Cooperative Fish and Wildlife Research Units Program: Virginia
Education, Research and Technical Assistance for Managing Our Natural Resources

Species composition in ecological communities, or community assemblage, is driven by resource competition and stochastic processes. Emerging infectious diseases present a major perturbation with apparent direct effects such as reduced population density, extirpation and/or extinction. However, little is known about the potential indirect effects of disease that likely alter community assemblages and larger ecosystem function. Considerable evidence exists concerning niche partitioning in sympatric bat species, and the unprecedented, rapid decline in multiple species may provide an opportunity to observe a dramatic restructuring of the community assemblage. Since 2006, white-nose syndrome (WNS) has resulted in the loss of over 6 million hibernating bats in eastern North America. Acoustical monitoring during 2003-2011 allowed us to test the hypothesis that spatial and temporal niche partitioning by bats was relaxed post-WNS. We detected 9 bat species pre- and post-WNS. Activity by almost all species declined post-WNS. Dramatic post-WNS declines in activity of little brown bat (Myotis lucifugus, MYLU), formerly one of the most abundant bat species, were associated with complex, often species-specific responses by other species that generally favored increased spatial and temporal overlap with MYLU. Collectively, in addition to the obvious direct effects of disease on bat populations and activity levels, our results provide evidence that disease can alter community assemblage through the relaxation of both temporal and spatial niche partitioning. Recent occurrence of WNS in North America, combined with multiple existing stressors, is resulting in dramatic shifts in bat community assemblage. These changes may influence long-term bat species population viability and the broader concern of ecosystem structure and function.