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PROCEEDINGS OF THE CALIFORNIA ACADEMY OF SCIENCES 
Series 4, Volume 65, Supplement I 
fomia, neither suggestive of use as a roost: one had likely become entrapped in a 23 meters tall 
tower (Huey, 1932), and a second was found hanging in a second story hallway (Huey, 1954b). One 
big free-tailed bat was taken at a building in western Colorado (Neubaum, 2017). 
Population Ecology. — Litter Size, Natality, and Female Reproduction: Eight females 
from a colony in the Chisos Mountains of Big Bend National Park in western Texas taken in 1937 
contained one embryo each (Borell, 1939). Seventeen females from elsewhere in Big Bend Nation¬ 
al Park each had a single embryo (Easterla, 1973). One female from the Chiricahua Mountains of 
southeastern Arizona and one female from the Trans-Pecos region of Texas each held single 
embryos (Cockrum and Ordway, 1959; Yancey, 1997). One female from Chihuahua, Mexico also 
had a single embryo (Bradley and Mauer, 1965). 
Twelve of 15 (80%) adult female big free-tailed bats captured in the Jemez Mountains of New 
Mexico were reproductive in 1996 and 1997 (Bogan et al., 1998). Natality in a sample of 170 adult 
females from Big Bend National Park in Texas during 1967-1971 was 85% (26 non-reproductive; 
Easterla, 1973). In a subsequent study at the park, natality was about 74% (approximately 57 of 77 
females were reproductive; Higginbotham and Ammerman, 2002). Eight of 10 adult females exam¬ 
ined by Borell (1939) in western Texas were reproductive (80% natality). Constantine (1961b) 
found 90% natality in 30 adult females examined in northern New Mexico during 1958, and LaVal 
(1973) reported that eight of 12 (67%) females taken over water in the Guadalupe Mountains 
National Park in western Texas during June were pregnant, with one of two taken in August lac- 
tating. 
Survival: We are unaware of any published literature with quantitative data on survival for 
this species. 
Mortality Factors: Mortality factors are not well known. Rabies is known in big free-tailed 
bats (for example, Constantine, 1961b; Armstrong et al., 1994; Pape et al., 1999; Mondul et al., 
2003), and they are usually infected with a rabies virus variant that is species-specific (Shankar et 
al., 2005). Eighteen moribund or dead individuals were found around pools of water at Ghost 
Ranch, near Abiquiu, New Mexico, during summer 1958; rabies was only tentatively diagnosed in 
three of the bats and cause of death of the others remained undetermined, with some pathological 
conditions of unknown etiology observed on necropsy (Constantine, 1961b). The lung fungus 
Pneumocystis has been detected in this species in Brazil (Sanches et al., 2012), as has Histoplas- 
ma capsulatum, the agent for histoplasmosis (Galvao-Dias et al., 2011). Ectoparasites have been 
reported as summarized by Sparks and Choate (2000; see also for example, Ritzi et al., 2001; 
Poche, 1981) but without evidence for associated mortality. Predation on this species in the U.S. 
has not been recorded in the literature. During summer 1997 in southeastern Utah, two of us (MAB 
and TJO) observed five peregrine falcons alight on a cliff-top above a crevice-roosting colony of 
several hundred big free-tailed bats at sunset, then repeatedly swoop among the emerging bats and 
at times were successful in capturing them. Accidental death due to ensnarement on a locust spine 
was documented at Grand Canyon National Park in Arizona (Guse, 1974). They have been found 
dead beneath wind turbines in northern Arizona (Thompson and Bay, 2012). 
Population Trend: Big free-tailed bats aggregate into maternity colonies of moderate num¬ 
bers for rearing young, but locations of breeding colonies in the United States are poorly known. 
One colony of an estimated 150 females was discovered in a horizontal crevice in a cliff in Big 
Bend National Park in 1937 (Borell, 1939); a colony of unknown size was reported to still be pres¬ 
ent at the site in 1958, thought by Davis and Schmidly (1994) to be the only known nursery colony 
of this species in the United States. This colony was not located again in subsequent attempts 
(Schmidly, 1991). A nursery colony was also suspected to exist in Guadalupe Mountains National 
Park in Texas based on the presence of 14 females (nine reproductive) and no males netted over 
