If record heat doesn’t kill Florida’s baby sea turtles, they still may face birth defects

FORT LAUDERDALE, Fla. — Sea turtles are more susceptible to dying when temperatures hit scorching levels, and now, research from Florida Atlantic University indicates even those sea turtles that do survive are likely to have birth defects.

“It’s sort of a double whammy,” said Sarah Milton, a primary researcher for the study and a professor at FAU’s department of biological sciences. “We have fewer making it out, and the ones that do make it out are less healthy.”

The research revealed a correlation between high temperatures and the success of leatherback sea turtle hatchlings, a vulnerable species.

Vulnerable species are animals facing a risk of extinction but not a risk as high as animals considered threatened or endangered.

“While leatherback turtle nests are laid in the cooler months in South Florida and are deeper than nests of other species, temperatures can still rise surprisingly high,” Milton said, in a statement.

“Increasing temperatures due to climate change poses a significant threat to a species that already has lower nest success than other species that share the same nesting beaches.”

Researchers tracked temperatures in nests along Juno Beach, and they found hatchlings that endured hotter nests had:

• Shorter flippers
• Reduced righting ability, or the ability for the turtles to flip over when placed on their backs
• Shorter incubation periods, which means the time for the turtle embryos to develop was reduced, leading to less time for hatchling development

Worse still, these defects make the turtles much more susceptible to predators, like ghost crabs, Milton said.

This summer set a global record for the highest heat ever measured, which could mean more sizzling nests for leatherback sea turtles in the future.

“Leatherbacks are already slower than other turtles, they are sort of bigger and clumsier and a little bit underdeveloped,” Milton said. “So they already are sort of at a disadvantage and crawling more slowly and being a little bit more clumsy. And so now we’re adding in these higher nest temperatures, it’s making that worse.”

Researchers don’t fully know why high temperatures lead to lower chances of survival and improper development, Milton said.

What researchers do know is even in nests with greater depths or those created earlier in the year in the cooler months, temperatures are still reaching dangerous levels.

“Temperatures are still getting really high, 35, sometimes 36 degrees Celsius, which is basically the temperature where they start to cook at,” she said.

Thirty-six degrees Celsius is almost 97 degrees Fahrenheit.

And the heat affects more than just development — FAU research from about five years ago showed high temperatures lead to more female sea turtles.

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Sea turtle sex is determined by the temperature surrounding the eggs, and only female hatchlings can stand up to the heat.

Male sea turtle populations are already in a decline because of this phenomenon, and Milton said the problem will only worsen with time.

“Pretty much everything we’re seeing coming off of the beaches lately are females,” she said. “It’s going to be hard to find a date on Saturday night in 25 or 30 years from now when (they) are of reproductive age.”

Finding solutions to these heat-spurred problems is challenging, Milton said, primarily because of “the practicality of scale.”

“A lot of times people ask, ‘Well, can’t we just water the nests or can’t we just shade the nests?’” she said. “We can’t shade hundreds and hundreds of nests. … The scale that would be required to hopefully get one male to survive to adulthood would be huge.

“We may be forced to do that at some point in the future, but it’s not the easy solution that people think it is.”

©2023 South Florida Sun Sentinel. Distributed by Tribune Content Agency, LLC.