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    Projecting the compound effects of climate change and white-nose syndrome on North American bat species
    (Elsevier Inc, 2022-12) McClure ML; Hranac CR; Haase CG; McGinnis S; Dickson BG; Hayman DTS; McGuire LP; Lausen CL; Plowright RK; Fuller N; Olson SH
    Climate change and disease are threats to biodiversity that may compound and interact with one another in ways that are difficult to predict. White-nose syndrome (WNS), caused by a cold-loving fungus (Pseudogymnoascus destructans), has had devastating impacts on North American hibernating bats, and impact severity has been linked to hibernaculum microclimate conditions. As WNS spreads across the continent and climate conditions change, anticipating these stressors’ combined impacts may improve conservation outcomes for bats. We build on the recent development of winter species distribution models for five North American bat species, which used a hybrid correlative-mechanistic approach to integrate spatially explicit winter survivorship estimates from a bioenergetic model of hibernation physiology. We apply this bioenergetic model given the presence of P. destructans, including parameters capturing its climate-dependent growth as well as its climate-dependent effects on host physiology, under both current climate conditions and scenarios of future climate change. We then update species distribution models with the resulting survivorship estimates to predict changes in winter hibernacula suitability under future conditions. Exposure to P. destructans is generally projected to decrease bats’ winter occurrence probability, but in many areas, changes in climate are projected to lessen the detrimental impacts of WNS. This rescue effect is not predicted for all species or geographies and may arrive too late to benefit many hibernacula. However, our findings offer hope that proactive conservation strategies to minimize other sources of mortality could allow bat populations exposed to P. destructans to persist long enough for conditions to improve.
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    Ecology of infectious diseases in wild bats : a dissertation presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Veterinary Sciences at Massey University, New Zealand
    (Massey University, 2019) Hranac, Carter Reed
    Emerging infectious diseases present significant threats to the health of humans and wildlife. The ecology of emerging infectious diseases is a data hungry field in a world of rare events. Bats are both the source of human pathogens globally and the victims of a novel fungal pathogen causing continent-wide population declines in North America. By using the principals of iterative model design and model guided field work I leverage the mechanistic relationships between seasonally limiting biotic and abiotic factors of wild bats to understand spatio-temporal disease emergence dynamics from and within bat populations. I first use a novel ecological niche modeling technique to relate the seasonal availability of resources to predict African bat birthing events. I then use these model results to test hypotheses that Ebola virus disease (EVD) transmission to humans and non-reservoir animal hosts are related to the birthing events of bats through the use of a spatiotemporal Poisson point process model. The results suggest EVD emergence in Africa may be driven in part by the pattern of births among bats, especially fruit bats. Further, the identified temporal lag terms between bat birthing terms and EVD emergence are consistent with hypothesized viral dynamics in bat populations. Out of sample testing on the two most recent EVD outbreaks in the Democratic Republic of the Congo reveal a high predictive model performance and suggest the existence of both strong regional seasonality and locations persistently at risk of EVD outbreaks in humans and susceptible wildlife. Finally, I model North American winter duration and incorporate spatial variation in host traits related to body mass and composition to update survival estimates for hibernating Myotis lucifugus infected with Pseudogymnoascus destructans, the causative agent of the emerging disease white- nose syndrome (WNS) killing bats in Eastern North American populations. Results indicate that hibernating M. lucifugus in the West are likely to suffer populations declines similar to those observed in the East. All my findings will require further ground-truthing to validate the results, yet demonstrate the predictive power of identified mechanistic relationships on complex infectious disease systems.