as 1993 was an unusually wet year. For example, 21 passes and 7 

 feeding buzzes were detected in . 5 hours at Sutton Creek on 31 

 July. On 11 September, only 11 passes and 1 feeding buzz were 

 detected on the same transect, in conditions of heavy wind and 

 periodic rain. At other sites, inclement weather occurred during 

 both transect nights (e.g., Ross Creek Cedars), possibly 

 influencing bat activity. Although poor weather often diminishes 

 bat activity, bats were sometimes observed foraging in rain. M. 

 lucifugus, M. evotis, and M. californicus were all captured during 

 moderate rain shortly after sunset on 31 May. All captured bats 

 were adult females, one of which was identifiably gravid {M. 

 lucifugus) . Greater nutritional needs may require gravid females 

 to forage in less than optimal conditions . Above average 

 precipitation in the study area during the summer may have forced 

 bats into foraging during poor weather out of necessity. 



The time of year at which sites are sampled, and the corresponding 

 changes in bat activity due to reproductive progression and 

 migration may potentially affect bat activity, although Thomas and 

 West (1991) generally did not find significant temporal changes in 

 the levels of activity in the southern Washington Cascades and 

 Oregon Coast Range. In this study, 10 passes and feeding buzzes 

 were detected in . 5 hours of monitoring at Rock Creek on 19 May. 

 On 27 September, following parturition, 3 passes and 6 feeding 

 buzzes were detected in 28 minutes under similar environmental 

 conditions. These results could signify the activity of juvenile 

 bats, or the movement of adult bats from maternity roosts along 

 drainages to hibernacula. At other sites, lower levels of bat 

 activity were obtained from sanpling late in the year. Low 

 relative bat abundance was found at both transect locations in the 

 Beaver Creek drainage, and sites on the Superior Ranger District 

 (Dry Fork, Slowey Gulch, and Dry Fork) after mid-September. Rock 

 Creek provides an exception to the low levels of bat activity 

 generally found late in the study. 



Most transects were along roads and creeks, which bats likely use 

 as flyways between roost sites and feeding areas. Roads may also 

 be utilized as foraging habitat in upland forests (Christy and 

 West 1993) . Due to the heterogeneity of habitat types often 

 encountered along transect routes, it is difficult to correlate 

 levels of bat activity obtained during this study with forest 

 characteristics (e.g., age structure or snag density) in the 

 immediate vicinity of the transect. Since bats may be expected to 

 limit the distance they travel to the smallest range possible in 

 order to conserve energy (Christy and West 1993), bats detected 

 during this study likely find roosting habitat within the drainage 

 that they are encountered. Therefore, the index of bat activity 

 may be more reliable as a basis for comparing relative bat 

 abundance between different drainages in the study area. 



14 



