O’SHEA, CRYAN & BOGAN: UNITED STATES BAT SPECIES OF CONCERN 
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of bark (Swenk, 1908). They have been found roosting in swallow nests in western Kansas (Mer- 
riam, 1886). 
Warm Season Roosts in Caves, Mines, and Night Roosting: Bat captures made at the 
entrance to Jewel Cave in South Dakota using a harp trap were dominated by western small-foot¬ 
ed myotis, with this species accounting for 222 of 587 bats of seven species, nearly all males 
(Choate and Anderson, 1997). In contrast, this species accounted for just nine captures out of 209 
bats of nine species netted in summer over watering places near Jewel Cave (Choate and Ander¬ 
son, 1997). It was unclear if the bats taken at the entrance to Jewel Cave were exiting the cave at 
emergence or entering the cave as a night roost. These bats were observed at eight caves in Col¬ 
orado, averaging two bats per cave, although it also was unclear if observations were of night- 
roosting bats or bats roosting internally during the day (Siemers, 2002). Similarly, small numbers 
of individuals were captured in mist nets at the mouth of Azure Cave at 1,361 meters elevation in 
Montana during June to October (Hendricks et al., 2000). In Colorado, they were among the top 
four species found using abandoned mines, based on a sample of 1,903 bats of 11 species found in 
nine years of surveys at 1,800 sites (counts or other details not specified; Navo et al., 2000). 
Western small-footed myotis use night roosts after feeding, as has been documented at sever¬ 
al mines and caves in the Black Hills of South Dakota (Turner, 1974). They were not observed 
using bridges as night roosts along the upper Sacramento River in northern California (elevations 
320-730 meters), although several other species of bats were well documented using these struc¬ 
tures during the night (Pierson et al., 1996b). In contrast, bridges were used as night roosts of this 
species in the central Sierra Nevada of California (elevations greater than 1,000 m; Pierson et al., 
2001 ). 
Population Ecology. — Litter Size, Natality, and Female Reproduction: Cockrum 
(1955) summarized records for nine female western small-footed myotis from multiple locations, 
each with single embryos. Subsequently at least three females with single young were also report¬ 
ed from South Dakota (Turner and Jones, 1968; Turner, 1974; Famey and Jones, 1980), three 
females with one embryo each were taken in southwestern North Dakota (Genoways and Jones, 
1972), as were two females in Nebraska (J.K. Jones, 1964; Geluso and Geluso, 2016), a single 
female from southeastern Montana (Jones et al., 1973), and a female from northwestern Colorado 
(Finley et al., 1983). However, one case of twinning in addition to three cases of singletons were 
reported in a roost in the Badlands of South Dakota (Tuttle and Heaney, 1974). 
Natality estimates for western small-footed myotis can vary greatly but are sometimes low 
compared to estimates for other species. In prairie badlands of southern Alberta, an overall repro¬ 
ductive rate of 351 adult females captured away from roosts during the lactation period in summers 
2001-2005 was 56% (Lausen, 2007). In southeastern Montana, one of six females taken over water 
was reproductive (Jones et al., 1973). Eleven of 14 females taken at Badlands National Park on 
June 30 and July 3, 1970 were reproductive (Famey and Jones, 1980). The proportions of adult 
females captured at watering places in southwestern Colorado that were reproductive varied with 
the amount of spring precipitation, averaging 30% in 20 females during a drought year and 63% in 
27 females the following year, when spring precipitation and corresponding warm-season insect 
abundance were higher (Snider, 2009; O’Shea et al., 2011a). Twenty-one of 51 adult females (41%) 
captured during summer in west-central Nevada were reproductive (Kuenzi et al., 1999). Fourteen 
of 18 (78%) females captured over water in the Jemez Mountains of New Mexico during 1995 to 
1997 (including a drought year) were reproductive (Bogan et al., 1998). Each of seven females 
(100%) netted over water or taken by shooting in the Mogollon Mountains in New Mexico and Ari¬ 
zona was reproductive during June and July 1960 to 1961 (C. Jones, 1964). 
Cryan (1997) reported 83% of 12 female western small-footed myotis captured over water in 
