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PROCEEDINGS OF THE CALIFORNIA ACADEMY OF SCIENCES 
Series 4, Volume 65, Supplement I 
been long known by naturalists that whereas males may use higher elevations, females of several 
species of western bats tend to use lower elevations to form maternity colonies (for example, How¬ 
ell, 1920a). Warmer temperatures at lower elevations are more favorable for rapid growth and 
development of young, whereas cooler temperatures at higher elevations can allow deeper daily 
torpor for males and non-reproductive females (for example, Cryan et al., 2000; Bogan and Moll- 
hagen, 2016; see review in Weller et al., 2009). Males and non-reproductive females tend to be 
found in higher proportions at higher elevations. Elevational differences in distribution of the sexes 
for fringed myotis were reported for the Black Hills of South Dakota, where captures at upper ele¬ 
vations were disproportionately males and non-reproductive females with reproductive females 
more often captured at lower elevations (Cryan et ah, 2000). In Badlands National Park, South 
Dakota, 24 of 29 (83%) captured at multiple sites were males (Bogan et ah, 1996). Cockrum et ah 
(1996) reported that these bats separate into male colonies and female colonies in summer in 
Mohave County, Arizona, with male colonies at higher elevations. 
In the Cibola National Forest of New Mexico, Chung MacCoubrey (2005) found a significant 
effect of elevation on probability of capturing reproductive female fringed myotis compared to 
non-reproductive females and males, with a higher proportion of reproductive females in summer 
in the lower elevation (2,133 to 2,573 meters) pinon-juniper dominated Gallinas Mountains than in 
the higher elevation (2,347 to 2,682 meters) ponderosa-pine dominated San Mateo Mountains. 
Geluso and Geluso (2012) reported that 121 of 126 individuals captured during 19 years of netting 
in ponderosa pine/mixed pine forests at elevation 2,573 meters in the San Mateo Mountains of New 
Mexico were adult males. Hayes and Adams (2014) compiled 729 capture and occurrence records 
for this species in Colorado, mapped the records, and analyzed a subset of these data (546 records) 
for patterns by sex, reproductive status, and elevation. Mean elevations of reproductive females and 
juveniles were similar at 1,862 and 1,843 meters with similar confidence intervals; these confi¬ 
dence intervals did not overlap those for the higher mean elevations of records for non-reproduc¬ 
tive females (1,976 meters) and males (2,003 meters non-reproductive males, 1,941 meters repro¬ 
ductive males; Hayes and Adams, 2014). (Records were available from 23 of 64 counties in Col¬ 
orado that encompassed a variety of habitats, although 408 of the 729 records were based on inten¬ 
sive sampling in Boulder County [Hayes, 2011]). 
Foraging and Dietary Analysis. — The foraging flight of fringed myotis has been 
described as “fluttering and soaring” (Dalquest and Ramage, 1946:60). Echolocation detectors 
tethered to helium balloons demonstrated foraging activity at canopy height (detectors placed at 67 
meters within canopies ranging to 82 meters) in groves of giant sequoias in Yosemite National 
Park, California (Pierson et al., 2006). 
Results of dietary analysis seem to vary by study area. Fringed myotis were classified as pos¬ 
sible beetle strategists and between-, within-, and below-canopy foragers in dietary analysis of bats 
sampled in the San Mateo Mountains of New Mexico (Black, 1974). Beetles were also the highest 
in frequency of occurrence in fecal samples from northern Arizona ponderosa pine forests, fol¬ 
lowed by moths and dipterans, but they also fed opportunistically on swarms of homopterans 
(Warner, 1985). In riparian areas in the Oregon Coast Range, this species had a varied diet, eating 
primarily spiders, lepidopterans, homopterans, and coleopterans in descending order by propor¬ 
tional volume, but also consuming insects in a variety of other groups including dipterans, 
hemipterans, neuropterans, and orthopterans (Ober and Hayes, 2008). In northeastern Oregon, the 
diet consisted primarily of lepidopterans and to a lesser extent homopterans and other groups 
(Whitaker et al., 1981). Similarly, dietary analysis of stomach contents of individuals from north¬ 
western Colorado indicated that lepidopterans were the major dietary component, followed by tri- 
chopterans and coleopterans in descending order of proportional frequency, with other groups of 
insects each constituting less than 10% (Armstrong et al., 1994). 
