208 
PROCEEDINGS OF THE CALIFORNIA ACADEMY OF SCIENCES 
Series 4, Volume 65, Supplement I 
widely in relative abundance among surveys and regions. A final category of “other” was used for 
three species of western bats that do not rank high in relative abundance in surveys, and that have 
local distributions dependent on the distributions of caves or old mines over a variety of habitats 
in two cases (Townsend’s big-eared bat and cave myotis) and on undefined factors in the case of 
the third and little-studied species (Allen’s big-eared bat). 
Foraging and Dietary Analysis. — The different species of concern encompass a wide 
variety of food habits, ranging from frugivory and nectar-feeding (Samoan flying fox, red fruit bat, 
and Mexican long-tongued bat) to various styles of insect feeding in the remaining species. For the 
insectivorous species, dietary analyses have resulted in descriptions of insect prey classified by 
order or family for each, with some species more thoroughly investigated than others. Tendencies 
to focus on certain groups and sizes of prey vary with species, but dietary studies and feeding 
observations also have shown that some of the insectivorous species of concern are opportunistic 
in taking prey, and that prey types can vary among regions. 
Earlier studies focused on accurate qualitative descriptions of bat foraging made through care¬ 
ful naturalistic observations. These descriptions revealed a diversity of foraging styles among 
insectivorous species, ranging from those that feed close to and sometimes glean prey from the 
ground (California leaf-nosed bat) to those thought to forage at great heights on insects swept aloft 
by rising air currents (greater bonneted bat) or that forage mainly over the surfaces of permanent 
water (Yuma myotis). Species also differ in their proclivities to ‘hawk’ insects in the open air or to 
forage very close to vegetation. Naturalistic observations have been augmented over the past 20 
years by radio-tracking studies and use of acoustic sampling. In particular, tracking studies have 
resulted in more detailed observations pertinent to the sizes of foraging areas and distances trav¬ 
eled from roosts by foraging bats over the short lives of radio transmitters (one to two weeks), traits 
that also vary greatly among the few species studied. Distances from roosts traveled by foraging 
bats range from maxima of 43-50 kilometers for spotted bats to 1.8 kilometers for the eastern 
small-footed myotis. Foraging home range areas include estimates of 2.1 hectares for the red fruit 
bat, 38 hectares for the long-eared myotis, 10-100 hectares for the eastern small-footed myotis, two 
to 225 hectares for Rafmesque’s big-eared bat, 304-647 hectares for the long-legged myotis, two 
to eight square kilometers for the Samoan flying fox, an average of 297 square kilometers in spot¬ 
ted bats, and up to 474 square kilometers for Underwood’s bonneted bat. 
Roosting Habits. — Based on our reviews of roosting habits that appear in the species 
accounts, considerable amounts of information have been learned on multiple levels about roost 
use by “forest bats” that roost primarily in hollow trees in bottomland hardwoods (Rafmesque’s 
big-eared bat and southeastern myotis; about 60 papers) and to some extent in snags and under bark 
in various western forests (Allen’s big-eared bat, Arizona myotis, long-legged myotis, fringed 
myotis, long-eared myotis, Yuma myotis; about 140 papers). The increase in information about 
roosts of these species is tied directly to the interest in improving forest management practices to 
benefit bats. Perhaps somewhat unanticipated, in some areas western forest bats were often tracked 
to roosts in rock crevices rather than roosts in trees and snags (see corresponding species accounts 
for details). 
Less information has accrued about species that do not roost in trees and snags. Far fewer 
papers have appeared during the most recent decade on species known primarily to roost in rock 
crevices on cliff faces (spotted bats, greater bonneted bats, and big free-tailed bats; 18 papers). 
Increasing information has been accruing on the two species that roost in small crevices in rocks, 
soil, and under talus (eastern and western small-footed myotis; 46 papers). Three species that roost 
primarily in caves and abandoned mines varied greatly in numbers of recent papers: Townsend’s 
big-eared bats were the subject of 36 papers, cave myotis of 16 papers, and we found only a single 
