Scientists from Duke University and UNC-Chapel Hill have found a powerful new weapon for counting elusive sea turtles: camera-equipped drones.
A drone equipped with a high-resolution digital camera with near-infrared vision helped researchers document hundreds of thousands of olive ridley sea turtles coming ashore to lay eggs in Costa Rica, the Durham school said.
The fixed-wing drone flew 300 feet above the water off the Ostional National Wildlife Refuge, offering an expanded view and the ability to let researchers spot turtles swimming just below the ocean’s surface. Spotters from boats might easily have missed the submerged animals.
Researchers estimated that nearly 2,100 turtles per square kilometer packed the area during peak nesting season.
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“These are extraordinary numbers, much higher than any of us anticipated,” Seth Sykora-Bodie, a PhD student at Duke’s Nicholas School of the Environment, said in a release from Duke. Sykora-Bodie co-led the study with Vanessa Bézy, a Ph.D. candidate at UNC-CH.
“Our findings confirm drones can be used as a powerful tool to study sea turtle abundance at sea, and reveal incredible densities of turtles in Ostional’s near-shore habitat,” Bézy added. “The development of this methodology provides vital new insights for future conservation and research.”
Two previous Duke University studies showed that drones can be as effective as traditional aircraft for conducting wildlife population assessments. The studies used drones to count gray seals on remote islands off the coasts of eastern Canada and New England.
Sykora-Bodie and Bézy published their findings – the first study to use drones to estimate sea turtle numbers – last month in the journal Scientific Reports. Most studies have been done from the water or by counting turtles on nesting beaches.
Olive ridley sea turtles are classified internationally as vulnerable, chiefly because of the threat of being accidentally caught on fishing gear used by longline and trawl fisheries.