O’SHEA, CRYAN & BOGAN: UNITED STATES BAT SPECIES OF CONCERN 
53 
C. townsendiipallescens documents declines. Surveys were conducted in California during the late 
1980s and early 1990s that emphasized comparisons with historically occupied sites (based on 
records from the 1940s to 1960s). This work indicated that over an approximately 40-year period 
there was a 52% loss in the number of maternity colonies (24 of 46), a 55% decline in total num¬ 
bers of adult females (from 3,004 to 1,365 at 18 maternity sites), a 44% decline in the number of 
available roosts, and a 32% decrease in average size of remaining colonies (Pierson and Rainey, 
1998a). Bats in the area of a maternity site numbering 140 and a hibemacula of 65 studied by Pear¬ 
son et al. (1952) in 1949-50 in northern California had declined to about 70 and 26, respectively, 
in 1987-88; a maternity colony numbering about 200 bats in the 1960’s in a separate area in the 
same region appeared to be reduced to about 150 in 1987 (Pierson et al., 1991). Overall, four hiber¬ 
nation sites in California studied by Pearson et al. (1952) that housed a total of 470 bats held just 
59 individuals in the late 1980s and early 1990s (Pierson and Rainey, 1998a). Numbers of hiber¬ 
nating bats at two sites in Lava Beds National Monument in California remained at about 30 
between 1949 and 1988. In coastal California, only seven small colonies were known for 
C. townsendii townsendii in 1989, with just three actively protected (Pierson, 1989). 
The survey report for California (Pierson and Rainey, 1998a) also summarized unpublished 
information and reports from investigations by others on the status of this species in some other 
western states. These other studies also document declines, albeit frequently anecdotal and subject 
to bias. Major declines were noted at sites in Oregon and Washington. Intensive surveys for mater¬ 
nity colonies over large areas in Nevada revealed only two sites with small groups. Four hibemac¬ 
ula in Idaho experienced a 60% decline since 1987. As noted above, a group of more than 10,000 
hibernating in a mine in New Mexico was reduced by several thousand after vandals burned the 
site during winter (Pierson and Rainey, 1998a; Pierson et al., 1999). Subsequent gating at mine 
entrances at the complex of mines involved suggested that some recovery had occurred (Kretz- 
mann, 2000). In Arizona, two historically known populations in caves had disappeared, and anoth¬ 
er with historical estimates of several hundred adult females dropped to less than 100 (Pierson and 
Rainey, 1998a). A mine in the Hualapai Mountains of Arizona that served as a hibemaculum for 
1,500 bats in 1962 held about 100 bats in 1997-1998 (Brown and Berry, 1999). An increase in 
abundance between 1972 and 1997 at one site in Arizona occupied by a small colony of breeding 
females was reported by O’Shea and Vaughan (1999), who suggested that the 1997 numbers 
remained below those presumed present when mammalogists first visited the site in 1931. Mist- 
netting surveys over a small desert spring in southern Nevada found this species to be equally rare 
between two sampling periods separated by about 50 years (O’Farrell and Bradley, 1970; O’Shea 
et al., 2016b). 
Population estimates for both subspecies considered species of concern are not available over 
the entire range. However, past estimates have been made in some areas which may be useful for 
trend comparisons in the future. A gross estimate of 11,000 C. townsendii pallescens over the 
southern Great Plains (Kansas, Oklahoma and Texas), thought likely to be biased upwards, was cal¬ 
culated by Humphrey and Kunz (1976) for the early 1970’s. In Kansas, the population is centered 
in the south-central part of the state. A summer population of 300 to 500 was estimated by Twente 
(1955a) for south-central Kansas and adjacent areas in Oklahoma. The total number of adult 
females at 38 maternity colonies in California in the late 1980s-early 1990s was 4,250 (Pierson and 
Rainey, 1998a). Other unpublished information summarized by Pierson and Rainey (1998a) indi¬ 
cated that in 1990 about 2,700 adult females occurred at known sites in Oregon, and about 800 
adult females occupied known sites in Washington. A large maternity colony was observed as a 
cluster of about 100 (90 taken in one attempt with a hand net) at a cave in eastern Washington in 
1929 (Scheffer, 1930), and a maternity colony of about 200 was observed in an abandoned mine at 
