Seasonal Use and Selection of Caves by the Eastern Pipistrelle Bat (Pipistrellus subflavus)

—The eastern pipistrelle (Pipistrellus subflavus) is considered one of the most common and widely distributed species of bats in eastern North America, but little published information exists on its natural history. During surveys of numerous small caves in northwest Arkansas, we documented use by eastern pipistrelles and recorded ambient temperature readings in all caves and at roost and hibernation sites for individual bats. Using presence/ absence data and a GIS system, we examined association of pipistrelle occurrence based upon landscape-level variables and cave structure. Hibernating eastern pipistrelles showed a significant preference for cave openings with east-facing aspects and significantly avoided caves on steep slopes during winter. These patterns appear to be due to the influence of cave ambient temperature. Significantly more eastern pipistrelles were found in caves with a wide range of temperature regimes within a season, but with little temperature variation between seasons. In our study site caves with east-facing aspects and on shallow slopes were significantly larger than those on the steep west-facing slopes. Larger caves have a greater buffer capacity from weather conditions, offering a wider range of temperature profiles within a season but varying little between seasons for consistent use by hibernating eastern pipistrelle bats.