An estimated 64,000 endangered green turtles have been visually captured migrating off the coast of Australia’s Raine Island – the world’s largest green turtle rookery – in a dazzling display of drone technology.
The footage was captured in 2019 as part of the Raine Island Recovery Project, an effort dedicated to preserving the remote coral cay. Researchers here are working to rebuild nesting beaches and put up fences to prevent turtle deaths for the 60,000+ female green turtles that come to the region every year to lay eggs in one of the planet’s “greatest animal migrations". Green turtles (Chelonia mydas) are listed as endangered on the IUCN Red List with populations decreasing in large part due to a loss of habitat and overfishing of resources.
Since 1984, researchers have been estimating turtle populations on Raine Island by marking thousands of the turtles with paint – a difficult and time-consuming task – before visually counting individual animals.
“Previous population survey methods involved painting a white stripe down the green turtles’ shell when they were nesting on the beach. The paint is non-toxic and washes off in a couple of days,” said Dr Andrew Dunstan from the Queensland Department of Environment and Science in a statement. “From a small boat, we then counted painted and non-painted turtles, but eyes are attracted much more to a turtle with a bright white stripe than an unpainted turtle, resulting in biased counts and reduced accuracy.”
In December 2019, researchers employed the use of Unmanned Aerial Vehicles (UAVs), or drones, to investigate whether more technologically advanced strategies might be more efficient. The team took the footage and analyzed it frame-by-frame in the lab to count the turtles to compare it against the old-fashioned way and the use of underwater Go-Pro footage. The results, which are published in the journal PLOS ONE, showed that drone use is not only the “most efficient survey method,” but is also safer, more accurate, and allows for the data to be permanently stored.
“We’re seeing the world’s largest aggregation of green turtles captured in these extraordinary drone images that are helping to document the largest turtle numbers seen since we began the Raine Island Recovery Project,” said Great Barrier Reef Foundation Managing Director Anna Marsden.
Researchers also determined that surface observers “consistently reported higher proportions of marked turtles” than either UAV of underwater method, which yielded higher population estimates that may have skewed conservation efforts.