Researchers in Australia captured the moment that thousands of turtles congregated on the edge of Australia’s great barrier reef during the nesting season.
Using drones, scientists from the Queensland government’s department of environment and science were able to capture aerial footage of the event.
It took place at Raine Island, which is the world’s biggest "turtle rookery" – the breeding grounds for turtles and other mammals which live in and around the sea.
They’re called green turtles because of the colour of their cartilage and fat.
This particular breed of turtle is endangered – they’ve often been hunted for their eggs, and many get trapped in fishing nets.
Historically, researchers have tried to paint turtles with stripes to identify them but have realised that wasn’t the most efficient or accurate way of determining what their migration and mating patterns were.
Around December of last year, they found that using drones to monitor them was more accurate. It also led them to realise that they had previously been undercounting their numbers, and that they could go back and revise historical estimates.
"Trying to accurately count thousands of painted and unpainted turtles from a small boat in rough weather was difficult. Using a drone is easier, safer, much more accurate, and the data can be immediately and permanently stored," Dunstan, senior research scientist and lead author of the paper, said in a statement.
With the drone, they were able to estimate that there were around 64,000 turtles swimming around Raine Island, coming on shore to lay their eggs.
This is almost 1.4 times as many as they had expected – for the researchers, this was a long-awaited bit of good news.