Date

Summer 2024

Document Type

Master's Thesis (Open Access)

Degree Name

Master of Science (M.S.)

Department

Moss Landing Marine Laboratories

Abstract

Understanding the spatial ecology of highly migratory marine animals is essential for effective conservation strategies, particularly in the face of climate change and increasing anthropogenic pressures. This study investigates the nesting characteristics, habitat use, and behavior of leatherback sea turtles (Dermochelys coriacea) in the Northwest Atlantic population nesting at Sandy Point National Wildlife Refuge (SPNWR) in St. Croix, US Virgin Islands.

Ten female leatherbacks were studied during the internesting interval of the 2020 and 2021 nesting seasons. The study’s objectives were to examine leatherback nesting characteristics, delineate critical internesting habitats, and characterize behaviors during the internesting interval. Data collection included a combination of nighttime beach surveys (direct observation) and deployment of Argos satellite-transmitting dataloggers (satellite tags), alongside analysis methods such as Autocorrelated Kernel Density Estimation (AKDE) and movement persistence models.

The average internesting tracking duration was 26 days, and during the internesting interval turtles traveled far offshore of SPNWR. Home range analysis revealed that critical habitats for leatherbacks during the internesting interval extend beyond the waters of existing Critical Habitat areas, and throughout the waters surrounding and between St. Croix, Puerto Rico, and Antigua. Behavioral analysis showed that leatherbacks consistently exhibited high move persistence, indicative of rapid and directed movement, potentially in response to predator risk. These home range and behavioral results highlight the importance of considering broader spatial scales for conservation efforts and of understanding predator-prey dynamics.

Reproductive output by leatherbacks in the study was relatively low compared to historic data. Leatherbacks nesting at SPNWR exhibited reduced reproductive philopatry, with 20% of turtles exhibiting straying behavior and nesting on multiple beaches besides Sandy Point including Vieques, Puerto Rico, Antigua, and the east side of St. Croix. This finding challenges the traditional view of leatherback fidelity and indicates potential adaptability to environmental changes. The analysis also highlighted instances of extended internesting intervals (up to 25 days), demonstrating that leatherbacks may skip a nesting event during the season and suggesting a shift in reproductive strategies, potentially linked to environmental stressors or changes in foraging opportunities. The average clutch frequency was 3.6 (± 1.9 nests). These reduced clutch frequencies and overall reproductive outputs compared to historical data indicate possible shifts in life history traits under changing climatic conditions.

The findings of this study enhance our understanding of the nesting and internesting behaviors of leatherback sea turtles. They highlight the importance of updating and refining conservation strategies to reflect these nuanced behaviors. The study suggests a need for expanded critical habitat protections, increased regional collaboration, and further investigation into leatherback-predator interactions. These insights contribute to a comprehensive understanding of the leatherback sea turtles' adaptive strategies to environmental challenges at Sandy Point, underlining their resilience and dynamic ecological roles.

Download

Share

COinS