The Role of Sand Moisture in Shaping Loggerhead Sea Turtle (Caretta Caretta) Neonate Growth in Southeast Florida

Abstract

Many environmental variables that affect incubating turtle eggs in the nest may also affect hatchling development, following hatchling emergence. However, these effects may be subtle and are largely unexamined. In this study, we analyzed the effect of sand moisture content during incubation on the postemergence growth rates of loggerhead sea turtles (Caretta caretta) in southeastern Florida. We divided 10 clutches in halves, reburied them, and exposed them to 1 of 2 treatments. At emergence, 7 clutches met minimum criteria for inclusion in the study. One halfclutch received only ambient rainfall (“dry” treatment) while the other half-clutch received ambient rainfall plus daily watering (“wet” treatment). Data loggers were used to record incubation temperatures in both groups. Hatchlings were captured at emergence and laboratoryreared over a period of ∼ 3 mo. Mass, straight carapace length (SCL), and straight carapace width (SCW) were measured weekly to track growth. Initial measurements were larger for turtles from the wet nests in all metrics. Turtles from wet nests grew more in SCW than turtles from dry nests. Turtle growth from the 2 treatments did not differ in SCL or mass measurements. Larger initial sizes and faster SCW growth may enable the turtles to more quickly achieve a refuge size from their gape-limited predators. Moisture availability during nesting season is projected to decrease based on climate change models. If that change materializes, it could negatively affect hatchling sizes and neonate growth rates, survival, and hence the recovery of this imperiled species.