HUTCHINSON ISLAND SOUTH, Fla. — The raised circle of notches in the sand could be mistaken for the beginnings of a castle. But this design is older than the human race, crafted from 110 million years of intuition.
A Hutchinson Island South beachgoer discovered the leatherback sea turtle nest Feb. 6, marking the earliest start to nesting season ever observed in the Sunshine State, according to the Florida Fish and Wildlife Conservation Commission. There’s no telling whether climate change had a hand in the anomaly, but a local marine researcher credits the warming planet with a related phenomenon — determining turtles’ gender.
Jeanette Wyneken used a simple expression to convey the effect of temperature on sea turtle sex: “Hot chicks, cool dudes.” That is, warmer temperatures in underground nests yield more females; cooler nests produce more males.
“There’s been an increase in the number of years that are 100% female hatchling output,” said Wyneken, a professor in the Department of Biological Sciences at Florida Atlantic University in Boca Raton. Wyneken asserted her laboratory is the only in the world to verify sex ratios among sea turtle hatchlings, which she began monitoring in 2002.
“Having that kind of a long-term dataset has allowed us to pick up on this trend,” Wyneken explained, noting the pattern is consistent among the region’s three sea turtle species: leatherback, loggerhead and green.
The leatherback is gargantuan. The endangered species measures up to 9 feet long and weighs as much as 2,000 pounds, making it the largest sea turtle on Earth.
“They’re (leatherbacks) a sea turtle of the open ocean, of deep water, of cool water.”
— Perran Ross, Ph.D., UF
“Leatherbacks are incredibly cool creatures,” said Perran Ross, a scientist in the Department of Wildlife Ecology and Conservation at the University of Florida in Gainesville. “They are the most prodigious deep divers; they dive down hundreds of meters.”
The prehistoric reptiles also practice extensive migration, swimming as far north as Canada and south as Argentina, according to the U.S. Fish and Wildlife Service.
“They’re a really different sea turtle. They’re a sea turtle of the open ocean, of deep water, of cool water,” Ross said. “No other sea turtle has anything like their metabolic adaptations.”
Leatherbacks’ ability to withstand such temperature variation gives Ross confidence the species will prove resilient amid climate change. It’s also why he disagrees with the ramifications of Wyneken’s findings.
If warmer temperatures continue to breed an increase in female turtles, “we’re going to have an issue with genetic diversity in the population, and then low production of eggs,” Wyneken said.
Ross suggested evolution will even out the male-female ratio long term.
“Stick a thermometer in 100 turtle nests,” he said. “They already face a higher degree of temperature variation than is postulated to be caused by climate change.”
The pair concur on this: Sea turtle nesting patterns are a natural mystery dependent on so many factors it’s impossible to attribute this month’s record-breaking nest to global warming.
Still, Ross stressed he’s not unconcerned about the reptiles’ fate in a shifting environment.
“Am I worried about sea turtles and climate change?” he asked. “Damn right I am.”
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This article was written for Lindsey Leake’s 491.701 Communicating Climate Change course at the Johns Hopkins University Krieger School of Arts and Sciences on Feb. 25, 2020.