The Coastal Star

Along the Coast: Green turtles’ pattern accounts for sharp drop in nesting numbers

A hatchling green turtle makes its way into the surf. Green turtles typically nest every other year. Photo provided

By Rich Pollack

At first glance, the dramatic drop in the number of sea turtle nests along the Palm Beach County coastline during the 2018 nesting season appears alarming.
Overall, the number of turtle nests on beaches from Boca Raton to Tequesta dropped about 33 percent — from 39,715 to 26,458 — according to numbers compiled by the Florida Fish and Wildlife Conservation Commission.
Those numbers, however, don’t tell the whole story because they are skewed by an expected drop in the number of green sea turtle nests — with 2018 seeing close to 12,000 fewer green turtle nests than the year before.
Because the pattern for decades has shown that the number of green turtle nests on Florida beaches alternates from extreme lows one year to extreme highs the following year, local turtle researchers are unconcerned by the drop and predict high numbers this year.
“We’re expecting a busy green nesting season,” said David Anderson, sea turtle conservation coordinator for the Gumbo Limbo Nature Center in Boca Raton.
Remove the drop in green sea turtle nests from the equation and it appears the 2018 season did not have a lot of surprises. There were only about 1,300 fewer nests last year in Palm Beach County than in 2017, if you don’t include the green turtle nests.
“If you look at it overall, it was about an average year,” said Kelly Martin, a senior environmental analyst for the Palm Beach County Department of Environmental Resources Management.
Though there were large amounts of sargassum seaweed on the beaches, and some red tides, neither seemed to have much visible impact on nesting or on the number of eggs that hatched in 2018.
Along with the drop in green turtle nests, there was a slight decline in the number of loggerhead turtle nests on county beaches, from 26,245 in 2017 to 24,876 last year. Again, the drop didn’t set off alarm bells, in part because most species of sea turtles nest every two to three years.
“Loggerhead numbers seemed pretty normal,” said Luciano Soares, assistant research scientist for the FWC’s marine turtle program.
There was actually a significant increase in the number of leatherback turtle nests in 2018, with 305 nests compared with 207 in 2017.
In the southern portion of the county, South Palm Beach had an increase in the number of loggerheads, to 1,432 nests in 2018 from 1,352 in 2017. Delray Beach also saw a slight rise, with the number of loggerhead nests increasing from 252 to 271.
Many communities saw increases in leatherback nests, with Boca Raton reporting 18 nests — up from five in 2017 — and Highland Beach reporting seven, up from three the previous year.
In Highland Beach, turtles came ashore to nest 1,825 times, with 955 staying to nest and 870 false crawls. The close to 50-50 ratio is common, according to Barbara James, who coordinates the sea turtle program in the town.
There were some positive signs when it came to hatch rates in 2018 as well.
During an inventory of 645 nests in Highland Beach there was evidence that more than 50,600 hatchlings left their shells, about 75 percent of the overall eggs.
In Boca Raton, the hatch rate was slightly lower at 65 percent, but that was an increase from 58 percent in 2017 and a low of 38 percent in 2016.
Sand temperature and rain, Anderson said, play a large role in those numbers. If the sand is too hot and there’s no rain to cool it down, the egg could be destroyed.
While the hatch rate appeared good in 2018, it’s difficult to know how many hatchlings made it to the ocean or were strong enough to survive once they made it to the water.
Some hatchlings did get caught in the sargassum, Anderson said, with a few rescued by people. Still, some of those young turtles may have used up energy they needed to survive in the ocean while struggling to get past the seaweed.
On its website the FWC says that only about one in 1,000 turtles survives to adulthood, because of predation from birds, crabs and other animals, as well as dehydration if they don’t make it to ocean quickly.
One interesting phenomenon in 2018 was the discovery of sea turtle nests in places that had never seen them before. One Kemp’s ridley nest was discovered as far north as New York.
Could climate change be responsible for a bit of a northern migration, as well as for what seems to be a longer nesting season, which officially begins this month?
That’s a big topic among researchers, who haven’t come to any conclusions yet, local experts say.
Palm Beach County’s Martin points out that the largest concentration of leatherback turtle nests used to be found in Palm Beach County.
Now there are more nests in Martin County than here.
“Climate change could drive turtles to high latitudes,” said Soares, “but not as far north as New York.”
That turtle, researchers say, maybe just got lost.

Sea turtle nesting totals

Boca Raton
2017 – 1,071
2018 – 723
Highland Beach
2017 – 1,829
2018 – 955
Delray Beach
2017 – 304
2018 – 278
Gulf Stream
2017 – 806
2018 – 448
Gulf Stream Park
2017 – 68
2018 – 53
Ocean Ridge (includes Briny Breezes)
2017 – 710
2018 – 638
2017 – 2,013
2018 – 1,071
South Palm Beach
2017 – 1,503
2018 – 1,465
Green turtle nests
2017 – 1,860
2018 – 134

Total nests,
Palm Beach County
2017 – 39,715
2018 – 26,458
Green turtle nests,
2017 – 13,263
2018 – 1,277

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Comment by Sam Lerman on March 1, 2019 at 9:15pm

Great article!

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