As It Happens

Australian researchers count 64,000 nesting turtles in drone footage — far more than expected

Australian researchers using drones have captured stunning footage of over 64,000 nesting green sea turtles and were surprised to learn the population is much larger than previously thought.

'It actually increased our estimates by about 75 per cent,' Raine Island researcher Andy Dunstan says

Thousands of green turtles are seen swimming just off shore of Raine Island, in the northern end of the Great Barrier Reef, Australia. (Great Barrier Reef Foundation/Queensland Government)
Listen6:08

Australian researchers using drones have captured stunning footage of over 64,000 nesting green sea turtles and were surprised to learn the population is much larger than previously thought.

Every nesting season, the island on the far northern tip of the Great Barrier Reef is swarmed with female turtles looking to lay their eggs, said Andy Dunstan, researcher at the Raine Island Recovery Project at the Queensland Department of Environment and Science.

But until recently, it wasn't clear quite how crowded the rookery actually was.

"They sort of look a bit like a whole sea of small cockroaches [from the drone]. But these turtles are large. They're 1.2 metres across and about 180 kilograms each. So this is an amazing aggregation," Dunstan told As It Happens host Carol Off.   

"The thing to remember with this is you're looking at a two-dimensional image. What you're seeing is the surface, [but] there are turtles all the way underneath them down to 10, 15 metres." 

Dunstan said that it was "fantastic" to see how far afield from the reef the turtles go and the "sheer density" of them.

"We've done similar things in trying to count them from a boat at the surface. You get some idea of that, but you don't get the same concept of it like you do from a drone in the air," he said.

"To be able to count that many turtles and have it actually increased our estimates by about 75 per cent has been fantastic."  

In order to calculate the number of turtles, researchers go out at night and use a non-toxic paint to colour the shells of around 2,000 of the nesting animals. Then when the beach is empty the next day as the animals go swimming, they calculate the ratio between painted and non-painted turtles, he said.  

WATCH I Australian researchers count 65,000 nesting turtles off Raine Island:

Australian researchers using drones have captured stunning footage of over 64,000 nesting green sea turtles and were surprised to learn the population is much larger than previously thought. 3:02

"We count for about three days. Then a few days later, the paint's gone. We're pretty relaxed about painting them on the beach."

Despite the increasing number of turtles spotted around Raine Island, the actual hatching success on its beaches was "not that great," Dunstan said, blaming the water that's inundating the nests as the beach slowly erodes.

"That's why we're putting a lot of work in at the island to try and turn that around. But it is reassuring that we have that many turtles, and we still have time to be able to turn that reproduction around to make sure that it sustains into the future." 

Andy Dunstan, researcher at the Raine Island Recovery Project, says the island is the one of the only major aggregation nesting places in the world for green turtles. (Christian Miller)

Hundreds of adults are also dying yearly because the loss of beach space forces them to nest up near the edge of the island's cliffs, Dunstan said.

They fall onto their backs, then they have no way to right themselves in order to make it back to the water, he said. 

"We've been able to put up a small fence and totally stop the cliff fall deaths and rescue turtles and get them back to the ocean while we're there. So, you know, saving hundreds and hundreds a year." 

Dunstan said that all that hard work is worth it, and that after 10 years of caring for the nesting turtles, it's still "just magnificent" to be around the endangered animal every day.

"This is the only major aggregation nesting places in the world for green turtles, and it's one of the few major healthy remaining populations. Even now, it's still suffering from hatching failure and a range of other things," he said. 

"I'm an optimist, and the work that's going on here is quite incredible. Some of the work that we're doing, particularly in partnership with the traditional owners and Indigenous groups up and down the reef, is fabulous."  


Written by Adam Jacobson. Produced by Morgan Passi.

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