The epic journeys of green sea turtles revealed by 50 years of data

NESTLED among bright yellow tube sponges and corals, this green sea turtle (Chelonia mydas) will soon make its way across the ocean on an epic journey.

Adult green turtles migrate from their breeding grounds and nesting beaches where they lay their eggs to specialised foraging sites that they use for food and refuge. The voyage can stretch for hundreds to thousands of kilometres and is a trip that the turtle will undertake every two to three years throughout its life.

Using more than 50 years of satellite tracking data to follow the paths of sea turtles, Nicole Esteban at Swansea University, UK, and her colleagues have discovered that these animals will skip areas they aren’t familiar with as they travel between foraging sites, even if those areas are seemingly suitable (Journal of Animal Ecology, doi.org/dvqt). The researchers say this may be because the turtles view such places as risky relocation spots, since they don’t know how well they will work as foraging habitats in the long term.

One green turtle that the team tracked was an “incredible illustration” of how faithful these animals are to their foraging sites, says Esteban, travelling 5000 kilometres to the exact spot off the coast of Kenya where it was tagged 12 years previously. This is one of the first studies that demonstrates the turtles’ strict fidelity to foraging sites, she says.