WEBVTT - Sea Turtles Are Hatching Up to 99 Percent Female

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<v Speaker 1>Welcome to brain stuff from how stuff works, Hey, brain

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<v Speaker 1>stuff loin vocal bomb here. Australia's Great Barrier Reef is

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<v Speaker 1>an enormous climate change experiment that's not happening in the

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<v Speaker 1>safe isolation of a laboratory. Instead, the warming waters off

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<v Speaker 1>the east coast of the continent have a profound real

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<v Speaker 1>world effect on thousands of miles of coral as well

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<v Speaker 1>as the animals that live there. For decades, scientists have

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<v Speaker 1>suspected that increases in ocean's temperatures would affect sex ratios

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<v Speaker 1>in certain animals, and research shows that's exactly what's happening

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<v Speaker 1>to the Pacific Green Sea turtles. In most of Earth's creatures,

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<v Speaker 1>gender is determined during the fertilization process. That's not true

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<v Speaker 1>of animals like turtles, crocodiles, and alligators, though, which rely

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<v Speaker 1>on a concept called temperature dependent sex determination, or TDS

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<v Speaker 1>to dictate these sex of their offspring. In the case

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<v Speaker 1>of turtles, warming waters and sands are altering the TDS

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<v Speaker 1>process during the breeding season. The turtles, which can grow

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<v Speaker 1>to nearly five hundred pounds that's about two ms, with

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<v Speaker 1>a shell diameter of four feet or one point two meters,

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<v Speaker 1>flop ashore and bury their eggs in the sand. The

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<v Speaker 1>temperature of that sand determines whether baby turtles will wind

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<v Speaker 1>up with blue or pink flippers. Figuratively speaking, if the

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<v Speaker 1>incubation temperature is below eighty two degrees fahrenheit or thirty

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<v Speaker 1>degrees celsius, the turtles will hatch as males. Above eighty

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<v Speaker 1>eight degrees fahrenheit or thirty one degree celsius, the babies

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<v Speaker 1>will be female. A similar problem has been reported in

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<v Speaker 1>loggerhead turtles on Florida beaches, since scientists have noticed a

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<v Speaker 1>strong bias toward female turtles in some instances. Up to

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<v Speaker 1>to see how varying temperatures might affect turtle populations, scientists

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<v Speaker 1>compared sex ratios of turtles near multiple breeding grounds around

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<v Speaker 1>the Great Barrier Reef. They used blood tests and laparoscopy

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<v Speaker 1>to determine the sex of these animals. At the southern

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<v Speaker 1>edge of the reef, near Brisbane water, temperatures are cooler

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<v Speaker 1>and female turtles out number males by a ratio of

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<v Speaker 1>two to one, about sixty five to sixty nine percent female. However,

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<v Speaker 1>about one thousand, two hundred miles north, in the largest

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<v Speaker 1>and most critical sea turtle rookery in the Pacific Ocean.

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<v Speaker 1>Warmer sea and air temperatures are having a dramatic effect

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<v Speaker 1>of hatchlings are female. Although each male can mate with

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<v Speaker 1>more than one female during a breeding season, a severe

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<v Speaker 1>imbalance in sex ratios doesn't bode well for temperature sensitive

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<v Speaker 1>species like sea turtles. Furthermore, once the incubating sand becomes

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<v Speaker 1>too warm, it outright kills the developing organism, further threatening

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<v Speaker 1>turtle populations. The study was published in January in the

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<v Speaker 1>journal Cell Biology. The researchers write, our study highlights the

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<v Speaker 1>need for immediate management strategies aimed at lowering incubation temperatures

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<v Speaker 1>at key rookeries to boost the ability of local turtle

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<v Speaker 1>populations to adapt to the changing environment and avoid a

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<v Speaker 1>population collapse or even extinction. Today's episode was written by

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<v Speaker 1>Nathan Chandler and produced by Tristan McNeil. For more on

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<v Speaker 1>this and lots of other environmental topics, visit our home planet,

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<v Speaker 1>how stuff Works dot com.