164 
PROCEEDINGS OF THE CALIFORNIA ACADEMY OF SCIENCES 
Series 4, Volume 65, Supplement I 
1970; Kunz, 1973, 1974), and nursing females may be found nearest entrances in warmest parts of 
warmer caves and tunnels, particularly those least likely to be disturbed by people (Tinkle and Pat¬ 
terson, 1965; Hoffmeister, 1986). Later in summer males in Kansas were found to roost in cooler 
caves than females and young, most typically alone or in small groups (Kunz, 1973). Caves used 
by this species in Kansas during warm months were characterized by low fluctuations in tempera¬ 
tures and relative humidity (which remained at about 100%) whereas roosts in buildings had much 
greater variation in these climatic factors (Kunz, 1973). Foraging females leave young behind at 
the roosts during the early night but they soon return to nurse them (Kunz, 1973). Roosting cave 
myotis in Kansas form clusters that can increase surrounding temperatures by four to 12°C, and 
also can significantly increase humidity (Kunz, 1973). 
Summer colonies may typically number 2,000-5,000 bats, with a maximum of 15,000 to 
50,000 estimated in past surveys (Twente, 1955b; Dunnigan and Fitch, 1967; Hayward, 1970). 
Although this species is vulnerable to disturbance, the majority of one large (30,000 to 50,000 bats) 
colony in Kansas occupied a lighted area of an active gypsum mine in the immediate area of a fre¬ 
quently used ore-train track (Dunnigan and Fitch, 1967). 
Banded individuals from summer colonies in mines in mountain ranges in southern Arizona 
showed year-to-year switches among specific min es but had fidelity to a larger area encompassing 
groups of mines (Hayward, 1970), similar to above findings in the western Great Plains. Within- 
season shifts in population sizes at specific caves during the maternity period were also noted over 
a larger geographic area encompassing multiple caves in northwestern Oklahoma, with movements 
among caves documented through band recoveries (Humphrey and Oli, 2015). Maximum emer¬ 
gence counts at three of these maternity caves were 7,420 bats, 7,179 bats, and 4,620 bats with a 
maximum of 14,583 bats counted over the full core area; post-lactation peaks in counts were not 
obvious, suggesting rapid dispersal of weaned young (Humphrey and Oli, 2015). 
In Mohave County, Arizona, abandoned mine tunnels used as transient roosts by small num¬ 
bers of individuals also housed a maternity colony of about 1,000 in mid-summer, but dropped to 
a single bat by early August (Cockrum et al., 1996). In nearby San Bernardino County, California, 
an abandoned mine had a seasonal peak count of about 5,000 bats during 2013 (Brown, 2013). 
Examples of other maternity colony sizes recently reported include 10,000-12,000 bats each in two 
caves and 8,000 to 10,000 bats each in two bams in the Red Hills of southern Kansas during 2004 
(Marquardt and Choate, 2009), and 700-800 in an abandoned mine on the Arizona side of the 
Havasu National Wildlife Refuge (Brown, 2013). (See also “Population Trend” below.) 
Cave myotis may appear at nursery colony sites in caves on the Edwards Plateau in Texas in 
early February during warm years (Raun and Baker, 1958). In Baja California, Mexico, a colony 
of about 5,000 females and young was reported from a cave, a male colony of about 25 bats were 
reported from a mine tunnel, and about 100 females and young occupied a doorsill of an abandoned 
adobe house (Jones et al., 1965). 
Cave myotis are well-known to share roosts with Brazilian free-tailed bats and Yuma myotis 
in summer (Stager, 1939; Cockmm et al., 1996; Brown, 2013). Roosts are often located near water, 
and they have been observed moving directly to water to drink after emergence (for example, Bai¬ 
ley, 1931; Twente, 1955b). 
Cave myotis will roost in nests of swallows. Individuals have been observed roosting solitar¬ 
ily in 18 of 57 barn swallow {Hirundo rustica ) nests in Texas during late August (Jackson et al., 
1982) and roosting in twos and threes in abandoned cliff swallow (Petrochelidon pyrrhonota ) nests 
in western Texas during late September (Ritzi, 1999). They were found in both cliff and bam swal¬ 
low nests in six counties in south-central Texas in all months of the year except January, with a 
maximum of 14 found in two nests (Pitts and Schaminghausen, 1986). Nine individuals were found 
