Sea Turtle Monitoring and Research Updates
Most sea turtle nesting has concluded on Sanibel and Captiva Islands, but hatchlings continue to emerge. So far, the SCCF sea turtle team has documented 31,255 emerged sea turtle hatchlings on our beaches in 2022.
Most recent nest counts include 766 loggerhead sea turtle (Caretta caretta) and 18 green sea turtle (Chelonia mydas) nests on the islands. Our team and volunteers have inventoried 578 of these nests.
In addition to monitoring and educating the public about sea turtles, SCCF staff are also investigating differences in sea turtle hatch success on Sanibel versus Captiva beaches, as annual hatch success (the proportion of eggs producing live hatchlings) on Captiva tends to be considerably lower than on Sanibel.
“There are some historic differences in the sand between the two islands, and we wanted to try to tease out potential impacts on sea turtle reproductive output,” said Kelly Sloan, SCCF coastal wildlife director and sea turtle program coordinator. “This multiyear project is taking a deeper look into how several physical properties of the incubation environment may interact to impact embryonic development and ultimately hatch success.”
Much of the field work for this year’s research has been possible thanks to Research Technician Jacob Wozny, whose position at SCCF is 100% funded by a grant through Florida Sea Turtle Specialty License Plate Sea Turtle Grants Program.
For this work, Wozny installs probes in each research nest to record the temperature, moisture, and groundwater level every 15 minutes throughout incubation to evaluate how these variables vary across the beaches. This has been done for 60 nests this summer.
“We’re also taking sand samples to measure grain size, compaction, color, and bulk density, and calculating beach elevation, width, and slope,” Wozny said.
Analysis from research nests studied in 2021 suggested that sand is coarser and nest exposure to groundwater is more likely on Captiva than Sanibel, but conditions will likely be different this year due to the recent addition of nonnative sand to Captiva, Sloan said. The team will also be examining the contents of unhatched eggs from each research nest to determine the developmental stage at mortality and identify potential causes of mortality.
”After this season, we will be able to evaluate how the incubation environment may have changed after Captiva’s beach renourishment project. Our data will provide valuable insight into local conditions, with implications concerning future generations of sea turtles,” Sloan said. “Hopefully, our results can help inform future beach management.”
Other SCCF staff involved in this study include Sea Turtle Biologist Jack Brzoza, Wildlife Biologist Mike Mills, and Research Technician Megan Reed (2021 season).