"The hemorrhagic diseases (HD) epizootic hemorrhagic disease (EHD) and bluetongue (BTV) are the most significant source of viral-related mortality of deer in the United States. The emergence of HD on the landscape is affecting the population ecology of white-tailed deer (Odocoileus virginianus) in previously unaffected regions of North America. The forces driving apparent increases in HD are poorly understood, particularly where the disease has recently been most severe in northern latitudes. Specifically, Michigan has seen an increase in EHD related deer mortality since 2006, and 2012 was the largest outbreak of EHD in Michigan history. My research seeks to address current uncertainties for deer populations with regard to impacts from emergent HD. In this dissertation I attempt to investigate the local distribution and population-level impacts on deer in areas affected by EHD, develop and apply population estimation techniques appropriate for localized population change assessment, and evaluate landscape-level drivers of HD across an epidemiological gradient. I estimated the annual population abundance of deer immediately after a recent EHD outbreak over a 4-year period and quantified the fine-scale spatial extent of EHD impacts associated with riparian habitats. I assessed these differences in deer abundance for sites affected and unaffected by EHD in Michigan. I determined if populations increased over time in response to local population impacts from EHD. I then validated estimates using an independent aerial survey and a novel application of N-mixture models. I evaluated the N-mixture model against distance sampling methods and tested the sensitivity of N-mixture model estimates to variation in spatial unit size. At a regional scale, I evaluated the role of drought severity in both space and time on changes in HD reports to determine if drought severity explains changing patterns of HD presence. Important findings from my research include 1) abundance estimates in the affected area were significantly lower along transects near the river, reflecting EHD mortality associated with wetlands; 2) the opposite was true in the unaffected site; 3) estimates from both distance sampling and N-mixture modeling approaches were similar and aerial surveys using N-mixture binomial models are a practical tool for estimating abundance of a free-ranging wildlife population; 4) the selected spatial unit size in the N-mixture model had a significant effect on abundance and detection probability estimates, and their associated variance; 5) drought severity was a significant predictor of HD presence and the significance of this relationship was dependent on latitude; 6) the effect of drought was reduced or non-existent in most southern states, where the disease is endemic. My findings suggest that EHD outbreaks will have population impacts near riparian corridors and those populations can increase post-outbreak. Further, N-mixture models may provide an improved approach to estimate populations from aerial surveys in the future, although managers and researchers should evaluate the spatial unit used for these models prior to survey implementation. While drought severity does increase the probability that HD will be detected and reported at a county level, my research points to the underlying role of acquired herd immunity across the endemic-to-emergent disease gradient."--Pages ii-iii.
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