Grant: 16-035R
Project Title: Breeding sex ratios of three imperiled marine turtles nesting in southern FL
Project Manager: Dr. Jeanette Wyneken & Jacob Lasala
Organization: Florida Atlantic University (Research and Educational Institute)
Grant Amount: $9,408.00
Completion Date: 2019-12-05

Summary: Describing key life history behavior is critical to discussing threatened or endangered organisms. Marine turtles are often challenging to access and their mating behavior cannot be directly observed. In this case, one sex (females) can be easily observed during nesting season, but the other sex (males) remains cryptic. Sex ratios, population size and relatedness of individuals are important metrics of population status. Adult sex ratios are primarily determined through census counts of nesting females. This method leaves the number of adult males to be enigmatic. Successful male breeding numbers can be estimated using exclusion paternity analysis (by comparing maternal genotypes to offspring genotypes). We are increasing the accuracy of current adult sex ratio estimates in Florida to add to our understanding of effective population size. In this study we compare the successful breeding sex ratios (the number of males and females contributing to a population) for three imperiled species of sea turtles (loggerheads, greens and leatherbacks) nesting in Florida from 2013-2016. These ratios will be used to assess mating behavior and diversity in these growing populations and refine understanding of management units and population health beyond nest counts. This project is the continuation of a project that was funded last year (final year).

Results: In 2013-2015, the project aimed to identify the breeding sex ratios of marine turtles nesting in Southern FL. To finalize sampling in 2016 we wanted to identify what holes we had left in sampling and to try and solve them. In Juno and in Boca Raton we focused on increasing our sample size of leatherback and green sea turtles and in Sanibel we wanted to identify if mating was occurring between nesting events. To accomplish these two tasks, Jake sampled nesting females from March August 2016 and sampled hatchlings through October. In Juno we sampled: 33 leatherbacks and their nests (431 hatchlings) and due to scheduling issues only 9 green females and their nests (253 hatchlings). We decided to sample more greens in 2017 due to this discrepancy. In Boca Raton, we sampled from 9 leatherback nests (127 hatchlings) and from 18 green sea turtle nests (460 hatchlings). In Sanibel we wanted to look at repeat nesters. The Sanibel Captiva Conservation Foundation revamped their tagging program allowing us to identify more repeat turtles and their nests. We sampled from 15 repeating mothers encompassing 39 nests (625 hatchlings). Together the total number of samples was 1,980. The major issue this year for sampling was storms, we had to relocate 19 nests and that limited our sample sizes for the other nests we could not relocated. To date, all of the Sanibel samples and all of the leatherback samples have been analyzed for genotyping. Jake presented portions of this research at conferences. He gave a well-received talk at the Society for Integrative and Comparative Biology Meeting in New Orleans, LA in January 2017 and a poster at the International Sea Turtle Symposium in Las Vegas, NV, USA in April of 2017. He has given presentations for the general public at Manatee Lagoon in West Palm Beach, FL, the Gumbo Limbo Nature Center in Boca Raton, FL and the Loggerhead Marine-life Center in Juno Beach, FL. The abstracts and the poster are attached. Jake is also currently a part-time docent at Gumbo Limbo Nature Center and talks about the research to all the visitors. Jake also spoke at the 2017 Permit Holders Meeting and presented a number of our findings. The response was very positive and we received many excellent questions about the project. Jake has written a paper that has been accepted pending edits, was featured in the last edition of the Outreach Magazine and is submitting the repeat Sanibel paper in November. Briefly, we did not find that turtles are mating in between nesting events. This confirms long-standing theory of mating behavior, but it had never been studied explicitly. Further, the leatherbacks have continued to stay mostly monogamous, but we hope that we will have a better estimate for the BSR after we complete the tests for the repeat nesters from 2017.