Most sea turtles now female in north Great Barrier Reef

January 8, 2018
Credit: CC0 Public Domain

The vast majority of green sea turtles in the northern Great Barrier Reef are now female because of warmer temperatures due to climate change, which influences their sex during incubation, researchers said Monday.

The population of about 200,000 nesting females in the area along the east coast of Queensland, Australia, is one of the largest in the world, and could crash without more males, according to the report in the journal Current Biology.

The temperature at which eggs incubate determines the sex of the eggs. Warmer nests, which are dug into beaches, mean more females. Just a few degrees can mean the difference between a balanced and skewed sex ratio.

"With average global temperature predicted to increase 4.7 Fahrenheit (2.6 Celsius) by 2100, many are in danger of high egg mortality and female-only offspring production," said the report.

Since figuring out the sex of buried is too difficult, researchers decided to catch sea turtles and use genetic tests to find out where they'd come from.

They worked in an area where two different populations of green sea turtles (Chelonia mydas) forage—one from a warmer area and the other from a cooler area.

After collecting 411 for analysis and release, they found a "moderate female sex bias" in turtles from beaches in the cooler, southern Great Barrier Reef, where about 65-69 percent were female.

But those in the warmer, northern Great Barrier Reef were "extremely female-biased," at 99.1 percent female among juveniles and 99.8 percent for those between juveniles and adults.

A total of 86.8 percent of adult-sized turtles from the area were female.

The trend of producing more females in warm areas has been ongoing for more than two decades, according to lead author Michael Jensen, from the US National Oceanic and Atmospheric Administration.

The study "provides a new understanding of what these populations are dealing with," he said.

"Knowing what the sex ratios in the adult breeding are today and what they might look like five, 10 and 20 years from now when these young turtles grow up and become adults is going to be incredibly valuable."

Experts say there are strategies that could help, including erecting shady tents over beaches where turtles nest to keep them cool.

Green sea are considered endangered throughout much of the world, under siege from coastal debris, loss of habitat, fishing nets and pollution, according to the International Union for Conservation of Nature.

Explore further: Warming temperatures threaten sea turtles

More information: Michael P. Jensen et al, Environmental Warming and Feminization of One of the Largest Sea Turtle Populations in the World, Current Biology (2018). DOI: 10.1016/j.cub.2017.11.057 , … 0960-9822(17)31539-7

Related Stories

Warming temperatures threaten sea turtles

June 21, 2017

The study by Dr Jacques-Olivier Laloë of the University's College of Science and published in the Global Change Biology journal, argues that warmer temperatures associated with climate change could lead to higher numbers ...

'Heat-proof' eggs help turtles cope with hot beaches

September 26, 2011

( -- Sea turtles face an uncertain future as a warming climate threatens to reduce their reproductive viability. However, new research led by the University of Exeter and published this week in Proceedings of ...

Green sea turtles recover in Florida, Mexico

March 20, 2015

Long considered an endangered species, green sea turtles in Florida and Mexico have bounced back and officials said Friday they are seeking to change the turtles' protected status to "threatened."

Recommended for you

How plants bind their green pigment chlorophyll

October 19, 2018

Chlorophyll is the pigment used by all plants for photosynthesis. There are two versions, chlorophyll a and chlorophyll b. These are structurally very similar to one another but have different colors, blue-green and yellowish ...


Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.