Structural and environmental predictors of tricolored bat presence and abundance in Texas caves

Authors: Melissa B. Meierhofer, Samantha J. Leivers, Brian L. Pierce, Garrett W. Powers, Jonah W. Evans, Michael L. Morrison

The identification of bat colonies is essential to conserve and manage these globally threatened mammals. Caves
offer potential roosting locations (hibernacula) to hibernating bat species; however, identifying regions where bat-occupied caves exist can be time-consuming. In Texas, caves are often on privately owned land, creating difficulties for accessing and managing potential hibernacula. The tricolored bat (Perimyotis subflavus), a species susceptible to white-nose syndrome, hibernates in caves in the winter in Texas. We sought to identify and quantify site-specific structural and environmental features that influence the presence and abundance of overwintering tricolored bats. We surveyed caves for bats and recorded environmental and structural features of 116 caves January–February 2016, December–February 2016–2017, January–February 2018, and December–February 2018–2019. We used a zero-inflated Poisson regression to identify which features best explained the presence and abundance of tricolored bats. We found that bat presence increased as cave length decreased, and as Normalized Difference Vegetation Index (NDVI) and external vapor pressure deficit increased. Bat abundance increased as number of portals, cave length, NDVI, and external temperature increased. Combining surface data with subsurface features can assist with identifying specific karst regions and known caves within those regions for survey and management efforts.

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