86 
PROCEEDINGS OF THE CALIFORNIA ACADEMY OF SCIENCES 
Series 4, Volume 65, Supplement I 
Riverside Mountains of California included many forms that were taken on the ground or from the 
surfaces of vegetation, including orthopterans (grasshoppers and crickets), noctuid moths and 
caterpillars, and scarab and carabid beetles (Vaughan, 1959); they will also alight on ceilings of 
grottos, caves, and abandoned mines to manipulate and consume larger prey items such as sphinx 
moths, grasshoppers, and beetles (Huey, 1925; Vaughan, 1959; Ross, 1964). 
Ross (1964, 1967) examined 41 digestive tracts from individuals taken in both Arizona and in 
Mexico. Typical insect prey sizes ranged 40 to 60 millimeters and the bats primarily consumed the 
abdomens of the larger prey items. However, smaller items ranging down to 20 millimeters were 
also noted, including flying ants. As in California, prey included large slow-flying insects and 
mainly terrestrial species such as sphinx moths, short-horned and long-homed grasshoppers (Acri- 
didae and Tettigoniidae), long-homed beetles (Cerambycidae), and caterpillars. Ross (1964) also 
reported that stomachs of these bats contained fruit or other vegetative matter, but these specimens 
were likely M. waterhousii taken in Mexico prior to a revised understanding of the systematics of 
Macrotus. Food items summarized from the literature by Bradshaw (1961) included coleopterans 
(Carabidae, Meloidae, and Scarabaeidae), orthopterans (including grasshoppers), lepidopterans 
(Sphingidae, Noctuidae, Cossidae, and caterpillars), odonates (dragonflies), homopterans 
(cicadas), dipterans, and hymenopterans. Other reports of prey include cockroaches and diurnal 
acridid grasshoppers and nymphalid butterflies (Bell et al., 1986), as well as small lizards (Brown, 
2013). Many of these prey items were probably taken from the ground or surfaces of vegetation 
(Vaughan, 1959; Bradshaw, 1961; Bell, 1985). 
California leaf-nosed bats have echolocation characteristics that are well suited for foraging in 
the cluttered situations encountered by species that glean prey from vegetation and ground surfaces 
(low intensity, high frequency, and short duration ultrasonic pulses), particularly in total darkness; 
they will also cue on audible sounds made by prey (Bell 1985). However, vision is very well devel¬ 
oped compared to many other insectivorous bats, and they regularly interrupt echolocation and 
switch to vision to locate insects, particularly under moonlight conditions (Bell, 1985; Bell and 
Fenton, 1986). 
Renal structure suggests that California leaf-nosed bats have good urine concentrating ability, 
consistent with their distribution in arid habitats, and they can persist in the laboratory for six 
weeks without access to drinking water (Lu and Bleier, 1981). Nonetheless, their maneuverability 
close to the ground also allows them to access small surface areas of water when available (Tay¬ 
lor, 2007). They regularly drink at such sources in southern Arizona, particularly females during 
lactation (Schmidt, 1999). 
Roosting Habits. — California leaf-nosed bats roost in abandoned min es and caves in the 
Desert Southwest, generally at elevations less than 762 meters (for example, Grinnell, 1918; How¬ 
ell, 1920a; Brown et al., 1993a,b; Cockrum et al., 1996). Currently all known winter and materni¬ 
ty colonies in California are located in old mines, with the exceptions of two maternity colonies of 
10 or fewer individuals in shallow caves (Brown, 2013). Most roosts reported from Arizona are in 
mines, although several caves are also used (Schmidt, 1999). This species has been characterized 
as an obligate user of abandoned mines in much of their range, and it has been suggested that their 
distribution may have expanded in response to the appearance of abandoned mines on the land¬ 
scape (Bradshaw, 1961; Altenbach and Sherwin, 2002). Some caves and mines used as roosts are 
shared with several other species of bats (see for example, Bradshaw, 1961; Brown, 2013). 
Winter Roosts: California leaf-nosed bats require warm roost temperatures of about 23 to 
27°C or higher and do not drop body temperatures to very low levels or hibernate (Bradshaw, 1961; 
Bradshaw, 1962; Bell et al., 1986; Brown and Berry, 1991). However, this species can be some¬ 
what heterothermic during winter and can reduce body temperature to about 26°C and appear 
