Too hot for turtle guys: Great Barrier Reef is dangerously warm for male green sea turtles | All media content | DW | 16.02.2018

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Science

Too hot for turtle guys: Great Barrier Reef is dangerously warm for male green sea turtles

Because of warming climates, green sea turtles at the Great Barrier Reef are having female babies almost exclusively. This could lead to the end of the entire species.

  • Meeresschildkröte (picture alliance/dpa/Prisma/R. Mohammed)

    Single green females only?

    In the largest green sea turtle colony, a lopsided majority of newborn babies are female. Male turtles hatch from just one percent of the eggs around the Great Barrier Reef. Researchers now fear for the survival of the species.

  • Schildkröten (Imago/Nature Picture Library/Zankl)

    Too hot for guys

    When sea turtles first lay their eggs, it's not initially clear whether male or female young ones will hatch. That's determined by the temperature of their surroundings. The hotter the sand, the higher the probability that babies will be female. From 29.9 degrees Celsius upward, there won't be little turtle boys. And because of global warming, this benchmark is exceeded more and more frequently.

  • Schildkröten (Imago/imagebroker)

    Male or female? Hard to tell

    It's difficult to determine a sea turtle's sex. You can only tell for sure once the animal is fully grown - and that takes at least 20 years. That is probably why the surplus of females has gone unnoticed for so long. One way to tell the sexes apart: Male turtles have a longer tail and longer claws.

  • Meeresschildkröte (Getty Images/M. Kolben)

    Worrying numbers

    Now, researchers from the US and Australia have developed a method to determine the sex of green sea turtles via DNA and blood tests while the animals are still young. What they didn't expect is that today already, 90 percent of green sea turtles at the Great Barrier Reef are female.

  • Schildkröten (Imago/StockTrek Images)

    Sex is a rare treat

    The small number of males is not the only challenge for green sea turtles. They are only sexually mature at 15, and even then, they only have sex every three years on average. Evolutionary speaking, a small female surplus in populations is nothing out of the ordinary. But the turtles cannot survive entirely without men.

  • Schildkröten (Imago/Zuma Press)

    200 turtle babies in one nest

    Female sea turtles return to the beach where they hatched to lay their own eggs again and again. On Raine Island's beach, the largest nesting ground for green sea turtles in the Pacific, you can find up to 18,000 animals during high season. After the eggs have been warmed by sun and sand long enough, the babies hatch, make their way into the sea and only return once it's their time to lay eggs.

  • Korallenriffe Great Barrier Reef in Australien (Imago/ZUMA Press)

    Female surplus across the world?

    Researchers believe there's a lack of male sea turtles across the world. That's why they're examining the effect that rising temperatures have had on green sea turtle populations along the coasts of Hawaii and on the island of Saipan in the western Pacific. The early gender detection method could lead to surprising results there as well.

  • Krokodil (Imago/OceanPhoto)

    Dangerous heat

    The results of the Australian study are bad news for other animals as well. Other reptiles, like crocodiles or lizards, also develop their sex due to temperature. With alligators, things work in exactly the opposite way as they do with sea turtles: If it gets too hot, only male babies hatch from their eggs.


  • Meeresschildkröte (picture alliance/dpa/Prisma/R. Mohammed)

    Single green females only?

    In the largest green sea turtle colony, a lopsided majority of newborn babies are female. Male turtles hatch from just one percent of the eggs around the Great Barrier Reef. Researchers now fear for the survival of the species.

  • Schildkröten (Imago/Nature Picture Library/Zankl)

    Too hot for guys

    When sea turtles first lay their eggs, it's not initially clear whether male or female young ones will hatch. That's determined by the temperature of their surroundings. The hotter the sand, the higher the probability that babies will be female. From 29.9 degrees Celsius upward, there won't be little turtle boys. And because of global warming, this benchmark is exceeded more and more frequently.

  • Schildkröten (Imago/imagebroker)

    Male or female? Hard to tell

    It's difficult to determine a sea turtle's sex. You can only tell for sure once the animal is fully grown - and that takes at least 20 years. That is probably why the surplus of females has gone unnoticed for so long. One way to tell the sexes apart: Male turtles have a longer tail and longer claws.

  • Meeresschildkröte (Getty Images/M. Kolben)

    Worrying numbers

    Now, researchers from the US and Australia have developed a method to determine the sex of green sea turtles via DNA and blood tests while the animals are still young. What they didn't expect is that today already, 90 percent of green sea turtles at the Great Barrier Reef are female.

  • Schildkröten (Imago/StockTrek Images)

    Sex is a rare treat

    The small number of males is not the only challenge for green sea turtles. They are only sexually mature at 15, and even then, they only have sex every three years on average. Evolutionary speaking, a small female surplus in populations is nothing out of the ordinary. But the turtles cannot survive entirely without men.

  • Schildkröten (Imago/Zuma Press)

    200 turtle babies in one nest

    Female sea turtles return to the beach where they hatched to lay their own eggs again and again. On Raine Island's beach, the largest nesting ground for green sea turtles in the Pacific, you can find up to 18,000 animals during high season. After the eggs have been warmed by sun and sand long enough, the babies hatch, make their way into the sea and only return once it's their time to lay eggs.

  • Korallenriffe Great Barrier Reef in Australien (Imago/ZUMA Press)

    Female surplus across the world?

    Researchers believe there's a lack of male sea turtles across the world. That's why they're examining the effect that rising temperatures have had on green sea turtle populations along the coasts of Hawaii and on the island of Saipan in the western Pacific. The early gender detection method could lead to surprising results there as well.

  • Krokodil (Imago/OceanPhoto)

    Dangerous heat

    The results of the Australian study are bad news for other animals as well. Other reptiles, like crocodiles or lizards, also develop their sex due to temperature. With alligators, things work in exactly the opposite way as they do with sea turtles: If it gets too hot, only male babies hatch from their eggs.


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