Sea turtle hatchling success plummets on Sanibel and Captiva following record nest Summer

While 2023 was a record-breaking year with 878 loggerhead sea turtle nests laid on Sanibel and 299 on Captiva, hatchling numbers were the fewest in seven years.

According to the Sanibel-Captiva Conservation Foundation, the reason is partly due to storms, predation, and the hot and dry summer months.

Captiva saw a meager 2,268 sea turtle hatchlings emerge, equivalent to a 10% success rate. While on Sanibel, 24,961 hatchlings emerged, equal to a slightly improved 32% success rate.

“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,” said SCCF Coastal Wildlife Director and Sea Turtle Program Coordinator Kelly Sloan.

June, July and August saw some of the hottest temperatures on record for that time of year, impacting eggs during incubation.

“This excessive heat can kill developing embryos and likely did impact the number of hatchlings produced this summer. Additionally, warm temperatures skew hatchling sex ratios,” Sloan explained.

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Dr. Jeanette Wyneken, a turtle biologist from Florida Atlantic University, said between 87% and 100% of the turtle hatchlings she has tested throughout the last few seasons are female.

“Florida hosts the largest nesting population of loggerheads in the world and limited production of male hatchlings may have serious impacts on future populations,” Sloan said.

The lower numbers SCCF gave were also concerning. About 43% of all nests on Sanibel and Captiva didn’t produce hatchinglings.

Other factors like Hurricane Ian and lesser amounts of inland prey may have also contributed to the number of hatchlings. Hurricane Idalia also played a role in the low turtle hatchling success. Storm surge from Idalia overwhelmed 121 nests and likely flooded others.

Nevertheless, nest predation posed a consequential threat to sea turtles during the 2023 summer.

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

“Record nest counts alone should not be taken as an indication that the population has recovered,” Sloan said. “Ongoing monitoring and research to identify and manage these threats are critical to their success in the future.“

Legitimate improvements to sea turtle conservation have been made over the last few decades, and continue to improve each year. However, it doesn’t deny other growing threats put the already stressed sea turtle population in further peril.