Fall phenology, movement, and roost use of little brown bats and California myotis at Mount Rainier

Little is known about the fall and winter ecology of hibernating bats in western North America. Filling knowledge gaps for these populations has become more urgent with the westward spread of the white-nose syndrome, a disease that infects bats during hibernation. We used radiotelemetry to track little brown bats (Myotis lucifugus) and California myotis (Myotis californicus) from late-August to mid-December in 2021 and 2022 at Mount Rainier National Park to gather information on fall and winter phenology, movement, and roost use. Telemetry signals were lost in mid-to-late fall for all M. lucifugus, likely because they transitioned from fall roosts to subterranean hibernation sites that attenuated telemetry signals. M. lucifugus captured at an all-male roost left their fall roosting area an average of 29 days later than individuals captured at a maternity colony, suggesting site-level differences in hibernation phenology. All M. californicus remained in the study area, suggesting they over-winter locally. We observed a two-tiered pattern in the duration of roost use for M. californicus in late fall, with short-term roost use (2-6 days) punctuating bouts of long-term roost use (12-20 days). M. californicus were still moving between roosts through the end of telemetry effort in mid-December.

Michael Hansen
Oregon State University
US Geological Survey

Presentation given at North Coast & Cascades Science Days, 2024
go.nps.gov/sciencedays
[MORA] [OLYM]