young animals. “The green sea turtle shell has a different structure and a waxy surface, so we had to develop a new method to attach the tracker,” the researchers report. After several unsuccessful attempts, in which the trackers fell again after a few days, the researchers found a solution: before they applied the special adhesive, they lightly sanded the waxy layer onto the tank. That’s when he attached the satellite tracker. According to the researchers, this method can also help observe green sea turtles for several months in the future.

Sargasso Lake as a rearing residence

“Our data suggest that the behavior of green sea turtles is more complex than ever,” Mansfield and colleagues report. While it was previously believed that the animals were primarily passively driven, new data clearly shows that the animals are actively oriented and swimming out of large streams such as the Gulf Stream. A particularly popular destination is apparently the Sargasso Sea, a sea area in the Atlantic Ocean east of Florida, which takes its name from the abundant brown algae of the Sargasum genus. “Two-thirds of our tracked green sea turtles were in the waters of the Sargso Sea when their tag transmissions stopped,” the researchers report. “This suggests that many Atlantic green sea turtles use the Sargasso Sea as breeding habitat.”

Sargasso Sagar provides young turtles with plenty of food, a certain protection from predators and a good temperature to grow. The researchers said, “In this study the turtles stayed in the ocean surface layer and received thermal benefits from exposure to direct sunlight on the ocean surface.” How long the turtles live in the Sargasso Sea and why not all individuals have a lot of herds is still unclear. For example, it would be predictable that smaller, weaker swimmers initially live in larger streams. Researchers would like to clarify this in future studies with more green sea turtles of different eras.

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Search for species protection

The researchers compared their results with previous findings on paralyzed turtles from the same area. Accordingly, the routes and movement patterns of the two species differ, but for both, the Sargasso Sea is an important stop in the early life course. “Now that more and more data are available on the first years of sea turtles in the North Atlantic, it is clear that the Sargasso Sea is an important development and rearing habitat for sea turtles,” the authors write. Therefore it is particularly important to preserve this habitat. “Understanding early behavior and identifying early growth habitats is critical to the successful management and conservation of this endangered species,” Mansfield and colleagues said.

Quail: Catherine Mansfield (University of Central Florida, Orlando) et al., Proceedings of the Royal Society B: Biological Sciences, Doi: 10.1098 / r dioxide. 2021.0057

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