216 
PROCEEDINGS OF THE CALIFORNIA ACADEMY OF SCIENCES 
Series 4, Volume 65, Supplement I 
big free-tailed bats rely on earthen ponds constructed for livestock as sources of water in some 
regions, and maintenance of earthen ponds during times of drought has been recommended. Main¬ 
tenance of larger-sized ponds may be especially critical for big free-tailed bats and greater bonnet¬ 
ed bats. Mining and quarrying at cliffs, road construction through cliff-walled canyons, disturbance 
from recreational climbing, and submergence by large water impoundments have been noted as 
having potential impacts on colonies of these cliff-dwelling bats. 
Roost use and roosting habitat have been topics of much study in bats of western coniferous 
forests and woodlands. Several general recommendations for forest management in dry ponderosa 
pine forests include retaining in place patches of large trees that die, thinning of stands of small 
trees to allow faster development of larger trees, killing of live large trees in areas of low snag den¬ 
sity to hasten roost development, and removing ground fuels from areas surrounding large snags 
prior to using prescribed fire. In some areas, using artificial roosts constructed to mimic exfoliat¬ 
ing bark on snags may serve as surrogate roosts while management for developing large snags pro¬ 
ceeds. 
Recommendations for management in more moist forests such as those of the Pacific North¬ 
west also include maintaining large-diameter conifer snags in early to intermediate stages of decay. 
Snags that are exposed to moderate to high levels of solar radiation (snags that protrude above the 
canopy, have low canopy closure, or are located in gaps or near stand edges) are most important, 
especially when retained in clusters, and particularly where they are in upland habitats near water. 
Retention of large green trees and snag creation is recommended, as is maintaining remnant patch¬ 
es of structurally diverse and typically older forest stands with large snags. Thinning of dense 
stands to accelerate development of large-diameter trees for future roosts, and creation of gaps to 
increase solar radiation were also recommended, as was retention of trees with large basal hollows 
in redwood forests. Although the full scope of hibernation sites used by western forest bats are not 
yet fully known, caves and mines have been documented as overwintering sites for these species. 
Utilization of bat-compatible closure methods to prevent disturbance at caves and mines during this 
critical time of year has been recommended and undertaken in several areas. 
Recommendations for management of the two species generally associated with western ripar¬ 
ian areas nested within a wider variety of broader habitats (Arizona myotis and Yuma myotis) have 
mostly centered on maintaining roosting habitats for maternity colonies. General recommendations 
made for management for roosts in trees and snags in western forest types apply where these 
species are found in such habitats. Minimization of disturbance around known roosting sites is 
important, including bat-compatible restrictions to access by people at caves and abandoned mines 
used by Yuma myotis. Arizona myotis appear to forage in experimentally restored cottonwood-wil- 
low riparian habitats along the lower Colorado River. 
The remaining three species of concern include two species that primarily roost in caves and 
abandoned mines (Townsend’s big-eared bat and cave myotis), and one that roosts in caves and 
mines but is also found roosting in snags in forests and in high cliffs (Allen’s big-eared bat). Most 
management recommendations for cave myotis and Townsend’s big-eared bats have focused on 
roost protection. Cave myotis are reported to be very sensitive to disturbance. In several studies 
colonies of cave myotis have responded well to seasonal closure of roosts and installation of bat- 
compatible gates, although in some areas these methods may not work well with very large 
colonies. Townsend’s big-eared bats are also very sensitive to disturbance both in winter hibemac- 
ula and summer maternity colony sites. Restrictions to human visitation in these sites are impor¬ 
tant to avoid unintentional disturbance as well as vandalism and killing. Destruction or sealing of 
abandoned mines for human safety will remove roosting habitat completely, and surface mining 
will destroy foraging habitat. Management plans are available with details for methods to close 
