Knowledge of the sex ratio of a population is crucial to understand their structure and dynamics. For species, such as marine turtles, with temperature-dependent sex determination, this knowledge provides a baseline in advance of climate change. Determining the primary sex ratio for marine turtle populations is challenging since offspring lack sexually dimorphic external characteristics. Therefore several proxies have been used to estimate the primary sex ratio of marine turtle populations. However, no study to date has compared estimations of sex ratio when using different proxies to determine the most accurate and to detect potential bias. To address this, we estimated the sex ratio of natural loggerhead, Caretta caretta, nests using 8 different proxies: two based on constant temperature equivalent (average of temperature or average temperature weighted by the growth of embryos during each time step) both for three developmental periods (the whole incubation, the middle third of incubation and the middle third of development) as well as two proxies based on incubation duration (duration of the whole incubation and of the middle third of development). Sex ratio estimates differed greatly depending on the proxy being used. Here we discuss the differences among proxies based on the biological relevance of underlying hypotheses and highlight the need for studies to accurately determine the thermosensitive period and to obtain appropriate estimates of embryo growth rate to estimate marine turtle sex ratio.

Full Reference: ​Fuentes, M. M. P. B., Monsinhon, J., Lopez, M., Lara, P., Santos, A., Marcovaldi, M. A. G., & Girondot, M. (2017). Sex ratio estimates for species with temperature-dependent sex determination differ according to the proxy used. Ecological Modelling. 365, 55-67

                    This summer, Florida State University (FSU), the Department of Environmental Protection, and the Florida Fish & Wildlife Conservation Commission / Research Institute (FWC/FWRI) collaborated to form a sea turtle internship at T.H. Stone Memorial Saint Joseph Peninsula State Park.  The goal of this internship was to assist park staff with sea turtle patrol at a more remote, dynamic, and less developed area of the park, the Wildrness Preserve.  The four FSU interns included undergraduates Sophia Fonseca, Emma Guss, Elizabeth Thomas, and John Zito.  Graduate student Natalie Montero is conducting her research at the park and acted as the on-site supervisor for the internship.  These students are a part of the Marine Turtle Research, Ecology, and Conservation Group, which is led by FSU Professor Dr. Mariana Fuentes.
                An average day began hours before the sun rose, arriving at the park at around 5:30am every day.  They drove a Utility Task Vehicle (UTV) to the tip of St. Joseph’s Peninsula, dropping off half the group to the start of Section A, and the other half driving to the beginning of Section B.  The unpredictable amount of erosion occurring on the peninsula this time of year allows for the UTV to be ridden on the inland trail only and not the beach.  The group walked almost five miles of beach each day, which totaled over 1300 miles combined for the summer.
Every morning’s main objective was to find sea turtle crawls and determine whether a nest had been laid.  This was completed on FWC sea turtle crawl data sheets and entered in a notebook and spreadsheet containing the entire season’s crawls.  If a crawl was identified to be a nest, it was surrounded by three wooden stakes, one of which had a yellow nesting sign attached to it.  Other data collected included date, species of sea turtle, and location pertaining to high tide line as well as latitude and longitude.
            Natalie Montero is researching the effects of local climate and nest environment on hatchlings and used select nests at St. Joseph for her studies.  This included locating the egg clutch, depositing a temperature logger into the nest, collecting a sand sample from the surface of the nest, and increasing protection of the turtle nest with the addition of a self-releasing screen.  She is also conducting this study at St. George Island State Park to compare how nests laid and hatchlings born at these two locations may differ.
            The total amount of beach covered by the group lent itself to 96 sea turtle nests, 89 of which were loggerhead sea turtle nests and seven were green sea turtle nests.  Unfortunately, this park experiences high predation by nonnative coyotes and native ghost crabs. After the completion of the internship, 66% of all nests monitored had been predated by coyotes, ghost crabs, or both. However, the group is keeping their hopes up for the untouched nests!