Down year for nests hints at another surge in 2025
By Steve Plunkett
Following a record-breaking 2023, people who monitor sea turtle nests up and down south Palm Beach County’s coast faced an easier workload this season. And the season, which officially ended Oct. 31, isn’t over yet.
While South County sea turtle nests were down almost 40% this year from the year before — from 4,851 to 2,995 nests for the 14 miles from Boca Raton into Ocean Ridge — those who monitor the marine mamas were not surprised.
Instead of focusing on the decline, “one could also ask: Why such a big year last year?” said David Anderson, who leads Boca Raton’s sea turtle conservation team at Gumbo Limbo Nature Center.
Green sea turtles kept to their usual roller-coaster pattern in digging far fewer nests than the year before.
Boca Raton, for example, had 328 nests by greens in 2023 and only 72 this year, said Anderson.
“They broke their high year/low year pattern the last few years, but since this year was so low, we expect nesting numbers for greens to be high again next year,” Anderson said, referring to their tendency to nest every other year.
Nearby monitors reported similar declines, with greens dropping from 283 to 84 in the southern part of Ocean Ridge, Briny Breezes and Gulf Stream, from 96 to 14 in Delray Beach, and from 530 to 127 in Highland Beach.
“But the very exciting news for us is that we had a very late nester,” Highland Beach monitor Joanne Ryan said.
Volunteers (l-r) Suzie Hiles, Joanne Ryan and Jayne Elder on Nov. 22 monitor and straighten the stakes of the last remaining turtle nest in Highland Beach from the 2024 season. Tim Stepien/The Coastal Star
“After no new nesting since Sept. 3, we thought we were done. But a green turtle decided to come up and nest on Oct. 12, so we will be checking on that nest right into the beginning of December,” she said.
“And funny, but Ocean Ridge had one about a week after us.”
Delray Beach’s season had a more customary finish.
“We documented our last nest on Aug. 23, the last crawl on Sept. 17 and removed the last marked nest from our area on Oct. 16, just in time for the end of daily monitoring on Oct. 31,” said Grace Botson of Ecological Associates Inc., which monitors turtle nests for the city.
A portion of the turtle stakes that Gumbo Limbo Nature Center in Boca Raton uses to mark the nests it monitors. Tim Stepien/The Coastal Star
As for loggerhead turtles, it was “an average year,” Anderson said.
“We finished 2024 with 824 nests, which is about average considering the last five to 10 years of data,” he said. His five miles of beach had 1,038 loggerhead nests in 2023 and 898 nests in 2022.
“Loggerhead nest numbers were declining for decades, bottoming out in 2009 for a lot of beaches. Since 2010, there has been a steady increase (overall) in loggerhead nest numbers,” Anderson said.
Still, as in Boca Raton, the loggerhead totals this year were down from last year’s stellar numbers: from 989 nests to 795 in Highland Beach, from 406 to 292 in Delray Beach, and from 1,051 to 724 in Gulf Stream, Briny Breezes and the south of Ocean Ridge.
Anderson said each year is unpredictable, primarily because loggerheads take 20-plus years to reach sexual maturity, an individual female typically nests every two or three years, and each female deposits anywhere between four and eight nests during the season.
For leatherback sea turtles, the nesting totals were mixed.
“The leatherbacks had a great season,” said Emilie Woodrich, data manager for Sea Turtle Adventures, which monitors the three miles of beach from Gulf Stream into Ocean Ridge. Her group found 19 leatherback nests, up from 15 the year before.
While Highland Beach also saw more, with 13 leatherback nests (up from seven last year), Delray Beach had only 12 leatherback nests (down from 30 last year), and Boca Raton had 19 (down from 28 last year).
“Leatherbacks are critically endangered, so it’s nice to see their nest numbers gradually increasing statewide over the last several decades,” Anderson said.
Overall, this year’s sea turtle nest totals were 827 in Ocean Ridge, Briny Breezes and Gulf Stream, down from 1,377 the year before; 318 in Delray Beach, down from 532 last year; 935 in Highland Beach, down from 1,548; and 915 in Boca Raton, down from 1,394.
The bulldozer-like tracks that a female green sea turtle leaves in the sand will be seen again after the 2025 nesting season begins. Joan Lorne
Declining hatch success
Nest numbers are only part of the story of the survival of these threatened and endangered animals, Anderson noted.
“Not all eggs in sea turtle nests hatch,” Anderson said. “This year, out of over 700 nests inventoried post-hatch, we discovered only 56% of eggs hatched.”
On average, he said, hatch success has declined over the years.
“This can most likely be attributed to climate change. Sand temperature during the two-month incubation period often exceeds the thermal tolerance level of developing embryo.
The eggs cease from developing, resulting in an unhatched egg with a dead embryo inside,” Anderson said.
“In addition to 44% of all eggs not hatching, we lost 49 nests due to storms and high tide events, had 170 nests dug into by predators (most with no damage to eggs), and 88 nests that experienced hatchling disorientation events during hatch-out due to artificial light pollution,” he said.
The moral of the story, Anderson said, “is that total nest numbers can be deceiving.”
“A high number of nests doesn’t mean much when a small percentage of eggs hatch, nests are lost to predators and storms, and hatchlings never make it to the ocean because of light pollution.”
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