The world’s largest population of nesting green turtles is nearly twice as big as previously thought, scientists said, after drones enabled better surveys of the animals. 

Australian scientists determined that there were about 64,000 green turtles waiting to lay eggs on Raine Island — a vegetated coral cay on the outer edges of the Great Barrier Reef — significantly more than thought. 

“When we compared drone counts to observer counts we found that we had under-estimated the numbers in the past by a factor 1.73,” Richard Fitzpatrick, research partner at Biopixel Oceans Foundation said. The research is good news for scientists concerned about declining numbers of green turtles. 

Listed as endangered, many countries have made it illegal to collect or harm them, while nesting grounds are often also protected. But getting an accurate picture of how the species is responding to protection efforts has been difficult. 

Earlier, researchers would paint a non-toxic white stripe down the turtles' shells and would count them, those with and without white stripes, from a small boat. But this way of counting proved inaccurate due to poor visibility, the researchers said.

Green turtle

The scientific name of green turtle is Chelonia mydas. Green turtles are named for the greenish color of their cartilage and fat, not their shells. They are found mainly in tropical and subtropical waters. Like other sea turtles, they migrate long distances between feeding grounds and the beaches from where they hatched. 

Raine Island

Raine Island is located on the northern tip of the Great Barrier Reef, approximately 620 kilometres north-west of Cairns. The vegetated coral cay is just 21 hectares in size, but holds significant environmental and cultural values. The entire island is a protected national park.

Raine Island is the site of the world’s largest known rookery in the Great Barrier Reef World Heritage Area for internationally endangered green turtles which come ashore in the tens of thousands to nest each year. Raine Island is also the most significant seabird rookery in the Great Barrier Reef World Heritage Area.

Main features of Raine Island

* Supporting the world’s largest remaining green turtle nesting population. 

* Home to a stone beacon, constructed in 1844, which is a landmark of national cultural significance listed on the Queensland Heritage Register.

* Located in a remote area of the Great Barrier Reef that was the site of numerous shipwrecks, particularly during the 1800s, and even today remains poorly charted.

Changes in the island’s landscape have caused tidal inundation — killing newly laid eggs which cannot survive underwater — and causing as many as 2,000 adult turtles in a season to die from overturning and entrapment in rocky cliffs and from heat exhaustion on the nesting beach.

This, combined with general habitat loss, boat strikes, over harvesting and pollution, has placed the green turtle in serious danger.

Raine Island National Park (Scientific) was created in August 2007 to protect the natural and cultural values of the island and cays. As turtles and seabirds nest on the ground and are easily disturbed, access to the park is restricted to scientific and conservation purposes only. No public access is permitted on Raine Island or its adjacent cays.

The Raine Island Recovery Project aims to protect and restore the island’s critical habitat to ensure the future of key marine species, including green turtles and seabirds.

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