186 
PROCEEDINGS OF THE CALIFORNIA ACADEMY OF SCIENCES 
Series 4, Volume 65, Supplement I 
specimen was collected (Allen, 1864). Other English common names include Fort Yuma bat, Yuma 
bat, Gila bat, Tejon bat, and dusky bat. 
Habitats and Relative Abundance.— Yuma myotis are often found in lowland habitats 
near water, and are well known to forage along rivers, creeks, ponds and irrigation canals, usually 
close to the water surface (for example, Dalquest, 1947b; Jones and Suttkus, 1972; Hoffmeister, 
1986; Schmidly, 1991). This propensity to forage over and near water sources may bias relative 
abundance surveys based on captures in mist nets set over water. They also can be found in a vari¬ 
ety of habitat types other than lowland regions, including suburban areas (Evelyn et al., 2004), and 
over a wide range of elevations. Specimens have been taken as high as 3,353 meters on Mount 
Whitney in California (Allen, 1919). 
Pacific Northwest and Northern Rocky Mountains: Oregon, Washington, and British 
Columbia: Yuma myotis were described as “exceedingly scarce” in eastern Oregon (Whitaker et 
al., 1981:282). They ranked sixth in relative abundance (three captured among 412 individuals) out 
of eight species of night-roosting bats captured at five bridges in western hemlock forest in the 
Willamette National Forest of Oregon (Perimeter, 1996). This species ranked eighth in relative 
abundance (18 among 1,057 individuals of 11 species) of bats captured over water in the predom¬ 
inantly ponderosa pine forests of the eastern Cascade Mountains of south-central Washington 
(Baker and Lacki, 2004). They were of higher relative abundance in surveys over streams and 
ponds in Douglas fir-western hemlock forests across the western Cascades in southern Washington 
and the Oregon Coast Range, ranking fourth among 12 species (18 bats out of 241 individuals; 
Thomas, 1988). They were the most abundant (477 individuals) of 12 species captured over water 
in the semi-arid Okanagan Valley of southern British Columbia, where 958 bats were captured 
(Woodsworth, 1981). They were also the most common species (150 captures) in the same region 
during an earlier study where 351 bats of nine species were taken in nets or traps over or near water 
(Fenton et al., 1980). 
Idaho and Montana: Yuma myotis were not captured in forests of multiple types in northern 
Idaho, where 187 individuals of eight species were taken (Lacki et al., 2007). In Montana, this 
species was reported to be widely distributed only in the western part of the state (Hoffmann et al., 
1969). 
California and Nevada: Yuma myotis appear to be high in relative abundance in surveys 
completed in California. This was the most abundant species taken in mist nets set over water in 
montane hardwood/conifer habitats along the upper Sacramento River in northern California 
(Siskiyou and Shasta counties), with 654 captured among 1,398 individuals of 15 species docu¬ 
mented during 1991-1995 (Pierson et al., 1996b). They were also the highest in relative abundance 
at night roosts at bridges in this study area, where 1,919 were captured in comparison with 2,132 
individuals of nine other species (Pierson et al., 1996b). A survey based on mist netting over water 
in old growth redwood forest in the Coast Range of northern California found them highest in rel¬ 
ative abundance, with 64 captured among 142 bats of seven species (Zielinski and Gellman, 1999). 
Similarly, they were the highest ranking species in relative abundance (112 bats captured among 
403 bats of 10 species) in mist-netting surveys in Whiskeytown National Recreation Area in Shas¬ 
ta County, California, where 47 sites between 256 and 1,899 meters elevation were sampled in a 
variety of habitats, ranging from chaparral to Douglas fir forests; habitat analyses suggested that 
proximity to lakes and ponds was the most important variable associated with presence of this 
species (Duff and Morrell, 2007). 
In the wine-growing regions of Napa and Sonoma counties of northern California, echoloca- 
tion activity of this species was high compared to most others, particularly in habitats with remnant 
vegetation (riparian forest, oak woodland, eucalypt groves) around vineyards rather than in the 
vineyard interiors (Kelly et al., 2016). Echolocation activity of Yuma myotis was the second high- 
