Day-roosts of female long-eared Myotis in western Oregon

Roosts are a critical habitat component for bats and may influence their su rvival and fitness. We used radiotelemetry to investigate characteristics o f day-roosts of female long-eared myotis (Myotis evotis) in watersheds char acterized by different forest conditions and the spatial relationships betw een day-roosts and available water. We tracked 21 bats to 73 roosts (n = 10 2 occasions) from June to August 1996 and 1997 on the western slope of the Cascade Mountains, Oregon. Bats primarily used conifer stumps as day-roosts in watersheds dominated by younger forests and used conifer snags, and to a lesser extent conifer stumps, in watersheds with greater proportions of o lder forests. Individual long-eared myotis used different types of structur es as day-roosts, and type of structure used did not differ with reproducti ve condition. Day-roosts were primarily located in upslope habitat and aver aged 0.59 +/- 0.03 km from available water and 0.66 +/- 0.02 km from captur e sites. Roosts were not located closer to available water than random poin ts, but were closer than random points to captures sites. Conifer snags use d as day-roosts averaged 34 +/- 5 m in height and 93 +/- 12 cm diameter at breast height (dbh); snags in intermediate stages of decay had highest use. Use of conifer snags was positively associated with the number of snags wi thin 20 m and negatively associated with distance from stand edge. Conifer stumps used as day-roosts averaged 133 +/- 9 cm in height and 59 +/- 4 cm d bh. Western hemlock and Douglas-fir stumps were used more often than wester n redcedar stumps as day-roosts. Odds of a stump being used as a day-roost increased with increasing height of the stump (downhill side). and whether it was situated in a gap in vegetation. We contend that management of day-r oosts for forest-dwelling bats should focus on maintaining large conifer sn ags across landscapes through space and time. In landscapes where there are relatively few large conifer snags, stumps appear to provide important, bu t ephemeral, roosts for long-eared myotis.