Nocturnal and diurnal habitat of Indiana and northern long-eared bats, and the simulated effect of timber harvest on habitat suitability

Benjamin P Pauli, Purdue University

Abstract

The emergence of White Nose Syndrome (WNS) in the eastern United States threatens many bat species. WNS has caused the deaths of millions of bats and has endangered bat species including those previously considered to be common. Two affected species are the Indiana bat (Myotis sodalis ) and the northern long-eared bat (M. septentrionalis). The Indiana bat is an endangered species that for decades has been the subject of conservation efforts. In contrast the northern long-eared bat previously was considered to have robust populations, but mortalities associated with WNS have resulted in a petition to list this species under the Endangered Species Act. In an effort to mitigate the devastating effects of WNS on bat populations, a multifaceted approach to species conservation is warranted. One aspect of such an effort must be the preservation and promotion of suitable habitat for both species. Because Indiana and northern long-eared bats are found in forested habitats during the summer, forest management offers potential for encouraging suitable habitat. Bats have distinct habitat needs at night for foraging/commuting and during the day for roosting. Thus, identifying the habitat required for each life history need independently is crucial. To assess nocturnal habitat for both species, I used acoustic monitoring at 88 sites across Indiana State Forests. I identified species presence at a site based on the classification of echolocation calls. I used single-species and multi-species occupancy models to determine the environmental variables that best predicted nocturnal occupancy. I found that nocturnal occupancy of both species was dependent upon forest composition. In general, occupancy was maximized in recently harvested or mature second-growth stands with a surrounding landscape composed of a higher proportion of open habitat. In addition, the spatial configuration of water and anthropogenic habitat, particularly roads, affected species occupancy. To identify important diurnal habitat used by bats for roosting I used the locations of known roosting sites for both species in a presence-only modeling framework. This allowed me to identify the features of the broader landscape that most influenced diurnal habitat for both species. The proportion of forest and forest edge were important predictors of roosting habitat though both species exhibited somewhat opposing preferences. Finally, I used forest successional modeling to predict future forest conditions under 9 timber harvest scenarios in Indiana State Forests. I applied both nocturnal and diurnal predictive models for Indiana and northern long-eared bats to simulated forest conditions. In addition, I combined roosting and foraging models for both species in order to assess overall habitat suitability under harvest conditions. I found that suitable habitat for both species was substantially impacted by harvest regime. In general, even-aged regenerative timber harvests created more suitable nocturnal habitat than did selective harvests for both species. Single-tree selection harvests, on the other hand, favored suitable diurnal habitat over the larger openings created by regeneration harvests. The degree of impact was somewhat species specific as Indiana bats were more affected by variation in the intensity and form of timber harvests relative to northern long-eared bats. Taken together my research provides important knowledge and guidance for the conservation of threatened bat species. I identified predictors of quality nocturnal and diurnal habitat for Indiana and northern long-eared bats. Because my environmental predictors were based upon data collected remotely, predictive models of nocturnal and diurnal habitat use can be projected across comparable, large areas to identify important habitat conservation sites. In addition, my simulation models highlight the impacts of varying timber harvest pressure and prescriptions on habitat for bats. I recommend silvicultural approaches that couple regenerative and selection harvests so that they may balance the needs of forest management, timber harvest and conservation of bat habitat.

Degree

Ph.D.

Advisors

Zollner, Purdue University.

Subject Area

Wildlife Conservation|Ecology

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