O’SHEA, CRYAN & BOGAN: UNITED STATES BAT SPECIES OF CONCERN 
47 
unoccupied caves, caves used as hibemacula were farther from ephemeral water sources. Factors 
that may have been important but lacked statistical significance (a = 0.05) in univariate analysis 
included observations suggesting that occupied caves seemed longer, had higher ceilings, more 
constrictions, and higher levels of humidity. A multivariate discriminant analysis indicated that 
three factors were of importance for occupancy: increased distance from ephemeral water, cave 
height, and presence of collapses or constrictions. The likely biological reasons for these findings 
were not entirely clear (Gillies et al., 2014). 
Townsend’s big-eared bats may arouse and change positions within or among hibemacula dur¬ 
ing winter (Twente, 1955a; Kunz and Martin, 1982; Genter, 1986), and winter-feeding activity may 
occur (Pearson et al., 1952; Ingersoll et al., 2010). Three individuals captured during winter over 
watering sites in New Mexico, however, did not show signs of active feeding (Geluso, 2007). This 
species tends to select the colder parts of caves and mines for hibernation rather than the warmest 
chambers and may be found close to entrances or in other well-ventilated areas, but they will shift 
to deeper, more thermally stable areas during winter extremes (Kunz and Martin, 1982 and refer¬ 
ences therein). Lowest mean monthly temperatures at Kansas and Oklahoma roost sites ranged 4.6 
to 5.5°C, and these sites had strong to moderate airflow (Humphrey and Kunz, 1976). In Idaho, 
these bats hibernated in lava-tube caves, but not those with extensive subfreezing temperatures, 
with nine of 31 caves surveyed harboring from seven to 132 bats (Genter 1986). In California, 
hibernating temperatures at 33 sites averaged 7.1°C (Pierson and Rainey, 1998a). Interim roosts 
may be used by females subsequent to hibernation but prior to formation of maternity colonies 
(Dobkin et al., 1995). 
Warm Season Roosts in Caves and Mines: Day roosts for 100 bachelor groups and 12 mater¬ 
nity colonies of Townsend’s big-eared bats were found in the mines and caves surveyed in Utah by 
Sherwin et al. (2000). Maternity colonies numbered up to 550 mature females, averaging 129 
females per site (Sherwin et al., 2000). They were more likely to be found in caves or mines with 
single openings, smaller entrances, and little evidence of human disturbance. Maternity groups, 
however, favored caves over mines and tended to use complex sites with multiple openings and 
multiple internal levels with large internal dimensions; unfortunately these sites also showed signs 
of frequent human disturbance (Sherwin et al., 2000). A subsequent study of 1,345 mines and 47 
caves surveyed at multiple times of the year in 6 study regions of Utah and Nevada had objectives 
of determining patterns of roost fidelity and use in relation to habitat characteristics (Sherwin et al., 
2003). Townsend’s big-eared bat use was found at 590 sites, with used caves and mines mainly 
located below 2,600 meters in elevation; other patterns of habitat associations varied by study 
region (Sherwin et al., 2003). Most caves were used year-round, but mine use varied seasonally, 
with evidence of much discontinuous use of mines within seasons due to movement between 
roosts, particularly in small colonies within warm seasons; even maternity colonies moved to an 
average of three roosts in mines (range one to 9) every zero to seven days within a summer but fol¬ 
lowing predictable patterns, whereas high fidelity was shown to caves (Sherwin et al., 2003). This 
study showed that intensive fieldwork and careful analysis is required for regional management of 
abandoned mine habitats for Townsend’s big-eared bats. 
Humphrey and Kunz (1976) recognized four seasonal roosting phases of Townsend’s big- 
eared bats in Kansas and Oklahoma: nursery or maternity groups, summer males, winter popula¬ 
tions, and occasional transient groups. In that region, females form maternity colonies of 17-40 
adults in summer and cluster in warmest reaches of caves, mines, and buildings. (Early authors sug¬ 
gested that adult females do not cluster in maternity roosts [for example, Howell, 1920a], but many 
others have since reported such clusters, which are essential to bioenergetics of reproduction). 
Females in maternity groups in Oklahoma caves occupied warm ceiling domes seven to 12 meters 
