Study: Female/Male Sex Ratio In Raine Island Sea Turtles Now 116 To 1 (Yes, Becuse Of Warming)
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Allen, a scientist with the National Oceanic and Atmospheric Administration in Hawaii, had spent her early career using hormones to track koala bear pregnancies. Then she started using similar techniques to help colleagues quickly answer a surprisingly hard question: whether a sea turtle is male or female. You can't always tell which is which just by looking. That often requires laparoscopy, viewing the turtle's internal organs by inserting a thin camera. Allen figured out how to do it using blood samples, which made it easier to check lots of turtles quickly.
That mattered because the heat of sand where eggs are buried ultimately determines whether a sea turtle becomes male or female. And since climate change is driving up temperatures around the world, researchers weren't surprised that they'd been finding slightly more female offspring.
But when Allen saw results from her research on Raine Island, Australia—the biggest and most important green sea turtle nesting ground in the Pacific Ocean—she realized how serious things might get. Sand temperatures there had increased so much, she and a team of scientists reported last year, that female baby turtles now outnumber males 116 to 1.
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More than 200,000 sea turtles nest on or near Raine, a tiny 80-acre curl of sand along the northern edge of the Great Barrier Reef, the portion hardest hit by warming waters. The other portion of that sea turtle population nests further from the equator, near Brisbane, where temperature increases have not been as dramatic. What Allen and Jensen discovered was significant. Older turtles that had emerged from their eggs 30 or 40 years earlier were also mostly female, but only by a 6 to 1 ratio. But younger turtles for at least the last 20 years had been more than 99 percent female. And as evidence that rising temperatures were responsible, female turtles from the cooler sands near Brisbane currently still only outnumber males 2 to 1.
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https://www.nationalgeographic.com/environment/2019/04/sea-turtle-sex-ratio-crisis-from-climate-change-has-hope/
