Why do sea turtle nests fail? Modeling clutch loss across the southeastern United States

Abstract

Understanding the relative influence of environmental conditions and disturbance types on species' nest success is imperative to our estimation of current and future population trajectories of vulnerable species, especially ectotherms. The reproductive output of oviparous species is highly dependent on the location of a nest in terms of the environment experienced by incubating embryos and the risk of disturbance events. Climate change may present a particular danger to oviparous species because eggs cannot behaviorally regulate and avoid extreme temperatures. Hierarchical Bayesian models offer a powerful tool for utilizing available long‐term datasets to predict current and future species–environment relations in a manipulatable framework. We modeled the probability of depredation and inundation events occurring during incubation and how these disturbances, along with local climate, predict total clutch failure for loggerhead sea turtles (Caretta caretta) using a dataset of over 9000 nest inventories from five nesting areas that span the latitudinal extent of primary nesting locations in the United States. We found that nesting distance from the high waterline was important in determining the probability of inundation and depredation disturbance events, as well as clutch failure. Nests that experienced at least one inundation event were more likely to have no emergence than nests that experienced at least one depredation event, which may be the result of concerted efforts to control highly destructive nest predators in our study sites or the magnitude of inundation disturbances. Extreme high‐temperature events increased the probability of clutch failure, but the probability of clutch failure decreased with increasing average temperatures up to a critical threshold. The results of these models have clear implications for conservation management decisions on where to deploy predator deterrents and relocate nests, as well as the potential for predicting future changes in nest productivity across the broad nesting range of loggerhead sea turtles.