Sea turtles change nesting methods to cope with climate change

Researchers who have been monitoring green and loggerhead turtles nesting in Cyprus have found that they are returning to their nesting sites earlier each year to avoid rising temperatures.

For sea turtles, temperature determines the biological sex of their hatchlings, with more females being born when it’s warmer, and fewer hatchlings successfully when it’s too hot. Turtles also “reproductive cruising,” meaning they return to nest in the area where they were born.

Using three decades of data, a team from the University of Exeter and the Turtle Conservation Society predicts that by 2100 there will be virtually no loggerhead turtles born, unless they counteract higher temperatures by accelerating their nesting season.

After placing temperature loggers in nests at night when female turtles lay eggs and retrieving eggs after nests hatched, the researchers estimated that turtles would need to nest 0.5 days earlier each year to maintain current sex ratios and 0.7 days earlier each year to avoid unsuccessful hatching.

However, the researchers' data shows that loggerhead turtles have actually been nesting earlier in the year, with females returning to nest 0.78 days earlier each year since 1993. This means that, at least for now, turtles are doing enough to ensure their eggs continue to hatch by nesting earlier at more ideal temperatures.

The team also published a study using 31 years of data on more than 600 individual green turtles nesting at the same beach in Northern Cyprus to see what factors influence when they start laying eggs each year, and how we can explain the progress we've seen over the past three decades.