• Green Sea Turtle on a reef in Malaysia

Higher temperatures turn sea turtle broods to nearly all-female

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Higher temperatures turn sea turtle broods to nearly all-female

January 12, 2018 - 21:20
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A new study highlights the population challenges faced by sea turtle populations in the wake of climate change.

Scientist Camryn Allen processes samples from green sea turtles in a field laboratory in the northern Great Barrier Reef.

Whether in person or through video footage, we've all seen pregnant sea turtles laboriously making their way up a beach to lay their eggs in the sand. Did you know that the temperature of the sand determines the gender of the offspring?

Yes, cooler temperatures produce male offspring while warmer temperatures produce female offspring. Unfortunately, with global temperatures continuing to rise, a new study has highlighted the fact that almost all the turtles has been born at nesting beaches on islands in Australia's northern Great Barrier Reef (GBR) in the last twenty years were female.

Green sea turtles do not develop into males or females due to sex chromosomes, like humans and most other mammals do. Instead, the temperature outside a turtle egg influences the sex of the growing embryo.

Using a combination of endocrinology and genetics to assess the gender of hundreds of turtles across a large foraging ground, researchers from NOAA Fisheries and the Queensland Department of Environment and Heritage Protection were able to find out the sex ratios and trends of two nesting populations in the GBR.

The findings of their study was recently published in the current issue of the journal Current Biology.

According to their press release: "Green sea turtles from cooler southern nesting beaches were about 65 to 69 percent female, testing showed. Sea turtles from warmer northern beaches leaned even more heavily female, with 86.8 percent of adult turtles, 99.8 percent of sub-adult turtles, and 99.1 percent of juvenile turtles turning out to be female."

Although having more females in the population may appear to be beneficial in boosting reproductive figures, the turtles may be unable to adapt with the fast pace of the change.

"The pace of change affecting these populations is probably unlike anything they have experienced before," said research biologist and co-author Camryn Allen of NOAA Fisheries' Pacific Islands Fisheries Science Center.

“We know that species evolve in response to climate and other environmental changes, but they need time for that. Unfortunately in this case, that may be one thing they do not have."

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