O’SHEA, CRYAN & BOGAN: UNITED STATES BAT SPECIES OF CONCERN 
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of banded individuals were near the site where they were originally banded (Cockram et al., 1996). 
Surveys of regional bat faunas in mist nets set over water have seldom reported this species, per¬ 
haps because the bats are restricted in roosting and foraging habits, generally do not disperse far 
from roosts, and are maneuverable fliers that readily avoid capture (see below). 
Arizona: California leaf-nosed bats occur primarily in Sonoran desert scrub in Arizona, where 
they probably do not make extensive seasonal movements to other habitats (Hoffmeister, 1986). In 
northwestern Arizona and adjacent areas, 1,667 of these bats were banded from 1959-1964 (Cock- 
rum et al., 1996). Although large samples were banded at about nine roosts in western Arizona as 
noted above, they were not taken over water at multiple locations in the same region, despite cap¬ 
tures of 3,458 individuals of 17 other species (Cockram et ah, 1996), nor during later mist netting 
or acoustic surveys (Brown and Berry, 1999). None were documented in the Arizona Strip of 
extreme northwestern Arizona despite previous records and 1,175 captures of 17 other species 
(Herder, 1998). At Kofa National Wildlife Refuge in southwestern Arizona, the California leaf¬ 
nosed bat ranked lowest in relative abundance of six species documented drinking at small artifi¬ 
cial water sources in lower Colorado River Sonoran and Arizona Upland Sonoran desertscrab veg¬ 
etation types, with 18 individuals captured among 427 bats (Rabe and Rosenstock, 2005). A major 
exception to rarity in surveys occurred after targeted mist netting for this species over four small 
artificial water sources in Sonoran desertscrab habitat at Cabeza Prieta National Wildlife Refuge in 
southwestern Arizona at the Mexican border, an area in close proximity to abandoned mines that 
housed colonies of this species (Schmidt, 1999). This was the most abundant species taken at this 
study area, with 470 bats captured among 1,153 bats of nine species documented on 68 nights of 
netting in all seasons during three calendar years (Schmidt, 1999). 
California: Grinnell (1918:255) stated “In California, the leaf-nosed bat seems to be confined 
to the hottest parts of the Lower Sonoran zone, mainly on the Colorado Desert.” Although some¬ 
what more widespread in southern California in the past (Constantine, 1998a), habitats used by 
these bats in California are now limited to deserts in southeastern California, primarily in moun¬ 
tain ranges along the lower Colorado River (Brown, 2006). Natural history observations in Cali¬ 
fornia suggest that these bats utilize lower elevation desert habitats near preferred roosting sites in 
caves and abandoned mines, with foraging concentrated in desert washes and surrounding areas or 
over the river floodplain (Vaughan, 1959; Brown and Berry, 1991; Brown et al., 1993a,b). 
Nevada: Differential use of habitat types within riparian areas in the Mojave Desert of south¬ 
ern Nevada by these bats was studied primarily using acoustic detections: California leaf-nosed 
bats occurred in each of four habitats (riparian marsh, mesquite bosque, riparian woodland, and 
riparian shrabland) about equally (Williams et al., 2006). 
Foraging and Dietary Analysis. — These bats forage in desert habitats and seem to favor 
desert washes, at least during the warmer months, where they glean insects from riparian vegeta¬ 
tion and the ground (Brown and Berry, 1991; Schmidt, 1999). Taking prey from the ground was 
first suggested by Hilda Grinnell (1918) who noted the capture of a California leaf-nosed bat in a 
mouse trap in 1908 and speculated that it was attracted to insects feeding on the bait. Banding and 
radio-tracking studies in the Cargo Muchacho Mountains of southeastern California have shown 
that in the area studied, these bats rarely travel more than five to ten kilometers from their roosts 
and forage primarily in desert washes where they were observed feeding on large moths and katy¬ 
dids (Brown et al., 1993a,b). 
Vaughan (1959) described the flight of these bats as extremely maneuverable and rapid, but 
noted that while foraging their flight can be slow, buoyant, nearly silent, and will include hovering. 
Individuals watched while foraging flew within one meter of the ground, often dropping closer, and 
also foraged close to vegetation (Vaughan, 1959). Stomach contents of these bats taken in the 
