O’SHEA, CRYAN & BOGAN: UNITED STATES BAT SPECIES OF CONCERN 
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sonal, from April to October. However, subsequent research found these bats present in the region 
during mid-winter (Petryszyn and Cockrum, 1990). 
Two subspecies of Underwood’s bonneted bat are recognized. Eumops underwoodi sonorien- 
sis (first named as Eumops sonoriensis by Benson [1947] based on specimens from Sonora) is 
found in southern Arizona and Sonora, Mexico. Eumops underwoodi underwoodi occurs from Chi¬ 
huahua, Mexico south to Nicaragua. Distribution and systematic s are reviewed in greater detail by 
Kiser (1995) and Eger (1977), with a complete taxonomic synonymy of past scientific names 
applied to Underwood’s bonneted bat appearing in Kiser (1995). The generic name Eumops comes 
from the Greek word meaning “good” and the Malay word meaning “bat”. The specific epithet is 
a patronym in honor of Cecil F. Underwood, collector of the type specimen taken in Honduras in 
1937 (Goodwin, 1940). Other English common names include Underwood’s mastiff bat. 
Habitats. — In the United States, this bat is known only from near the boundary with Mexi¬ 
co in Pima County, Arizona (Hoffmeister, 1986). They have been taken in mist nets while drinking 
at a number of watering sites, catchment basins, and reservoirs in Sonoran Desert and mesquite- 
grassland habitats. Like other molossid bats, this species is probably capable of traveling long dis¬ 
tances to forage, and they may migrate. In Arizona, specimens have been taken in mesquite bosque 
habitat (Cockrum and Gardner, 1960) near Sasabe and over Quitobaquito Pond in Sonoran desert 
scrub at Organ Pipe Cactus National Monument in all seasons (Petryszyn and Cockrum, 1990). 
Foraging habitats are noted below. In Jalisco, Mexico, they have been reported from pine-oak 
forests (Watkins et al., 1972), and they are also found in a variety of other habitats in the Neotrop¬ 
ics, including tropical forest (Carter et al., 1966; Hellebuyck et al., 1985). 
Foraging and Dietary Analysis. — Underwood’s bonneted bats make loud, piercing, high- 
pitched audible calls while in flight. Three radio-tagged individuals captured at Quitobaquito Pond 
in Organ Pipe Cactus National Monument in Arizona foraged nightly over relatively flat areas of 
the Rio Sonoyta Valley and adjacent bajadas and slopes, and into the city of Sonoyta, Mexico, a 
maximum of 24 kilometers from day roosts; general observations suggested flight paths covered 
hundreds of kilometers per night while foraging (Tibbitts et al., 2002). Foraging habitats included 
Sonoran desertscrub, mesquite-tamarisk riparian areas, agricultural fields, wilderness, and residen¬ 
tial areas; bats also foraged over steep terrain along ridgelines and hilltops (Tibbitts et al., 2002). 
The bats did not return to Quitobaquito Pond for water each night, presumably drinking at other 
sources around Sonoyta such as the large sewage treatment plant. Over the approximately five- to 
13-night tracking periods of the three bats, nightly home range estimates varied from 1.0 to 284.6 
square kilometers and estimated foraging areas were 100, 160, and 474 square kilometers (Tibbitts 
et al., 2002). 
Morphological specializations of the head and limited information on food habits suggest that 
this species feeds primarily on beetles (Freeman, 1979). Ross (1964) reported six- to 10-millime¬ 
ter beetles as the predominant food item (47%) in digestive tracts of 6 bats collected at one loca¬ 
tion on the same night in Arizona, but also noted the presence of large orthopterans (40-60 mm) at 
31%, homopterans (cicadellids), and lepidopterans. One specimen from Michoacan, Mexico had 
fed on large {ca. 40-60 millimeters) June beetles and long-homed beetles, suggesting that the diet 
of Underwood’s bonneted bat can include a diversity of types and sizes of insects (Ross, 1967). 
Roosting Habits. — Roosting sites in the U.S. remained undescribed for nearly 50 years 
after these bats were first discovered in Arizona. It had previously been speculated that they may 
roost in crevices in high steep cliffs (for example, Hoffmeister, 1986), similar to other molossid 
bats. However, in Jalisco, Mexico, a group of 13 was reported roosting in a large hollow tree 
(Watkins et al., 1972) and an individual was reported roosting under palm leaves in El Salvador 
(Hellebuyck et al., 1985). In 2001, preliminary radio-tracking studies of three individuals con- 
