Sea Turtle Hatchling Count Lowest Since 2016 Despite Record Nesting Season

by The Sanibel Captiva Conservation Foundation

Sea turtle hatchling count is lowest since 2016 despite a record nesting season. SCCF photo

If you walked along the beaches of Sanibel and Captiva this summer, you likely saw more marked sea turtle nests than ever before. This year was a record-breaking season for the total number of loggerhead nests laid on our beaches, with 878 nests laid on Sanibel and 299 laid on Captiva.

“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.

The islands’ hatchling counts were the lowest recorded since 2016, due in part to storms, predation, and the hot and dry summer we experienced. Hatch success on Captiva was alarmingly low — around 10 percent (2,268 hatchlings emerged). Sanibel’s hatch success was slightly higher at 32 percent (24,961 hatchlings emerged).

This past June, July, and August were also the hottest on record globally, meaning the nests incubating during those months experienced warmer temperatures than ever before.

“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.

According to sea turtle biologist Dr. Jeanette Wyneken of Florida Atlantic University, between 87 percent and 100 percent of the hatchlings she has tested over the last few seasons have been 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.

A deperdated sea turtle nest. SCCF photo

Predation by coyotes was also a significant concern this season.

Approximately 43 percent of the nests on Sanibel and Captiva were depredated, exceeding the recommended threshold of 10% outlined by the Loggerhead Recovery Plan.

While this could be a result of implications from Hurricane Ian, such as reduced inland prey and less human activity on the beach to scare coyotes off, nest predation posed a consequential threat to sea turtles this summer.

Another event that contributed to the low hatch success was tropical storm Idalia, which impacted our beaches at the end of August, when a large percentage of nests were still incubating. The surge associated with the storm washed away 121 nests and likely caused water inundation, or flooding, in many others.

“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.

Great strides have been made in sea turtle conservation over the last several decades, but emerging and worsening threats continue to impact these already stressed populations.

“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.“

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