Green sea turtle population is 99% female due to rising temperature

Green Sea turtle
A Green Sea turtle swims over a reef on the North Shore of Oahu, Hawaii, in this file photo taken March 20, 2013. REUTERS/Hugh Gentry/

A strange phenomenon is occurring in one population of green sea turtles in Australia’s east coast, where up to 99 percent of the endangered sea turtles that hatch are female. Scientists have determined that the phenomenon, which poses a serious threat to the survival of the species, is linked to the rise in temperature in the region.

The strange findings were published in the scientific journal “Current Biology.” According to the study, 99 percent of the sea turtles that are born in the prime nesting habitat of the Great Barrier Reef have been observed to be female. The reason behind this, scientists discovered, is the rising temperatures in the area.

Unlike humans and many other species that develop into males and females based on sex chromosomes, green sea turtles’ embryos develop sex depending on the temperature outside of the embryo’s egg.

The temperature that is ideal for green sea turtle eggs is 84.74 degrees Fahrenheit. At this temperature, the resulting young turtle population is relatively evenly split between males and females.

However, if the eggs develop in warmer temperatures, the resulting young turtles will more likely to be female. Due to increasing temperatures, almost all of the juvenile turtles that are hatching on Australia’s east coast are female.

Scientists also studied the adult and sub-adult populations of the green sea turtle, and they found out that the stark increase in the female to male ratio in the turtles have been happening for decades. The study found that 99.8 percent of sub-adult turtles are female, while the adult turtle population is composed of 86.8 female turtles.

The results of the study have alarmed scientists and wildlife conservation workers, as the green sea turtle is considered one of the most endangered species in the world, and the Great Barrier Reef is the Pacific Ocean’s largest and most important green sea turtle rookery.

“This is extreme, like capital letters extreme, exclamation point extreme,” says Camryn Allen, a scientist from the National Oceanic and Atmospheric Administration in Hawaii. “We’re talking a handful of males to hundreds and hundreds of females. We were shocked.”