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Author ORCID Identifier

https://orcid.org/0000-0002-8560-0683

Document Type

Open Access Dissertation

Degree Name

Doctor of Philosophy (PhD)

Degree Program

Environmental Conservation

Year Degree Awarded

2019

Month Degree Awarded

September

First Advisor

Andy Danylchuk

Subject Categories

Marine Biology

Abstract

Considering many sea turtle populations are a fraction of their historic size and anthropogenic threats within the marine environment are increasing, additional data are imperative to help mitigate anthropogenic disturbances and to build resilience into sea turtle populations. In this dissertation, I present three data chapters focused on immature sea turtle ecology and conservation. These chapters evaluate sea turtle ecology and conservation at varying scales, ranging from mitigating human-wildlife interactions at the individual level, to coastal movements and space use at the ecosystem level, and to large scale climate change impacts at the population level. Ultimately, these chapters provide a better understanding of immature turtle behavioral and spatial ecology within nearshore waters that are required for the continued conservation of turtles and their habitats.

In Chapter 2, following Chapter 1: General Introduction, I quantified the behavioral response of immature green turtles (Chelonia mydas) to disturbance by snorkelers in a popular ecotourism venture on Culebra Island, Puerto Rico, United States. Using a standardized disturbance stimulus, I evaluated whether turtles have individual-level responses to snorkeler disturbance. I found ninety percent of turtles disturbed by snorkelers initiated their fights at distances of 3 m or less. Thus, I recommended snorkelers remain greater than 3 m distance from immature turtles. In addition, I found a significant intra-individual repeatability in behavioral responses to disturbance, suggesting, ecotourism activities may be disproportionally affecting individual turtles depending on their personality type. Finally, I suggest ecotourism activities be temporally and spatially stratified and better regulated to reduce missed foraging opportunities by immature turtles in important foraging areas.

In Chapter 3, I used acoustic telemetry to describe movement patterns and connectivity of immature green turtles on Culebra and Culebrita Islands, Puerto Rico and, secondly, to determine the spatial-temporal drivers of presence and absence of turtles. Network analysis revealed high fidelity within bays with little to no connectivity across the islands. Based on these findings, I provided evidence that habitat quality and availability in combination with predation risk (innate or learned) is likely driving different rates of somatic growth across the island. Using a presence-absence Bayesian model, results indicated turtles occupied areas of lagoon and seagrass habitats at night, and were rarely using areas of macroalgae habitat. The parameter estimates from the model enabled me to predict diel movement patterns and space use across the focal bay. While habitatswithin Culebraare still largely intact, coastal embayments are becoming increasingly threatened. Given that my research showed that turtles in Culebra exhibit high fidelity within the bays, it is imperative to protect these distinct habitats that serve as both shelter and foraging areas.

In Chapter 4, I examined the oceanic, atmospheric, and biological factors that may affect the increasing trend of cold-stunned immature Kemp’s ridleys (Lepidochelys kempii) in Cape Cod Bay, Massachusetts, United States. Using cold-stunned data collected since the early 1980’s and analytical methods, such as machine learning algorithms and Bayesian modeling, I demonstrated higher cold-stunning years occurred when the Gulf of Maine has warmer seas surface temperature (SST) in late October through early-November. Hatchling numbers, a proxy for population abundance, was not identified as an important factor in predicting the number of annual cold-stunning strandings. Further, I predicted the potential annual cold-stunning counts out to 2031 based on the increasing Gulf of Maine SSTs and evaluated the population level effects of future cold-stunning events in the face of climate change. While cold-stunning at the population level may be minimal, I recommend the continued efforts to rehabilitate cold-stunned turtles to maintain population resilience for this critically endangered species.

For the fifth, and final chapter, I synthesized these findings in the context of contributions to the greater field of sea turtle conservation and management, propose future research directions, and re-visit caveats of these studies. Within this chapter, each data chapter is revisited to provide direct conservation applications to help mitigate anthropogenic disturbances. In Chapter 2, I suggest alternate ecotourism regulations and advocate for the spatial-temporal stratification of green turtle snorkel tours. In Chapter 3, I highlight the differential space use of green turtles within coastal habitats and advocate for the importance and protection of these habitats to ensure recruitment into adult populations. And finally, in Chapter 4, I advise for the recovery and rehabilitation of cold-stunned Kemp’s ridley turtles to provide population resilience for this critically endangered species in a changing world.

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