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PROCEEDINGS OF THE CALIFORNIA ACADEMY OF SCIENCES 
Series 4, Volume 65, Supplement I 
handle near the Cimarron River (Glass and Ward, 1959: Roehrs et al., 2008), where they were 
thought to be the most common species of Myotis in pinon-juniper woodlands (Dalquest et al., 
1990). They are not known from Great Plains states north of Oklahoma (Braun et al., 2015) but 
conceivably could occur along the Cimarron River where it runs through Kansas (Sparks and 
Choate, 2000). 
Elevational Differences in Habitats among Sex and Age Classes: At Big Bend National 
Park in Texas, only male Yuma myotis were taken above about 2,000 meters (Easterla, 1973). Dis¬ 
proportionate use of higher elevations by males also has been suggested for California (based on 
limited data; Allen, 1939, Dalquest, 1947b) and British Columbia (Fenton et al., 1980). In western 
Colorado, proportions of males and females did not noticeably vary by elevation; most captures of 
both sexes were at lower elevations close to permanent water sources (Neubaum, 2017). 
Foraging and Dietary Analysis. — Yuma myotis are often observed flying close to the 
surface of water (for example, Dalquest, 1947b; Glass and Ward, 1959; Fenton et al., 1980). Indi¬ 
viduals observed as they emerged from a California roost flew directly to the nearby Truckee River 
within 10 meters of the ground, skimming over tops of low trees and feeding for several minutes 
before drinking (Dalquest, 1947b). Hunting flights over pools were described as in a straight direc¬ 
tion, but “with innumerable dips and swerves of from a few inches to six feet in one direction or 
another” (Dalquest, 1947b:241). Individuals were noted as flying within one meter of the surface 
of the water in southern British Columbia but favored feeding over slower stretches of flowing 
water, river banks, and near the canopies of trees in comparison with sympatric little brown myotis 
(M. lucifugus\ Fenton et al., 1980). Quantitative observations (also in southern British Columbia) 
show that they spend less time foraging in areas with structurally complex vegetation, regardless 
of reproductive condition or age class, instead spending most of their foraging time over water, in 
open areas within 10 meters of the ground, and close to trees (Herd and Fenton, 1983; Brigham et 
al., 1992). Nonetheless, they also have been observed feeding low to the ground within dense 
willow thickets and other thick vegetation (Dalquest, 1947b), consistent with the maneuverability 
suggested by their wing morphology (Aldridge, 1986; Brigham et al., 1992). In northern Califor¬ 
nia, echolocation activity of foraging bats was higher in areas of remnant vegetation (riparian 
forest, oak woodland, eucalypt groves) around vineyards than in the vineyard interior (Kelly et al., 
2016). Distances moved both within nights and between seasons is not well understood for this 
species. Yuma myotis in western Colorado moved an average of one kilometer between capture 
sites and the first roost used after being radio tagged (Neubaum, 2017), although one pregnant 
female moved nearly 40 kilometers in just two nights after being fit with a radio, demonstrating 
that longer movements are possible. 
Reported foods include small insects such as moths, but also include those with aquatic phas¬ 
es to the life cycle, particularly caddis flies, mayflies, and dipterans (including midges), many like¬ 
ly taken over water (Easterla and Whitaker, 1972; Whitaker et al., 1977; Herd and Fenton, 1983; 
Brigham et al., 1992). However, observations of this species foraging on swarms of ephemeral fly¬ 
ing ants (Pogonomyrmex sp.) emerging along a cliff face (Vaughan, 1980) and their responses to 
artificial patches of prey created by black lights (Fenton and Morris, 1976) suggest that they can 
be opportunistic feeders. Under some conditions they can fill their stomachs within 15 minutes 
after dusk (Dalquest, 1947b). In riparian areas in the Oregon Coast Range, they had a varied diet 
of small insects, eating primarily dipterans, trichopterans, isopterans, lepidopterans, and spiders in 
descending order by proportional volume, but they also consumed insects in a variety of other 
groups including coleopterans, hemipterans, hymenopterans, and neuropterans (Ober and Hayes, 
2008). In northeastern Oregon, they were reported to feed across a variety of insect groups, includ¬ 
ing lepidopterans (most abundant at 23% volume), coleopterans, trichopterans, homopterans, 
