Factors Influencing Loggerhead (Caretta caretta) and Green Turtle (Chelonia mydas) Reproductive Success on a Mixed Use Beach in Florida

Abstract

Abstract Although estimates of sea turtle reproductive success are important to quantify population status and effects from threats, published representative values of these rates are rare. Most assessments involving hatching success have taken place as part of experimental analyses that did not spatiotemporally represent a population. To fill this gap, we analyzed an 11-yr time series (2004–2014) of sea turtle hatching and emergence success data for a 7-km stretch of Florida beach backed by mixed suburban and resort/recreational land use. Our analysis examined potential egg-mortality factors associated with the incubation of these nests. The data set included representative sampling of loggerhead (Caretta caretta) nests (n = 2,543, 34.4% of all nests made during the period) and green turtle (Chelonia mydas) nests (n = 972, 44.7% of all nests). Mean (± SD) annual hatching success was 68.6% ± 35.5% for loggerheads and 59.6% ±  39.5% for green turtles, and mean emergence success was 66.6% ± 35.7% for loggerheads and 57.0% ± 39.1% for green turtles. Mammalian predation rates had little effect on overall hatching success trends on our study beach with the sample of predation events (0.3% over 11 yrs) too small to analyze. There were significant effects from tropical storms and hurricanes on hatching success trends throughout the study period, based on negative correlations between hatching success for each species and highest wave height incurred during incubation, mean wave height during incubation, and the number of days that study nests incurred 2 m or higher waves. Hatching and emergence success for each species were lowest during tropical cyclones, which corresponded with an increased number of complete nest wash-outs. Nests within our study site had higher hatching and emergence success rates compared with loggerhead and green turtle nests at other Florida beaches. These assessments of reproductive success are part of a conservation program undertaken at an actively used resort beach, with conservation actions that included vigilance for nest mortality factors and outreach to beachgoers with the aim to promote conscientious behavior during the sea turtle nesting season.