Conservation and management of rare species

Abstract

Conservation and management of rare species is one of the most challenging tasks confronting natural resource managers. Species are classified as rare for several reasons: (1) very few individuals are known to exist, (2) the species is widely distributed resulting in low densities, (3) the species has a clumped distribution and/or (4) the species has very low detection rates (elusive behavior, difficult to catch/observe). They are often most negatively affected by environmental perturbation (more specifically human alterations) making conservation and management extremely challenging. The Ivory-billed Woodpecker (Campephilus principalis), if extant (Fitzpatrick et al. 2005; Hill et al. 2006; Jackson 2006), may be the most rare and elusive bird species in the United States and thus presents a great challenge for designing efficient and effective surveys. In this dissertation I present results from a large-scale effort to estimate occupancy rates for the Ivory-billed Woodpecker. In addition I used this case study to highlight several important problems and shortfalls common to many studies involving rare species. These shortfalls motivated the development of several new approaches that provide advances in rare species modeling. First, I developed a framework for allocating effort that provides a probabilistic approach to sampling, allowing for improved accuracy in estimating occupancy probability. This approach was found to have a much lower predictive error rate compared to traditional approaches such as single-season occupancy estimation especially when there was a large amount of spatial heterogeneity in habitat and detection probability was low. Second, I developed a hierarchical model that integrates adaptive cluster sampling and occupancy estimation, which allowed for additional effort to be placed at adjacent sites after a known detection. I found this model to outperform traditional occupancy modeling and provide excellent coverage under a variety of conditions. Future improvements in conservation and management of rare species will be accomplished through a variety of techniques and approaches. Ultimately, I believe the most operative approach will be the integration of unique and innovative methods of data collection coupled with models that identify and subsequently estimate the most important vital rates responsible for driving population dynamics.