It's long been a concern for conservationists that green sea turtles are facing the existential threat of a "man drought".
But researchers say there is a glimmer of hope in southern parts of the Great Barrier Reef.
Heron Island is known for its turtle populations, but 80 per cent of hatchlings from the island are born female.
Now research involving drones shows there is actually an equal gender ratio of mating adult green sea turtles.
University of Queensland PhD candidate Melissa Staines, the lead author of the report, said it was great news.
"Because we know that in the northern Great Barrier Reef, where there's a separate breeding population of green turtles, climate change has had a huge impact on their sex ratios and it's starting to transition into the adult population as well," she said.
"It's good to know that we're still seeing healthy ratios of males and females down here in the southern Great Barrier Reef."
Ms Staines said males returned to mate two to three times more frequently than females.
"Luckily, enough turtles naturally have this mechanism where males are repeatedly going back to breed more frequently than females, and that's primarily because they have less of an investment each breeding season," she said.
She said the team flew a drone for several days in peak breeding season in October 2021 at Heron Island, which was a known courtship site.
"The turtles migrate from their foraging grounds and find a courtship site along the way before they reach a nesting site," Ms Staines said.
She differentiated males from females based on their tail length.
"I was able to record the turtles interacting with each other or chasing after each other," she said.
Research could act as 'blueprint'
The research is part of the World Wide Fund for Nature (WWF) Australia's turtle cooling project, which has been running for four years, working with the University of Queensland, the Conflict Islands Conservation and corporate partners.
WWF's Christine Madden Hof said the research was also about trialling the drone methodology before possibly applying it elsewhere.
"It was really important to do this work, particularly at Heron Island, so that we have that methodology sound, we could look to see what those differences were, then we could take this to other locations" Ms Madden Hof said.
"[As] there are a number of populations around the world that are feminising, [including] the green turtles at Raine Island."
Ms Staines said it was important to know what types of turtles were in an area before doing drone surveys.
"We're hoping that this paper acts as a little blueprint for other people that might want to do it in their place around the world," she said.
Population bounces back
Ms Madden Hof said the southern Great Barrier Reef green sea turtle population had recovered to healthy numbers after being decimated by a turtle cannery on Heron Island a century ago.
"We are seeing them rebounding, but that's not to say that we should not take our finger off the pulse and keep a watchful eye on this population," she said.
"This study showed that the population is doing OK, on a climate change front."
But she said the population would need to be monitored closely for a number of years to come.
