Warm temperatures turning sea turtle population almost entirely female

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AS temperatures continue to rise, sea turtle demographics are changing to the point where the long-term sustainability of the species may be in question.

New data analysed by researchers in the United States and Australia suggests that warming temperatures are turning one of the world’s largest sea turtle colonies almost entirely female, putting the future of the species at risk in the coming decades.

The sex of turtle hatchlings is determined by sand temperatures, with warmer temperatures resulting in more females.

Over the course of the last two decades, temperature have increased in Australia’s northern Great Barrier Reef, which holds some of the largest turtle populations in the world, to the point where there are virtually no male turtles being produced from the nesting beaches.

Researchers previously determined the sex of individual hatchlings through anatomical exams at nesting beaches, providing only a snapshot in time from only a few nests.

In the new study, the researchers used a combination of endocrinology and genetics to assess the sex of hundreds of turtles across a large foraging ground to reveal the sex ratio of immature and mature turtles from different nesting beaches over many years.

The analysis showed different sex ratios and trends in two nesting populations in the
Great Barrier Reef. Green sea turtles from cooler southern nesting beaches were about
65 to 69 percent female, while sea turtles from warmer northern beaches were 86.8 percent female for adult turtles, 99.8 percent for sub-adult turtles, and 99.1 percent for juvenile turtles.

“This has given us an important new window into demographic changes in these populations over the last several decades, which have gone undetected until now,” Michael
Jensen, a research biologist at NOAA Fisheries’ Southwest Fisheries Science Center in La
Jolla, Calif., and lead author of the new research, said in a statement. “The disconcerting
thing is that we can now see how changes in the climate could affect the longevity of this and other sea turtle populations around the world.”