Sea Turtles Are Hatching Up to 99 Percent Female

A sea turtle's sex is determined by the temperatures in its hatching site, and global warming is making the Great Barrier Reef warmer than ever before. What could this mean for the future of sea turtles?

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Episode Transcript

Speaker 1 (00:02):
Welcome to brain stuff from how stuff works, Hey, brain
stuff loin vocal bomb here. Australia's Great Barrier Reef is
an enormous climate change experiment that's not happening in the
safe isolation of a laboratory. Instead, the warming waters off
the east coast of the continent have a profound real
world effect on thousands of miles of coral as well

(00:22):
as the animals that live there. For decades, scientists have
suspected that increases in ocean's temperatures would affect sex ratios
in certain animals, and research shows that's exactly what's happening
to the Pacific Green Sea turtles. In most of Earth's creatures,
gender is determined during the fertilization process. That's not true
of animals like turtles, crocodiles, and alligators, though, which rely

(00:42):
on a concept called temperature dependent sex determination, or TDS
to dictate these sex of their offspring. In the case
of turtles, warming waters and sands are altering the TDS
process during the breeding season. The turtles, which can grow
to nearly five hundred pounds that's about two ms, with
a shell diameter of four feet or one point two meters,
flop ashore and bury their eggs in the sand. The

(01:05):
temperature of that sand determines whether baby turtles will wind
up with blue or pink flippers. Figuratively speaking, if the
incubation temperature is below eighty two degrees fahrenheit or thirty
degrees celsius, the turtles will hatch as males. Above eighty
eight degrees fahrenheit or thirty one degree celsius, the babies
will be female. A similar problem has been reported in
loggerhead turtles on Florida beaches, since scientists have noticed a

(01:28):
strong bias toward female turtles in some instances. Up to
to see how varying temperatures might affect turtle populations, scientists
compared sex ratios of turtles near multiple breeding grounds around
the Great Barrier Reef. They used blood tests and laparoscopy
to determine the sex of these animals. At the southern
edge of the reef, near Brisbane water, temperatures are cooler

(01:49):
and female turtles out number males by a ratio of
two to one, about sixty five to sixty nine percent female. However,
about one thousand, two hundred miles north, in the largest
and most critical sea turtle rookery in the Pacific Ocean.
Warmer sea and air temperatures are having a dramatic effect
of hatchlings are female. Although each male can mate with
more than one female during a breeding season, a severe

(02:11):
imbalance in sex ratios doesn't bode well for temperature sensitive
species like sea turtles. Furthermore, once the incubating sand becomes
too warm, it outright kills the developing organism, further threatening
turtle populations. The study was published in January in the
journal Cell Biology. The researchers write, our study highlights the
need for immediate management strategies aimed at lowering incubation temperatures

(02:33):
at key rookeries to boost the ability of local turtle
populations to adapt to the changing environment and avoid a
population collapse or even extinction. Today's episode was written by
Nathan Chandler and produced by Tristan McNeil. For more on
this and lots of other environmental topics, visit our home planet,

(02:54):
how stuff Works dot com.