Little brown bats were once one of the most common bats in Oregon’s forests, but white-nose syndrome, a fungal disease that spreads through hibernating colonies, has cut populations sharply since reaching the West Coast. The species’ global IUCN status now sits at Endangered, and Oregon’s own S3, vulnerable, rank tells a similar story. Records cluster around the Deschutes and Willamette National Forests, where mountain lakes and meadows give this bat open water to drink and hunt insects over at dusk.
Records build through early summer to a sharp August peak, more than twice any spring month, tracking the maternity season when females and pups are most active on the wing. Winter records drop to almost nothing, consistent with a species that retreats to caves and mines to hibernate rather than staying active through cold months.
Full species profile
