Researchers are using drones to film green turtles mating off Queensland’s Heron Island to answer a crucial question: exactly how many adult males does a healthy population need?
It’s an investigation prompted by the feminisation of some green turtle populations; a process linked to climate change.
In 2018, scientists revealed that for the past few decades nearly all turtles hatching on Raine Island in the northern Great Barrier Reef are 99% female.
It is the nest temperature during incubation which determines the sex of baby sea turtles. Scientists are now concerned that climate change is also increasing nest temperatures on other beaches in the Asia Pacific, resulting in fewer males.
The lack of male hatchlings in the northern GBR has prompted fears for the future of one of the largest green turtle populations in the world, which is thought to already be in decline.
That led to the Turtle Cooling Project, a partnership between the World Wide Fund for Nature-Australia, The University of Queensland, and the Conflict Islands Conservation Initiative with funding support from furniture company Koala.
The project has already shown that pouring sea water on a nest can cool eggs enough to generate male hatchlings.
For the next stage of research, in July and October 2021, scientists used drones to study the ratio of adult males to females prior to and during the breeding season at Heron Island, north east of Gladstone.
Heron Island was chosen as the research site because the sand temperatures are relatively cool and it is a known courtship area for southern GBR green turtles, whose numbers are increasing (unlike the northern GBR population).
“By analysing drone videos, we will be able to determine the ratio of breeding males to females in a healthy and growing population,” said the drone research lead, University of Queensland PhD candidate Melissa Staines.
“This will assist rookery managers to establish if a breeding population is feminising, prompting action such as seawater irrigation to increase male hatchling production,” she said.
Mitchell Taylor, the founder and CEO of Koala, said his company has now achieved the milestone of donating $2 million to WWF to help threatened species.
"Since 2015, Koala has been a proud supporter of WWF-Australia, it's being able to work on projects like this, that make it all worth it to us.
“Over the past six years, we've been dedicated to supporting and protecting endangered species however we can, from koalas to glossy black cockatoos and now turtles.
“It's been fantastic to be able to support the Turtle Cooling Project and help assist research by WWF and its partners, while also achieving a milestone donation, to ensure the longevity of the green sea turtle populations.
“It's exciting to see the direct impact our support has on the biodiversity and protection of the natural habitats of these animals," he said.
Christine Madden Hof, WWF-Australia’s Marine Species Project Manager, said it’s important to act now to protect turtles.
“Turtles take about 30 years to reach sexual maturity so we need to start generating some males now in those populations which are feminising,” Ms Madden Hof said.
“We now have 20 hours of drone video ready for analysis, providing fascinating insights into turtle mating behaviour.
“Soon we will be in a position to offer this methodology and technology for use in other nearby locations such as the courtship area of the feminising northern GBR green turtle population, so we can work out just how many males we need to produce before it’s too late.
“Saving green turtles and other threatened species requires funding and Koala has really stepped up. We are sincerely grateful and congratulate the amazing team at Koala on reaching the milestone of $2 million in donations to WWF,” she said.