Conservationists have long worried that green sea turtles face the existential threat of a “human drought”.
- There is hope Heron Island is bucking a trend of rapidly feminizing the world’s green sea turtle population
- New research, using drones, has found that the sex ratio of the adult mating population is equal
- This is probably due to the fact that males return to mate more frequently than females.
But researchers say there is a silver lining in the southern parts of the Great Barrier Reef.
Heron Island is known for its turtle populations, but 80% of hatchlings on the island are born female.
Now, research involving drones shows that there is in fact an equal gender ratio of mating adult green sea turtles.
Melissa Staines, a PhD student at the University of Queensland and lead author of the report, said it was great news.
“Because we know that in the northern Great Barrier Reef, where there is a distinct breeding population of green sea turtles, climate change has had a huge impact on their sex ratio and it’s also starting to affect the adult population,” she said.
“It’s good to know that we still see healthy male to female ratios here in the southern Great Barrier Reef.”
Ms Staines said males returned to mate two to three times more often than females.
“Fortunately, enough turtles naturally have this mechanism where males repeatedly breed more frequently than females, and that’s mainly because they have less investment each breeding season,” she said. declared.
She said the team flew a drone for several days during peak breeding season in October 2021 on Heron Island, which was a known courtship site.
“The turtles migrate from their feeding grounds and find a courtship site along the way before reaching a nesting site,” Ms Staines said.
She differentiated males from females based on the length of their tails.
“I was able to record the turtles interacting with each other or chasing after each other,” she said.
Research could serve as a “blueprint”
The research is part of the four-year World Wide Fund for Nature (WWF) Australian Turtle Chilling Project, in collaboration with the University of Queensland, Conflict Islands Conservation and commercial partners.
WWF’s Christine Madden Hof said the research also aims to test the drone methodology before possibly applying it elsewhere.
“It was really important to do this work, especially on Heron Island, so that we had this solid methodology, we could see what those differences were, and then we could take that to other places,” Ms Madden Hof said.
“[As] there are a number of populations in the world that are becoming feminized, [including] the green turtles of Raine Island.”
Ms Staines said it was important to know what types of turtles were in an area before conducting drone surveys.
“We hope that this document will serve as a small model for others who may want to do this for them in the world,” she said.
The population rebounds
Ms Madden Hof said the Great Barrier Reef’s southern green turtle population had recovered to healthy numbers after being decimated by a turtle cannery on Heron Island a century ago.
“We’re seeing them rebound, but that doesn’t mean we shouldn’t take the pulse and keep a close eye on this population,” she said.
“This study showed that people are doing well on the climate change front.”
But she said the population should be watched closely for a number of years to come.
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