Species Richness and Seasonality of Bat Occupancy on Northwestern National Wildlife Refuges

Bats are critical to ecosystem integrity but are being threatened by a variety of disease and anthropogenic stressors. Further, information is generally lacking on basic parameters necessary for long-term bat conservation in North America, including the timing of seasonal activity and location of overwintering sites. Between 2011 and 2016, we used passive acoustic recording equipment to collect and analyze 115,855 bat calls from six National Wildlife Refuges across three geographic areas in the northwestern United States; the majority of the data was collected from 2014 to 2015. We documented the presence of 16 species, with species richness varying from 6 to 15 species across sampled Refuges. This includes detection of two species outside of their expected ranges: western red bat Lasiurus blossevillii were found in the Great Basin and western pipistrelle Pipistrellus hysperus were found in the Northern Rockies. Overwintering bats were found across all three geographic areas, although only one species, western pipistrelle, was documented as active year round on more than one Refuge. Six species of bats were also identified as potentially overwintering within their respective areas. For suspected nonoverwintering species, including those considered susceptible to white-nose syndrome, dates of first detections began in early March to early May and last detections between early October and early November. Public lands established for conservation can provide important monitoring and conservation resources for bats.