Researchers uncover unexpected sea turtle behavior at critical nesting site: 'There is no guarantee that they carry on doing this'

Sea turtles return to the same nesting sites year after year to grow their populations, but rising global temperatures have disrupted this ancient cycle. New research has found that two sea turtle species in Cyprus have gradually shifted instinctual nesting patterns in response to climate shifts.

What's happening?

The new research found that green and loggerhead turtles in Cyprus have reacted to rising global temperatures by returning to their nesting areas earlier and earlier each year. A team of researchers from the University of Exeter and the Society for the Protection of Turtles documented these behavior changes in two separate studies — one published in Endangered Species Research and the other in Proceedings of the Royal Society B.

As a post from the University of Exeter at Phys.org lays out, ocean temperatures determine the sex of sea turtle offspring, "with more females born when it is warmer, as well as fewer successful hatchings when it gets too hot." 

Given this, scientists predict that, by 2100, unless the species moves up its nesting schedule, there will be few if any new loggerhead turtle offspring.

In the report on loggerhead turtles, scientists noted that the animals need to move up their nesting by about 0.5 days each year in order to maintain the species' sex ratio. They need to move up nesting by about 0.7 days each year "to stabilise hatching success."

The team's new data shows that loggerheads have already been moving up their nesting timelines, returning to nest 0.78 days earlier per year since 1993.

As for green turtles, the team found that the species is nesting 6.47 days earlier for each 1-degree Celsius increase in ocean temperature, per the article at Phys.org.

"This is a bit of good news, as we've shown that these turtles are responding to the elevated temperatures brought about by climate change by shifting to cooler months to nest," co-author Annette Broderick said. "There is no guarantee that they carry on doing this though."

Why is it important to understand changes in sea turtle nesting behavior?

The World Wildlife Fund lists green turtles as endangered and loggerhead turtles as vulnerable. Sea turtles are threatened by climate change, including through habitat loss, global temperature increases, and severe storms. Marine pollution like discarded plastics, tangled fishing lines, and oil spills also threaten the animals.

With these populations at such risk, sea turtles need to nest successfully to enable species survival. And while it's good news that turtles have already been adapting their nesting behavior, it's bad news that they must.

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Understanding changes in sea turtle nesting is essential to guiding conservation efforts to protect them. By studying these changes, scientists can develop key strategies to safeguard nesting areas, ensure hatchling survival, and maintain sex-based diversity within sea turtle populations. 

Shifts in sea turtle nesting behavior also highlight the toll of rising global temperatures — and the need to address the human behaviors causing these increases. 

What's being done to mitigate the impacts of rising global temperatures on sea turtles?

While the changing nesting behavior of sea turtles is the species' way of addressing rising temperatures for themselves, researchers are also taking steps to help. 

Scientists continuously track sea turtles to help understand their reactions to climate shifts. Conservationists have also implemented various strategies to protect sea turtle nesting sites, including setting up regulated and monitored areas and broadening public education. Conservation programs to combat habitat destruction, address pollution, and mitigate bycatch also help support sea turtle populations. 

Policies reducing planet-warming pollution benefit sea turtles as well by stabilizing ocean temperatures and preserving their ecosystems. On an individual level — along with taking steps to mitigate your personal contributions to rising temperatures — working to promote healthier oceans and support cleaner recreation areas can also help support sea turtle populations.

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