Correlates of cave-roosting bat diversity as an effective tool to identify priority caves

Cave ecosystems are subterranean biodiversity hotspots, but limited knowledge of the distribution of diversity among caves hampers their conservation. Surveys of surrogate taxa (e.g., keystone species) can identify hotspots of biodiversity when knowledge about an ecosystem is lacking. Bats are keystone species in cave ecosystems because their guano is the primary energy source supporting diverse assemblages of cave-dependent wildlife. However, directly measuring bat diversity is time-consuming and requires expert knowledge; instead, we suggest the use of correlates of bat diversity that can be derived from readily accessible data (e.g., land-use maps) and straightforward methods not requiring expert knowledge (e.g., cave surveys, interviews) as a foundation for prioritizing caves. To identify easily measurable correlates of bat diversity, we compared assemblage composition and species abundances of 21 bat species captured in 56 caves on Bohol Island, Philippines, along gradients in environmental factors and human disturbance. Model- and distance-based methods indicated that surface-level disturbance (i.e., percent non-forested habitat, degree of urbanization and road development) along with cave complexity (i.e., available roosting area, structural heterogeneity, number of entrances and temperature range) were the most influential factors governing cave-roosting bat assemblages, thus representing correlates of bat diversity. Prioritization schemes based on these correlates select combinations of caves with greater species richness than both random selection and selection of caves based on observed richness from intensive bat surveys. The use of easy-to-measure environmental and disturbance correlates of bat diversity is an effective tool to prioritize caves to protect cave-roosting bats and the cave-dependent wildlife they support.