O’SHEA, CRYAN & BOGAN: UNITED STATES BAT SPECIES OF CONCERN 
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been found to be nearly undetectable by many sympatric nocturnal moths (Fullard and Dawson, 
1997) and are consistent with a long-range prey detection strategy and the observed habits of for¬ 
aging over open places (Woodsworth et al., 1981; Storz, 1995). 
Leonard and Fenton (1983) observed spotted bats foraging during 1981 in the Okanagan Val¬ 
ley of southern British Columbia. The bats spent most of their foraging time over old fields and 
hay meadows that were near ponderosa pine forests, but they only used the forest or burned forest 
for commuting, and seldom foraged over open river or orchards (other observations in the region 
suggested that open ponderosa pine woodlands were also used for foraging [Woodsworth et al., 
1981; Wai-Ping and Fenton, 1989]). The bats foraged about 68% of the time in long (40 to 70 
meters) elliptical orbits about 10 meters above ground, but at other times they used less predictable 
patterns (Leonard and Fenton, 1983). Foraging periods were variable and ranged from 11.6 ± 10.6 
(presumed SD) min in May to 6.8 ± 5.3 (presumed SD) min in August; bats often dove within one 
meter of the ground while chasing prey but were never seen gleaning (Leonard and Fenton, 1983). 
Foraging activity was not strongly affected by moonlight (Leonard and Fenton, 1983; Wai-Ping and 
Fenton, 1989). 
Spotted bats in British Columbia were calculated to attack insects every 44.5 s, with an esti¬ 
mated 87.5% success rate (Wai-Ping and Fenton, 1989). Three radio-tracked adult females in 
southern British Columbia returned to individual foraging areas via the same commuting corridors 
each night for four to nine nights of continuous tracking in 1986-1987, and foraging areas over¬ 
lapped among individuals (Wai-Ping and Fenton, 1989). These bats flew continuously during for¬ 
aging with no evidence of gleaning and only stopped during downpours. Foraging areas were ellip¬ 
tical in shape, 200-300 meters long, and at heights of five to 15 meters above ground; times of 
returning to the roost after foraging were variable, but emergence times showed little variability. 
Foraging areas were more predictable from night to night during early to mid-summer than during 
early August and later (Wai-Ping and Fenton, 1989). 
Foraging spotted bats sometimes reacted seemingly aggressively to playbacks of recordings of 
calls of other bats but not to playbacks of other sounds (Leonard and Fenton, 1984). These and 
other preliminary observations of foraging bats indicated to several investigators that these bats 
feed solitarily and may defend boundaries of foraging areas with agonistic vocalizations if other 
spotted bats approach within about 50 meters (Woodsworth et al., 1981; Leonard and Fenton, 1983, 
1984; Storz, 1995). Although mutual avoidance and solitary foraging is well supported by obser¬ 
vations, there is little evidence for true foraging territoriality centered on specific locations, and 
some investigators have reported several individuals sometimes sharing a foraging area (Wai-Ping 
and Fenton, 1989; Navo et al., 1992; Pierson and Rainey, 1998b; Chambers et al., 2011; see above). 
Ross (1961) examined 18 guano pellets and found no prey items other than lepidopterans, with 
remains of 21 moths estimated to be about eight to 12 millimeters in length. Ross (1964,1967) fur¬ 
ther examined stomach contents of five bats from New Mexico collected by Clyde Jones and again 
only detected moths, at an estimated size range of five to 11 millimeters. Eighteen fecal pellets 
from six individuals captured in New Mexico during 2006 had 97.5% lepidopterans by propor¬ 
tional volume (Geluso 2006,2017). Two stomachs of bats collected by mist net over water at 2,300 
meters elevation in southern Utah contained only remains of moths about 10 millimeters in size 
(Easterla, 1965). Moths constituted 97% of prey volume in stomach contents of 15 bats collected 
at Big Bend National Park in Texas during 1971, with two bats also containing adult June beetles 
(Easterla and Whitaker, 1972). Lepidoptera were also predominant in stomach contents of eight 
bats from southern Utah (Poche, 1981). A small sample of fecal pellets of bats sampled in south¬ 
ern British Columbia also consisted mainly of lepidopterans, with one small beetle also noted (Wai- 
Ping and Fenton, 1989). A spotted bat released during daylight was observed dropping to the 
ground and capturing a grasshopper (Poche and Bailie, 1974). 
