70 
PROCEEDINGS OF THE CALIFORNIA ACADEMY OF SCIENCES 
Series 4, Volume 65, Supplement I 
tracts of nine additional individuals from Arizona showed predominantly large (60 millimeters) 
sphinx moths as prey (abdomens only), although ingesta also included leafhoppers, other 
homopterans, a cicada, and a planthopper (Fulgoridae; Ross, 1964, 1967). Easterla and Whitaker 
(1972) also reported large moths as predominant food items, constituting about 80% of the volume 
in stomachs of 18 bats collected in Big Bend National Park in Texas during 1971, but also noted 
the occasional presence of crickets and grasshoppers. 
Roosting Habits. — Early researchers found the first known roosts of these bats in the Unit¬ 
ed States in buildings in southern California (Stephens, 1906; Grinnell, 1918; Howell, 1920b). 
Although Howell (1920b) found colony sizes numbering 13-70 individuals roosting in buildings 
in this region, he suspected that their natural proclivity was to roost in rock crevices or cavities in 
high limbs of trees. Since then, natural roosts of Eumops perotis found in the U.S. primarily have 
been located in deep crevices in cliffs and rock outcrops, with colony sizes generally small and 
within the range noted by Howell (1920b). Roosts described in California in the 1930’s to 1950’s 
were in vertical crevices in granite or sandstone cliffs, with openings more than 4.5 meters above 
bases and varying in width from seven to 45 centimeters (Dalquest, 1946; Krutzsch, 1955). 
Colonies make considerable chattering and squawking sounds from within roosts during warmer 
parts of the day (for example, Krutzsch, 1955; Vaughan, 1959). Numbers of greater bonneted bats 
using any particular roost can vary from day to day and shifting of roost sites within local areas has 
been reported (Krutzsch, 1955; Ohlendorf, 1972), although some roosts are often occupied year 
after year (Krutzsch, 1955). One roost along the Kern River in central California that held an esti¬ 
mated 100 bats in 1948 was documented with about 75 bats in 1994, and a roost in San Diego 
County that was occupied in 1937 appeared to be used in 1991, indicating long-term occupancy 
(Pierson and Rainey, 1998c). Females with young are known to occupy roosts simultaneously with 
adult males (Howell, 1920b). Other species of bats often roost in the same or nearby crevices. Soli¬ 
tary individuals, presumed wanderers or stragglers, have been observed on trees, sides of buildings, 
under awnings and in other atypical, temporary situations (von Bloeker, 1932; Krutzsch, 1955). 
Little is known about seasonal differences in roost utilization, but these bats are not known to 
undergo deep winter hibernation (Leitner, 1966). Greater bonneted bats are very active and alert 
within roosts during warmer months in California, where during December through February they 
are known to enter daily torpor and arouse in the evenings to emerge and feed nightly, except on 
cool nights when air temperature was below 5°C (Leitner, 1966). Howell (1920b) observed shal¬ 
low torpor in this species and reported that the bats could remain torpid in their roosts for several 
days during extended periods of cool winter weather in southern California. Although some roosts 
may be used year-round, there is also evidence for some switching from summer roosts to other 
locations during winter (Krutzsch, 1955). 
Openings to rock crevices used as roosts can be horizontal or vertical (Krutzsch, 1955). 
Because of their low maneuverability and fast flying speed, they occupy crevices with unobstruct¬ 
ed approaches and openings high above ground (Howell, 1920b; Krutzsch, 1955; Vaughan, 1959). 
Well-used colony sites are marked by urine stains on cliff faces and accumulations of guano below. 
In an extensive study in California, Vaughan (1959) found these bats in 22 such crevices, all of 
which were vertical, nearly vertical, or situated on steep slopes. Crevices used as roosts were more 
than 0.3 meters deep and usually more than three meters deep, with entrances at least five cen¬ 
timeters wide and 15 centimeters long at the bottoms or sides of the crevices. Most of these were 
in large, exfoliating slabs of rock in granite or consolidated sandstones. Similarly, in southwestern 
Texas a colony of 71 greater bonneted bats roosted in a high crevice formed by exfoliating rimrock 
(Ohlendorf, 1972). 
The only two roosts known in Arizona in the early 1960’s were maternity colonies in widely 
separated parts of the state. One housed 15-20 bats in an up to 12-centimeter-wide crevice in the 
