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PROCEEDINGS OF THE CALIFORNIA ACADEMY OF SCIENCES 
Series 4, Volume 65, Supplement I 
from about 50 to 15,000 bats and suggested a summer population of 500,000 cave myotis in the 
region around 1960. T ink le and Patterson (1965) reported that two of their largest hibernating 
colonies sampled in northwestern Texas during 1960 held 46,700 bats and 2,819 bats. During 1970, 
the number of adults of this species in Kansas was estimated at 50,000 by Kunz (1974). This num¬ 
ber is somewhat lower than estimates of “between 50,000 and 75,000 individuals” in a gypsum 
mine in the main part of the distribution in Kansas made during the mid-1960s by Dunnigan and 
Fitch (1967:11). Twente (1955a) estimated a summer population of 15,000-20,000 for south-cen¬ 
tral Kansas and northwestern Oklahoma in 1953. Reisen et al. (1976) reported a hibemaculum with 
5,000 bats of this species during winter 1972 in a gypsum cave in Harmon County, Oklahoma, and 
Caire et al. (1984) estimated a warm season colony of about 1,000 bats in Alabaster Caverns, 
Woodward County, Oklahoma during 1982, with 5,230 reported in this system during winter 1995 
(Loucks and Caire, 2007). Counts at 39 hibemacula in Oklahoma during the mid-1990s ranged 
from 0 to 39,517 individuals, with 18 caves harboring 1,000 or more hibernating bats (Loucks and 
Caire, 2007). Recent reports of a large population of cave myotis by Creecy et al. (2015) at a cave 
system in Woodward County, Oklahoma are comparable to winter population records for the same 
major hibemaculum 16 years earlier (Loucks and Caire, 2007). 
Humphrey and Oli (2015) estimated a winter metapopulation of about 20,000 cave myotis in 
their northwestern Oklahoma study area during the late 1960s and 1970s, and they suggested that 
single roosts should not be considered as individual populations because of relatively weak roost 
fidelity in their study area. Count data for the metapopulation encompassing multiple caves in 
northwestern Oklahoma showed an apparent 40% decline from 23,850 bats in winters 1967-1969 
to 14,200 in 1969-1970, then increased over a four-year period at a rate of 12.5% per year and 
apparently stabilizing at greater than 20,000 for the final three years of the study; cave flooding 
was hypothesized as a cause for the decline (see “Mortality” above; Humphrey and Oli, 2015). 
Loucks and Caire (2007) estimated numbers of bats at 39 hibemacula in Oklahoma during winters 
1994-1995 and 1995-1996 with counts at individual hibemacula ranging from zero to 39,517. 
Totals for hibemacula counted in 1994-1995 were 63,285 bats, with a total of 34,718 bats at a 
somewhat different set of hibemacula counted in 1995-1996 (Loucks and Caire, 2007). 
Sex-ratio estimates for cave myotis vary with sampling and depend on time of year, geogra¬ 
phy, and roosting patterns (Twente, 1955a; T ink le and Milstead, 1960; T ink le and Patterson, 1965; 
Hayward, 1970; Loucks and Caire 2007; Humphrey and Oli, 2015). Variation in adult sex ratios 
were reviewed in detail by Loucks and Caire (2007), Tinkle and Milstead (1960), and Tinkle and 
Patterson (1965), who examined a number of hypotheses that may account for this variation. 
Population Genetics: Estimates of mean heterozygosity based on allozyme variation at 17 
loci in 116 cave myotis sampled at two locations in Texas and a mine in Pima County, Arizona were 
high (0.144, means of separate populations ranging 0.101 to 0.163 and differing significantly 
among locations), indicating high genetic variability (Straney et al., 1976). Mitochondrial DNA 
analysis of 103 bats from Texas, Oklahoma, and the Colorado River region along the Arizona-Cal- 
ifomia border suggest high haplotype diversity (0.965 ± 0.009 SE) and somewhat low nucleotide 
diversity (0.013 ± 0.006 SE) across all regions combined, with inconclusive evidence for popula¬ 
tion bottlenecks; nuclear DNA analysis of 192 bats suggest little genetic structuring of the popula¬ 
tions sampled (Parlos, 2008). 
Management Practices and Concerns. — In California, old mines provide the only cur¬ 
rently known sites for colonies of cave myotis (Pierson et al., 1991; Altenbach and Pierson, 1995). 
Disturbance by people can lead to reductions in populations, as noted for the three mines in Ari¬ 
zona visited by researchers in the 1950’s (Hayward, 1970). In Oklahoma, Humphrey and Oli 
(2015) reported that nursery colonies of this species were much more sensitive to disturbance than 
