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PROCEEDINGS OF THE CALIFORNIA ACADEMY OF SCIENCES 
Series 4, Volume 65, Supplement I 
firmed that bats captured drinking at the Quitobaquito Pond at Organ Pipe Cactus National Monu¬ 
ment in Arizona roosted in secondary cavities (previously formed by an excavating animal like a 
woodpecker) in large saguaro cacti (Tibbitts et al., 2002; Tibbitts and Pate, 2009). The first roost 
found in 2001 was in a woodpecker-excavated cavity near the top of a nine-meter tall saguaro 
where one radio-tagged bat and two untagged bats emerged at dark. Subsequently the three tagged 
bats were observed resting during the day in separate cavities, often switching cavities from day to 
day; cavities used by any one individual were all generally within one kilometer of each other. 
Numbers of bats using any particular cavity varied from one to five. Underwood’s bonneted bats 
also used woodpecker cavities in saguaros for night roosting (Tibbitts et al., 2002). 
Population Ecology.— Litter Size, Natality, and Female Reproduction: One Under¬ 
wood’s bonneted bat taken in extreme southern Arizona had a single embryo, and all of eight adult 
females taken over water in July 1958 were reproductive (Cockrum and Gardner, 1960). Another 
female was also reported with a single embryo (Hoffmeister, 1986). One of two (50%) adult 
females taken in southern Arizona during May 1959 was reproductive and gave birth to a single 
young in captivity (Constantine, 1961a). Nine female E. underwoodi underwoodi captured over 
water in Nicaragua were all reproductive (Dolan and Carter, 1979). 
We are unaware of any other detailed published information on additional aspects of the pop¬ 
ulation ecology of Underwood’s bonneted bat. 
Management Practices and Concerns.— The maintenance of water sources known to be 
relied on for drinking within the limited range in the U.S. appears to be critical. These bats are 
believed to need large surface areas for access to drinking water due to lack of maneuverability, so 
that loss of water at Quitobaquito Pond and other sources of drinking water with large surfaces 
within their limited U.S. distribution (for example, around the Baboquivari Mountains) could be 
very detrimental. Over-collecting at these sites by biologists should be guarded against. Increasing 
human encroachment and expanded vehicular traffic near Quitobaquito Pond on Organ Pipe Cac¬ 
tus National Monument also is a major concern. They have been observed feeding low over the 
expanding nearby highway (Tibbitts et al., 2002). Deaths due to collisions with motor vehicles are 
gaining increasing attention as a source of mortality in bats (for example, O’Shea et al., 2016a). 
Idionycteris phyllotis — Allen’s big-eared bat (Family Vespertilionidae) 
Conservation Status. — National and International Designations: U.S. Fish and Wildlife 
Service (1994, 1996a,b): Species of Concern (inactive, former Category 2 candidate for listing 
under the U.S. Endangered Species Act). Bureau of Land Management (2009a, 2010c, 2011a,b, 
2017): Sensitive Species (Arizona, Colorado, Nevada, New Mexico, Utah state offices). Interna¬ 
tional Union for the Conservation of Nature (2017): Least Concern. NatureServe (2017): Rounded 
Global Status G4, Apparently Secure. 
State Designations: Arizona Game and Fish Department (2012): Tier IB Species of Greatest 
Conservation Need. Colorado Parks and Wildlife (2015b): Species of Greatest Conservation Need, 
Tier 2. Nevada Department of Wildlife (2013): Protected Mammal, Species of Conservation Prior¬ 
ity. Nevada Department of Conservation and Natural Resources (2015a): Critically Imperiled. New 
Mexico Department of Game and Fish (2006, 2015): Imperiled, Species of Greatest Conservation 
Need, Sensitive. Utah Division of Wildlife Resources (2015; Sutter et al., 2005): Species of Great¬ 
est Conservation Need. 
Description.— Allen’s big-eared bat (Fig. 17) is distinctive among U.S. bats with long ears: 
it has a pair of lappets, or fleshy lobes, extending from the base of the ears to over the forehead, 
and lacks conspicuous glands on the muzzle. The calcar is keeled. Forearm lengths range from 42 
to 49 mm and body masses 8 to 16 g (Czaplewski, 1983; Hoffmeister, 1986). Pelage coloration is 
