Cool way to solve turtle sex dilemma

A SIMPLE intervention to cool turtle nests could help stave off a growing crisis in the sex ratios of global turtle populations caused by climate change, according to newly published research led by a Welsh university scientist.

The sex of turtle hatchlings is determined by the temperature at which the eggs incubate, and as global temperatures rise vastly more females than males are hatching, putting their future in jeopardy.

Many turtle populations are now showing evidence of a female sex bias, the green turtles in particular are facing disaster with 99% of all eggs in some regions hatching female.

But research among loggerhead turtles on the island of Boa Vista, part of the Cape Verde archipelago off the west coast of Africa, has found that a cheap intervention to cool nests could be a means of stabilising populations.

The study found that in natural nests on the island 69% of all hatchlings are female, with this figure expected to rise to up to 95% in the coming years as global warming impacts the temperature of the sand.

There were an average of 92 eggs in a loggerhead turtle clutch, the research found.

But by halving the number of eggs in a clutch scientists found they could lower nest temperatures by reducing the amount of metabolic heat, the heat generated by the hatchlings developing, by 0.5°C, resulting in just 45% female hatchlings.

Shading the nests, where dark fabric was suspended 15cm above the clutch, had an even more dramatic effect, reducing average temperatures by 1.1°C and producing just 1.46% females on average.

Dr Leo Clarke, a marine biologist at the University of Bangor and lead author of the study, said: “Every night we would trek up and down the beach and there would be female turtles coming ashore to dig their nests and laying their eggs.”

He explained: “Once they begin to lay their eggs they are in a sort of catatonic state, a bit of a trance, and you can collect the eggs as they lay them.”

The eggs were transferred to a fenced-off hatchery on the beach run by a local conservation programme to protect them from predators such as birds and crabs.

A data logger placed in each nest, which were all buried to a depth of 45cm, recorded the temperature every 15 seconds throughout incubation.