Characteristics of fringed myotis day roosts in northern California

Understanding habitat relationships of forest-dwelling bats has become a wildlife management priority during the past decade. We used radiotelemetry to examine the use of day roosts by fringed myotis (Myotis thysanodes) in a Douglas-fir (Pseudotsuga menziesii) forest in northern California, We located 52 roosts in 23 trees and compared the characteristics of roost sites and structures to random sites and structures. All roost trees were snags in early to medium stages of decay. Bats switched roosts often, and the number of bats exiting roosts varied from 1-88. The most important factor that discriminated roost sites from random sites was 5.4 more snags ≥30 cm dbh at roost sites. Roost sites also had 11% less canopy cover and were 41 m closer to stream channels than random sites. Roost snags were 27 m taller and had diameters 42 cm larger than random snags in the watershed and were 21 m taller and had diameters 30 cm larger than snags nearby the roost. Our results are comparable to findings for other forest-dwelling bat species which conclude that management of day roost habitat requires large numbers of tall snags in early to medium stages of decay.

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