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Roosting habits of four bat species in the Black Hills of South Dakota

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Cryan P. M. , Bogdan M. A. , Yanega G. M.

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tom 03

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nr 1

EN

The availability of suitable roosts influences the distribution and abundance of bats. Quantifying roosting requirements is a necessary step toward effectively monitoring, managing, and conserving bats. Our objectives were to locate and characterize the natural, daytime summer roosts of Myotis septentrionalis, M. thysanodes, M. volans, and Eptesicus fuscus in the Black Hills of South Dakota, USA and compare local roosts to those used in other regions. Bats were marked with radio transmitters and followed to roosts. We successfully tracked 37 bats of four species to a total of 81 roosts. Myotis septentrionalis and E. fuscus consistently used trees, while M. thysanodes and M. volans used both trees and rock crevices. Roost trees were consistently among the largest available and were found in areas of relatively high snag densities. Maintaining forests with high snag densities and large trees will likely benefit bat populations in the Black Hills. All species switched roosts, but generally remained within small (=4 km2) areas. Lactating M. thysanodes changed roosts together while carrying young. Fidelity to roosts and roost areas was demonstrated by bats in the Black Hills.

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Not to put Too fine a point on it - does increasing precision of geographic referencing improve species distribution models for a wide-ranging migratory bat?

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Hayes M. A. , Ozenberger K. , Cryan P. M. , Wunder M. B.

Acta Chiropterologica

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2015

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tom 17

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nr 1

EN

Bat specimens held in natural history museum collections can provide insights into the distribution of species. However, there are several important sources of spatial error associated with natural history specimens that may influence the analysis and mapping of bat species distributions. We analyzed the importance of geographic referencing and error correction in species distribution modeling (SDM) using occurrence records of hoary bats (Lasiurus cinereus). This species is known to migrate long distances and is a species of increasing concern due to fatalities documented at wind energy facilities in North America. We used 3,215 museum occurrence records collected from 1950–2000 for hoary bats in North America. We compared SDM performance using five approaches: generalized linear models, multivariate adaptive regression splines, boosted regression trees, random forest, and maximum entropy models. We evaluated results using three SDM performance metrics (AUC, sensitivity, and specificity) and two data sets: one comprised of the original occurrence data, and a second data set consisting of these same records after the locations were adjusted to correct for identifiable spatial errors. The increase in precision improved the mean estimated spatial error associated with hoary bat records from 5.11 km to 1.58 km, and this reduction in error resulted in a slight increase in all three SDM performance metrics. These results provide insights into the importance of geographic referencing and the value of correcting spatial errors in modeling the distribution of a wide-ranging bat species. We conclude that the considerable time and effort invested in carefully increasing the precision of the occurrence locations in this data set was not worth the marginal gains in improved SDM performance, and it seems likely that gains would be similar for other bat species that range across large areas of the continent, migrate, and are habitat generalists.

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Ultraviolet vision may be widespread in bats

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Gorresen P. M. , Cryan P. M. , Dalton D. C. , Wolf S. , Bonaccorso F. J.

Acta Chiropterologica

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2015

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tom 17

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nr 1

EN

Insectivorous bats are well known for their abilities to find and pursue flying insect prey at close range using echolocation, but they also rely heavily on vision. For example, at night bats use vision to orient across landscapes, avoid large obstacles, and locate roosts. Although lacking sharp visual acuity, the eyes of bats evolved to function at very low levels of illumination. Recent evidence based on genetics, immunohistochemistry, and laboratory behavioral trials indicated that many bats can see ultraviolet light (UV), at least at illumination levels similar to or brighter than those before twilight. Despite this growing evidence for potentially widespread UV vision in bats, the prevalence of UV vision among bats remains unknown and has not been studied outside of the laboratory. We used a Y-maze to test whether wild-caught bats could see reflected UV light and whether such UV vision functions at the dim lighting conditions typically experienced by night-flying bats. Seven insectivorous species of bats, representing five genera and three families, showed a statistically significant ‘escape-toward-the-light’ behavior when placed in the Y-maze. Our results provide compelling evidence of widespread dim-light UV vision in bats.