1 00:00:02,040 --> 00:00:06,880 Speaker 1: Welcome to brain stuff from how stuff works, Hey, brain 2 00:00:06,920 --> 00:00:10,159 Speaker 1: stuff loin vocal bomb here. Australia's Great Barrier Reef is 3 00:00:10,160 --> 00:00:13,319 Speaker 1: an enormous climate change experiment that's not happening in the 4 00:00:13,360 --> 00:00:17,000 Speaker 1: safe isolation of a laboratory. Instead, the warming waters off 5 00:00:17,000 --> 00:00:19,320 Speaker 1: the east coast of the continent have a profound real 6 00:00:19,360 --> 00:00:22,079 Speaker 1: world effect on thousands of miles of coral as well 7 00:00:22,120 --> 00:00:25,159 Speaker 1: as the animals that live there. For decades, scientists have 8 00:00:25,200 --> 00:00:28,720 Speaker 1: suspected that increases in ocean's temperatures would affect sex ratios 9 00:00:28,760 --> 00:00:32,120 Speaker 1: in certain animals, and research shows that's exactly what's happening 10 00:00:32,120 --> 00:00:35,879 Speaker 1: to the Pacific Green Sea turtles. In most of Earth's creatures, 11 00:00:35,960 --> 00:00:39,600 Speaker 1: gender is determined during the fertilization process. That's not true 12 00:00:39,640 --> 00:00:42,760 Speaker 1: of animals like turtles, crocodiles, and alligators, though, which rely 13 00:00:42,880 --> 00:00:46,960 Speaker 1: on a concept called temperature dependent sex determination, or TDS 14 00:00:47,000 --> 00:00:49,680 Speaker 1: to dictate these sex of their offspring. In the case 15 00:00:49,720 --> 00:00:53,279 Speaker 1: of turtles, warming waters and sands are altering the TDS 16 00:00:53,360 --> 00:00:56,880 Speaker 1: process during the breeding season. The turtles, which can grow 17 00:00:56,920 --> 00:00:59,840 Speaker 1: to nearly five hundred pounds that's about two ms, with 18 00:00:59,880 --> 00:01:02,400 Speaker 1: a shell diameter of four feet or one point two meters, 19 00:01:02,720 --> 00:01:05,600 Speaker 1: flop ashore and bury their eggs in the sand. The 20 00:01:05,640 --> 00:01:08,560 Speaker 1: temperature of that sand determines whether baby turtles will wind 21 00:01:08,640 --> 00:01:12,160 Speaker 1: up with blue or pink flippers. Figuratively speaking, if the 22 00:01:12,200 --> 00:01:15,319 Speaker 1: incubation temperature is below eighty two degrees fahrenheit or thirty 23 00:01:15,319 --> 00:01:18,399 Speaker 1: degrees celsius, the turtles will hatch as males. Above eighty 24 00:01:18,400 --> 00:01:21,080 Speaker 1: eight degrees fahrenheit or thirty one degree celsius, the babies 25 00:01:21,120 --> 00:01:24,399 Speaker 1: will be female. A similar problem has been reported in 26 00:01:24,480 --> 00:01:28,600 Speaker 1: loggerhead turtles on Florida beaches, since scientists have noticed a 27 00:01:28,640 --> 00:01:32,959 Speaker 1: strong bias toward female turtles in some instances. Up to 28 00:01:32,959 --> 00:01:36,800 Speaker 1: to see how varying temperatures might affect turtle populations, scientists 29 00:01:36,800 --> 00:01:39,960 Speaker 1: compared sex ratios of turtles near multiple breeding grounds around 30 00:01:40,040 --> 00:01:43,120 Speaker 1: the Great Barrier Reef. They used blood tests and laparoscopy 31 00:01:43,240 --> 00:01:46,160 Speaker 1: to determine the sex of these animals. At the southern 32 00:01:46,280 --> 00:01:49,040 Speaker 1: edge of the reef, near Brisbane water, temperatures are cooler 33 00:01:49,080 --> 00:01:51,600 Speaker 1: and female turtles out number males by a ratio of 34 00:01:51,640 --> 00:01:55,680 Speaker 1: two to one, about sixty five to sixty nine percent female. However, 35 00:01:55,880 --> 00:01:58,680 Speaker 1: about one thousand, two hundred miles north, in the largest 36 00:01:58,680 --> 00:02:01,200 Speaker 1: and most critical sea turtle rookery in the Pacific Ocean. 37 00:02:01,520 --> 00:02:05,120 Speaker 1: Warmer sea and air temperatures are having a dramatic effect 38 00:02:05,960 --> 00:02:08,840 Speaker 1: of hatchlings are female. Although each male can mate with 39 00:02:08,880 --> 00:02:11,360 Speaker 1: more than one female during a breeding season, a severe 40 00:02:11,440 --> 00:02:14,680 Speaker 1: imbalance in sex ratios doesn't bode well for temperature sensitive 41 00:02:14,680 --> 00:02:18,440 Speaker 1: species like sea turtles. Furthermore, once the incubating sand becomes 42 00:02:18,480 --> 00:02:22,040 Speaker 1: too warm, it outright kills the developing organism, further threatening 43 00:02:22,040 --> 00:02:25,679 Speaker 1: turtle populations. The study was published in January in the 44 00:02:25,720 --> 00:02:29,520 Speaker 1: journal Cell Biology. The researchers write, our study highlights the 45 00:02:29,560 --> 00:02:33,400 Speaker 1: need for immediate management strategies aimed at lowering incubation temperatures 46 00:02:33,560 --> 00:02:36,280 Speaker 1: at key rookeries to boost the ability of local turtle 47 00:02:36,320 --> 00:02:39,280 Speaker 1: populations to adapt to the changing environment and avoid a 48 00:02:39,320 --> 00:02:48,640 Speaker 1: population collapse or even extinction. Today's episode was written by 49 00:02:48,720 --> 00:02:51,440 Speaker 1: Nathan Chandler and produced by Tristan McNeil. For more on 50 00:02:51,480 --> 00:02:54,640 Speaker 1: this and lots of other environmental topics, visit our home planet, 51 00:02:54,760 --> 00:03:07,560 Speaker 1: how stuff Works dot com.