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PROCEEDINGS OF THE CALIFORNIA ACADEMY OF SCIENCES 
Series 4, Volume 65, Supplement I 
were in rock crevices on steep slopes or in cliff faces of canyon walls at a mean elevation of 2,180 
meters, with a group of 131 bats observed exiting at emergence at one roost (logistic and safety 
issues prevented counts at other roosts; O’Shea et al., 2011a). In western Colorado, Neubaum 
(2017) radio tracked six reproductive females to seven roosts, five in crevices in cliffs and two in 
trees. 
Warm Season Roosts in Trees and Snags: Roosting habits of long-legged myotis have been 
studied in detail in forests of the Pacific Northwest. In Douglas fir forests of the western Oregon 
Cascade Mountains, Amett and Hayes (2009) located 105 roosts of 55 radio-tracked females in 
conifer snags. Bats primarily used Douglas fir (but at a frequency that did not differ from that of 
randomly available snags), with western hemlock and western red cedar snags used at a much 
lower frequency. Snags used as roosts were in stands that were mostly greater than 40 years old 
(Amett and Hayes, 2009). Individuals used one to eight unique roosts (mean 2.8 ± 0.2 SE roosts) 
during one to 18 days of radio tracking (mean 8.4 ± 0.6 SE days), switching roosts up to eight times 
(mean 2.5 ± 0.3 SE switches) during tracking periods. Use of snags was higher as tree girth 
increased, and as the number of smaller snags nearby increased (Amett and Hayes, 2009). The 
roosting habits of this species also were studied in the central Oregon Cascades (Ormsbee, 1996; 
Ormsbee and McComb, 1998). Radio-tagged bats were tracked to 41 roosts: 36 in snags, four in 
live trees, and one in a rock crevice. Snags used as roosts ranged from 33 to 44 meters in height 
(95% Cl) and 83-110 centimeters in diameter (95% Cl), with 72% in Douglas fir snags and the 
remainder in western hemlock or western red cedar snags (Ormsbee and McComb, 1998). Snags 
used as roosts were generally higher than the surrounding canopy and were more often found in 
uplands rather than riparian habitats, although roost snags were closer to streams than randomly 
selected locations (Ormsbee and McComb, 1998). Bats followed in this study switched roosts 
about every two days but tended to roost in groups of trees within a discrete area (Ormsbee, 1996). 
The largest maternity group observed was over 300 bats in a fire-hollowed western red cedar; fire 
hollows are rare and have different microclimates than cracks in snags (Ormsbee, 1996; Ormsbee 
and McComb, 1998). 
In ponderosa pine-dominated forests of the eastern Cascades of Oregon and Washington, 
Baker and Lacki (2006) radio tracked 87 adult females and located 229 roosts (195 snags and 34 
in rock crevices). Bats were tracked for an average of 9.7 ± 1.1 SE days (range 1-24) and used up 
to 10 unique roosts, averaging 3.6 ± 0.3 SE roosts during each tracking period, and switching roosts 
every 2.7 ± 0.2 days (range one to 20; Baker and Lacki, 2006). Distances between successive roosts 
averaged 1.4 ± 0.1 SE kilometers. About half of the roosts in snags were in ponderosa pine, with 
most of the remaining snags in grand fir (Abies grandis ) and white fir (A. concolor ). Nearly all 
roosts in snags were under exfoliating bark. Thermal regimes under exfoliating bark at roosts used 
by long-legged myotis in these two species of trees as measured in Oregon and Idaho were warmer 
than ambient at night; temperatures under bark are more stable than ambient air, favoring torpor in 
the coolness of morning with passive re-warming later in the afternoon (Lacki et al., 2013). About 
half of the roosts were of solitary individuals, a third housed two to 49 bats, and the remainder from 
50 to 459 bats (Baker and Lacki, 2006). Group sizes were smaller prior to parturition. Lactating 
and postlactating females favored snag roosts that were located more upslope and had thicker exfo¬ 
liating bark, perhaps because thicker bark may confer greater thermal stability for developing 
young (Baker and Lacki, 2006). Larger colonies used snags that were larger in diameter (a gener¬ 
al preference for larger snags was also found by Johnson et al., 2007 in Idaho) and taller than snags 
used by small groups and individuals; all snags used as roosts were larger, taller, and had more 
remaining bark than randomly sampled snags. Snag roosts were found in areas with high densities 
of other large snags (Baker and Lacki, 2006). Attrition of snags used as roosts was 22.7% over a 
single year in the eastern Cascades study (Baker and Lacki, 2006). 
