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PROCEEDINGS OF THE CALIFORNIA ACADEMY OF SCIENCES 
Series 4, Volume 65, Supplement I 
als. Roosts were located in horizontal fissures in large flat boulders or in small crevices or cavities 
(openings averaging 2.3 by 3.7 centimeters, depths averaging 16.7 centimeters) in sedimentary 
rock on eroded hillsides or vertical banks. Most roosts faced westerly or southerly directions. Ten 
roosts had either a single bat, or a bat with an offspring, one roost held four lactating females and 
five non-volant juveniles, and another roost had two adult females and one offspring; one adult 
male was found roosting solitarily about 0.4 kilometers from the area where females were found 
(Tuttle and Heaney, 1974). 
Roosts of western small-footed myotis were discovered through radio tracking bats captured 
in the South Saskatchewan River valley, near Bindloss, Alberta, a badlands area with short-grass 
prairie dissected by coulees and exposed sandstone and mudstone cliffs and hoodoos (Lausen, 
2007). Eighteen females (15 lactating or pregnant) were tracked to 30 roosts. Roosts were found 
either in mudstone or harder, boulder-like substrates. More roosts were in small cavities (erosion 
holes) or crevices in mudstone than were in solid boulders, and roosts were usually occupied by 
only one or two bats (mean group size of 1.4 ± 0.2, range one to five; Lausen, 2007). Roost switch¬ 
ing was frequent, with individuals rarely using the same roost on consecutive days but moving a 
mean distance of 45 meters between roosts (range 6.4 to 106 meters). The first roost discovered for 
each of the tracked bats ranged from four to 580 meters from the point of capture (mean 146 ± 23 
meters). Openings to roosts used by pregnant females were 20.2 ± 6.5 square centimeters and did 
not differ from openings to roosts used by lactating bats (38.4 ± 19.6 square centimeters), but both 
were significantly smaller than those of randomly selected crevices (301 ± 58 square centimeters); 
roost entrances faced south more often than randomly available crevices but were not different in 
distance from flat ground above and below, depth, slope, and crevice orientation (Lausen, 2007). 
Roosts chosen during lactation warmed more quickly after sunrise than roosts used during preg¬ 
nancy. 
In central Oregon, nine female western small-footed myotis were radio tracked during summer 
at John Day Fossil Beds National Monument (Rodhouse and Hyde, 2014). They roosted in small 
crevices (oriented both vertically and horizontally) in rock outcrops in small canyons and to a less¬ 
er degree in larger cliffs; roosts averaged 4.5 meters above ground but roosts of lactating females 
were situated higher than those of post-lactating females (Rodhouse and Hyde, 2014). Roosts were 
located 0.3 to 10.5 kilometers from the over-water capture sites. They primarily roosted solitarily, 
but group sizes of two to 15 bats were observed; lactating females roosted in groups but post-lac¬ 
tating females roosted alone. During the nine- to 12-day tracking periods roost switching occurred 
almost daily with a total of 43 roost locations discovered; just eight roosts were used twice on con¬ 
secutive days, one roost was used for four consecutive days, and all others were used just once 
(Rodhouse and Hyde, 2014). Most females showed fidelity to a broad roosting area, with roosts 
ranging 30 to 347 meters apart within these areas. Similar to findings in Oregon, Cryan (1997) 
found two females roosting together during summer in a narrow (two centimeters) crevice 10 cen¬ 
timeters deep in a broken rock at the base of a sandstone cliff. Quay (1948) reported a male and a 
female roosting solitarily in small pockets under different sheets of rock in western Nebraska, and 
Neubaum (2017) radio tracked a lactating female to a crevice in a boulder in western Colorado. 
Warm Season Roosts in Buildings, Under Tree Bark, and in Swallow Nests: A maternity 
colony numbering over 37 adult and young western small-footed myotis was reported roosting 
between the interior wall and loose wallpaper in an abandoned house in San Luis Obispo County, 
California (Koford and Koford, 1948). A maternity colony also was observed roosting in the attic 
space of a residence near Fort Collins, Colorado (O’Shea et al., 2011b). In Nebraska, a few have 
been taken from bams (Webb and Jones, 1952), a solitary bat was found roosting between two 
boards leaning on a shed (Stephens, 1945), and two bats were reported roosting under a loose strip 
