Climate change is turning some sea turtle populations 99% female – Technology & Science

About 99 in 100 newly hatched turtle babies are female at one of the biggest sea turtle nesting sites in the world — and warming temperatures are to blame for the lack of male babies, a new study suggests.

That’s because the sex of young sea turtles (and alligators, crocodiles and some other kinds of turtles) is determined by the temperature at which their eggs are incubated, with warmer temperatures producing females, and cooler temperatures producing males.

Because of the role of water temperature in the sex of offspring, scientists have been worried for some time that climate change, which has caused a rapid increase in the average global temperature in recent decades, could push the sex ratios of some populations of those animals to skew female.

A study published Monday in the journal Current Biology shows that’s already happening, and has been for about two decades, at nesting sites at Raine Island and Moulter Cay in the northern Great Barrier Reef “such that virtually no male turtles are now being produced from these nesting beaches.” That area, off the coast of Australia, has experienced very warm temperatures, leading to a range of other problems such as deadly coral bleaching.

The researchers expressed concern that in the future, the lack of males could leave many females unable to find a mate and “eventually impact the overall fertility of females in the population.”

Great Barrier Reef nesting area

That’s a concern because the northern Great Barrier Reef is one of the biggest sea turtle nesting areas in the world, where about 200,000 females go to lay their eggs, reported the scientists from the U.S. National Oceanic and Atmospheric Administration Fisheries Department and the Queensland Department of Environment and Heritage Protection.

A Green Sea turtle swims over a reef near the surf break known as ‘Pipeline’ on the North Shore of Oahu, Hawaii March 20, 2013. (Hugh Gentry/Reuters)

They made the discovery after they caught and examined 400 green sea turtles of various ages feeding off the Howick Group of Islands in the Great Barrier Reef off the coast of Queensland in Australia, studying which were male and which were female. They then used genetic analysis to trace each turtle to the beach where it originally hatched, as the turtles almost always return to lay eggs at the beach where they were born. That means their birthplace can be determined using DNA from their maternal lineage.

Among turtles from the…

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