Raine Island: World’s largest turtle population in deadly crisis

An island on the Great Barrier Reef is experiencing a serious lack of population growth after it was discovered 99 per cent of its shelled inhabitants were female.

It’s a man drought like no other, threatening to wipe out an entire population, and it doesn’t help that the females aren’t interested in sex in the first place.

But now, drone technology is being used to answer one vital question: how many males do you really need?

Raine Island, on Queensland’s far northern Great Barrier Reef, is home to the world’s largest green turtle nesting population, 99 per cent of which is female due to the impact of climate change.

Raine Island green turtles are in danger after a high female population has halted breeding. Picture: Jason Isley

A turtle’s sex is determined by the heat of the nest, and the warmer the sand in which they hatch the more females are produced.

In a collaboration between the World Wild Fund for Nature and University of Queensland, drones have spectacularly captured the October mating season of a more gender-balanced population, 1560 km south on Heron Island.

The rare footage is being analysed to determine the ideal male-to-female ratio to ensure the survival of the northern reptiles.

WWF scientist Caitlin Smith said it was imperative to act now, with turtles taking 30 years to reach breeding age.

“We are at a crisis point,” Ms Smith said.

“Not only are there hardly any males, but the females really don’t want to mate.

“They have to drag a male around on their backs for several hours while he hangs on with sharp claws and inseminates her.

“It’s exhausting so during courtship, females will make them work for it, and only take the most persistent males.”

Raine Island has no trees for shelter.

Marine biologist Melissa Staines, reviewing the drone footage as part of her PhD research at UQ, said climate change had caused sand temperatures to soar.

“Raine Island is also closer to the equator and devoid of trees for shade, so the turtles are up against it,” Ms Staines said.

The findings, due for release in early 2022, are expected to garner support for measures to cool the sand, such as applying sea water during a critical phase before eggs hatch.

The turtle cooling project is also supported by the Conflict Islands Conservation Initiative with $2m funding from furniture company Koala.