O’SHEA, CRYAN & BOGAN: UNITED STATES BAT SPECIES OF CONCERN 
163 
Cave System in northwestern Oklahoma has consistently contained tens of thousands of cave 
myotis during winter in recent decades (Loucks and Caire, 2007; Creecy et al., 2015). 
In southern Kansas and northwestern Oklahoma, cave myotis studied during 1952-1953 
moved from caverns used in autumn to other caves used as winter hibemacula, where the largest 
colony size was about 7,000 bats in a single cave (Twente, 1955a,b). Bats in the latter cave were 
found in large clusters of about 200, smaller clusters, or as pairs or solitary individuals; some 
movements of banded bats among hibemacula were noted within the winter season (Twente, 
1955a). Areas of caves with cold temperatures and low air circulation were favored, and sizes of 
clusters increased as the winter progressed (dense clusters of 1,700 bats per square meter were 
reported); bats dispersed to warmer caves in late March and early April (Twente, 1955b). Winter 
roosting can occur over water or in damp conditions above cave floors (Hibbard, 1934). Addition¬ 
al studies of use of these and other caves and mines by this species in southern Kansas took place 
during 1963-1966, and provided additional information on numbers of hibernating bats, sex ratios, 
and movements, which were mostly local (Dunnigan and Fitch, 1967). Twenty winter roosts in 
northwestern Oklahoma were studied further during 1966 to 1977, with an emphasis on movements 
and demography as determined through banding (Humphrey and Oli, 2015). Little movement away 
from the study area occurred, with 90% of 200 bats marked as juveniles and 81% of 559 adults 
marked in summer recaptured in the core area caves during winter (Humphrey and Oli, 2015). 
Banded individuals will switch hibemacula between winters (Humphrey and Oli, 2015). 
Populations of cave myotis in Kansas, Oklahoma, and northwestern Texas inhabit the same 
region year-round (Tinkle and Patterson, 1965; Kunz, 1974; Humphrey and Oli 2015). A single 
individual was netted over water in the Trans-Pecos region of Texas in late February (Yancey, 
1997). In California and Arizona, large overwintering populations are poorly known, and some 
may move southward into Mexico where hibernation may occur at higher elevations (Fitch et al., 
1981). However, Cockrum et al. (1996) speculated that cave myotis from lower elevations in 
Mohave County, Arizona may move upslope to hibemacula at higher elevations. In southern Ari¬ 
zona, they are thought to move southward with just a few individuals (fewer than 15 bats, rather 
than colonies) remaining to hibernate in abandoned mines at elevations higher than about 1,825 m, 
where conditions are wet and air circulation patterns result in temperatures of about eight to 11°C 
(Hayward, 1970). Despite records of warm-season colonies in abandoned mines along the Lower 
Colorado River of southeastern California and western Arizona, only small numbers of overwin¬ 
tering cave myotis have been found in these mines (Brown, 2013). Similarly, only small numbers 
were found utilizing bridges as roosts during winter in southern Arizona (Wolf and Shaw, 2002). 
Warm Season Roosts: Colonies of cave myotis can be found in caves and mines, in buildings 
(for example, Kunz 1973), and under bridges (for example, Hoffmeister, 1986; Wolf and Shaw, 
2002). In Kansas, small, widely scattered transient colonies occur in early spring prior to materni¬ 
ty colony formation, and in autumn prior to the hibernation period (Kunz, 1974). Smaller cluster 
sizes also have been observed in Arizona during spring and autumn (when torpor is more evident) 
in comparison with summer, and during spring and autumn they will roost in a wider variety of sit¬ 
uations, including buildings, carports, and swallow nests (Hayward, 1970; see also above). 
Vaughan (1959) described summer daytime roosts in deserted mine tunnels in the Riverside 
Mountains of southeastern California, where this species was absent in winter and early spring. 
They were found in clusters of several to over one hundred in crevices, drill holes, and irregular or 
hollowed-out areas on the ceilings. Tunnels each contained from several hundred to roughly 1,000 
individuals, and these bats were usually most abundant in clusters at the deeper parts of tunnels 
more than about 20 meters from the entrances. 
Maternity colonies may include both males and females, at least up until parturition (Hayward, 
