Determinant factors of summer roost selection for cave bats (Myotis velifer) in central Texas

Angelo, Sofia
Jon Atwood, PhD
Department of Environmental Studies
Summer roosting populations of the cave bat (Myotis velifer) have abandoned a number of Texas caves, possibly indicating an overall decline of this species. Microclimate and other factors were compared between caves that have been used by M. velifer during the summer and caves that are not known to have been previously used by this species. Eighteen of the caves used in the study were categorized as velifer caves based on current presence, documentation of past occupation or by the presence of roost stain. Sixteen additional caves were categorized as non-velifer caves,' based on the absences of roost stain and any reports of the species' presence. Factors measured at each site included; cave entrance width and height, cave length, temperature, humidity and ceiling height at roost locations or potential roost locations, proximity of a cave to a permanent water source, and vegetation density surrounding the entrance. Past and present cave use by M. velifer was significantly related to disturbance, relative humidity. Also, the height of a roost was found to be a predictor for the area of that roost.