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Promising start to sea turtle nesting season in ends in disappointment

A sea turtle under water.
Sanibel-Captiva Conservation Foundation
Despite a record number of sea turtle nests on Florida beaches in 2023, remaining shoreline damage from 2022’s Hurricane Ian, overwashed beaches from 2023's Hurricane Idalia, and record-setting high temperatures on land and in the ocean last summer combined to turn a promising start to the nesting season into a bleak reproductive cycle in Southwest Florida

Imagine the surprise felt by sea turtle lovers when the number of egg-filled clutches laid on Southwest Florida beaches during last summer’s nesting season totaled a normal year despite shorelines transformed by Hurricane Ian.

Even better: The mommas kept coming.

Female sea turtles often return to the beach of their birth to nest every three years or so, which made understandable the fears of the large and active cadre of turtle volunteers that Category 5 Ian in September 2022 had rendered nesting beaches so unrecognizable the females would be lost, search aimlessly, then dump their eggs at sea.

But more than 200,000 sea turtle nests were counted around Florida last summer, nearly doubling the annual averages a decade ago. Loggerhead and green turtle nests set single-season records. And despite the 2023 nesting season ending on Oct. 31, nests were still hatching.

A marked sea turtle nest with the metal grating that helps deter predators like coyotes and raccoons from eating the turtle eggs
University of Florida
A marked sea turtle nest with the metal grating that helps deter predators like coyotes and raccoons from eating the turtle eggs

In Southwest Florida, loggerheads laid 878 nests on Sanibel Island and 299 on Captiva Island, also records. Bonita Beach had 151 nests. Big Hickory Island had 22 nests.

On Fort Myers Beach, which Hurricane Ian covered with up to 18 feet of storm surge for hours in 2022, and where ever since beach builders have been restocking sand in dunes and berms, sea turtles laid 71 nests.

“Fortunately, Fort Myers Beach has a berm that was constructed this past season, and the turtles laid their nests in that berm,” Eve Haverfield, director of Turtle Time, a volunteer group that monitors nests along Fort Myers Beach and points south. “Those nests were very, very successful.”

It turned out that the berm on Fort Myers Beach would be one of the few places in Southwest Florida where turtle hatchlings had it so easy.

The record-setting start to 2023’s nesting season was real, but any notion that it would translate into a bumper crop of hatchlings was dispelled by extreme weather events linked to climate change ending in a sad and bleak reproductive cycle.

"While we should be encouraged by these impressive nest numbers ... they only tell half the story"
Kelly Sloan, Sanibel-Captiva Conservation Foundation's sea turtle coordinator

Last year’s record-setting heat is mostly to blame. Warmer-than-normal oceans fueled Hurricane Idalia’s rapid growth, and high surf from the storm’s blowby buried nests under six feet of sand. It was so hot on the beaches other nests never cooled down, even during nighttime, which is a hatchling’s cue to emerge and start hustling toward the moon-lit ocean. Instead, the baby turtles died in their eggs.

“We had several nests that basically baked,” said Haverfield, who has been a turtle volunteer for more than 30 years. “We did not have a great season.”

Nests half the story

On Sanibel and Captiva islands hatchling counts were the lowest since 2016 despite the Sanibel-Captiva Conservation Foundation reporting that the 2023 season also broke nesting records.

“While we should be encouraged by these impressive nest numbers and proud of the ongoing conservation efforts leading up to this point, they only tell half the story,” Kelly Sloan, SCCF’s sea turtle coordinator, said. “Record nest counts alone should not be taken as an indication that the population has recovered.”

The SCCF found the seven-year low in hatchling success was also due to heat-related deaths, as well as other factors including surging waves from Idalia, which washed away 121 nests and likely flooding many others.

Coyotes, undeterred by the metal cages usually placed over nests but missing since Hurricane Ian, and undisturbed by fewer people on the hot beaches at night, ransacked the nests.

“In addition to these threats to embryos, the hatchlings that did emerge experienced more light pollution than in the past,” Sloan said. “We documented our highest number of disoriented nests in a single season.

Sloan said the hatch rate on Captiva Island was very low at around 10% of the total nests, or about 2,268 hatchlings. Sanibel Island’s hatch success was slightly higher at 32%, or about 24,961 hatchlings.

Now what?

Jack Brzoza, a sea turtle biologist with SCCF, is one of those who figures out the numbers — and tries to find a silver lining.

“We wait a couple of days to inventory a nest to allow any remaining sea turtle hatchlings to emerge before removing or counting eggs,” he said.

 After a coyote made a meal out of this sea turtle nest, volunteers with the Sanibel-Captiva Conservation Foundation inventory the ransacked hole for future reference
After a coyote made a meal out of this sea turtle nest, volunteers with the Sanibel-Captiva Conservation Foundation inventory the ransacked hole for future reference

The number of eggs in the nest is counted. The proportion that hatched represents the nest’s “hatch success,” while the proportion of hatchlings that made their way out of the nest to the ocean represents “emergence success.”

Nests that never hatch, or were never observed to have hatched but reached their full incubation period, are also counted.

After the inventory, the eggs are replaced in their natural state under the sand to be returned to the natural rhythms of life and death of hatchlings.

“This maintains the natural process and, most importantly, contributes to nutrient cycling within the coastal ecosystem,” Brzoza said. “Remaining materials from sea turtle nests supply a host of nutrients to the beach, which can be taken up by dune vegetation and various wildlife.”

Environmental reporting for WGCU is funded in part by VoLo Foundation, a non-profit with a mission to accelerate change and global impact by supporting science-based climate solutions, enhancing education, and improving health.

WGCU is your trusted source for news and information in Southwest Florida. We are a nonprofit public service, and your support is more critical than ever. Keep public media strong and donate now. Thank you.

Copyright 2024 WGCU. To see more, visit WGCU.

Tom Bayles
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