As intense heat waves become more commonplace across the US, researchers fear more volatile temperatures will stunt sea turtle populations.
In the Florida Keys, Bette Zircklebach, who directs the Turtle Hospital in Marathon, is worried about the species’ fate, saying that in the past four years, researchers have only found female eggs and hatchlings just as the state has seen temperatures touch record highs.
Even though sea turtles are hatching, climate change bodes poorly for population dynamics. With few males mating with most of the females, genetic diversity decreases, which can prohibit successful breeding sessions and could mean that men pass on weak genes to an unknown number of offspring.
For turtles, who lay their eggs in nests dug into coastal sand, gender is temperature dependent, according to the National Ocean Service.
If a turtle’s eggs incubate below 81.86℉, they will come out as male. If eggs incubate at temperatures higher than 88.8℉, they will hatch as females. Temperatures that fluctuate between the extremes will produce a mix of both male and females, a mix that is necessary for turtles to keep reproducing and surviving.
But the heat is not just exclusive to Florida’s coast as it has also crept up to North Carolina, where researchers are just beginning to see changes in male sea turtle populations.
“This pattern has been seen in Florida for quite some time because it's hot in Florida and North Carolina is at a higher latitude, and so we tended to in the past have a more balanced sex ratio,” said Dr. Stephanie Kamel, an ecology professor at the University of North Carolina Wilmington.
Over the past 25 years, according to Kamel, the Tar Heel State has seen a sharp decline in the production of male hatchlings, with males making up less than 10% of hatchlings in 2015, compared to 50% in 1991.
“2015 is a long time ago now, right?” said Kamel. “So you can project four from 2015 to 2022, and that pattern [is] not changing.”
The National Ocean Service also warns that with warmer weather comes warmer sand, which could create “lethal” incubation conditions for the physiological health of sea turtles and other reptiles.
Zircklebach warned that there is an increasing number of sea turtles battling fibropapillomatosis, a disease that causes tumors to grow on turtles in warmer waters in and around developed land.
Local wildlife resource departments should protect vulnerable sea turtles by implementing management plans for nests, said Kamel.
That includes cordoning off certain areas of beaches and coastlines to build shades over nests so that eggs can hatch at lower temperatures. Yet much remains unknown for researchers tasked with protecting and defending the species, which has a life span of up to several decades.
“There’s just so much that we don't know,” said Kamel. “It’s really hard to study a sea turtle just given their life history, right? They’re slow to grow, they’re endangered, they go offshore, then you can’t find them again for years and years and years.”