O’SHEA, CRYAN & BOGAN: UNITED STATES BAT SPECIES OF CONCERN 
183 
to regularly replenish snags suitable as roosts following rotation harvests (for characteristics of 
snags used as roosts see above under “Roosting Habits”). The half-lives of snags used as roosts 
were found to typically be much shorter than those of snags that were not specifically known to be 
used as roosts (Lacki et al., 2012). 
Frequent roost switching and the relatively short lives of exfoliating bark roosts indicate that 
long-legged myotis and other species utilizing ponderosa pine snags with exfoliating bark may 
require more suitable snags than are needed by cavity-nesting forest birds (Rabe et al., 1998a; 
Baker and Lacki, 2006). Baker and Lacki (2006) suggested that snag retention for bat roosts should 
be large diameter (for example, greater than 60 centimeters diameter at breast height) and sur¬ 
rounded by snag densities of 40 snags or more per hectare in their ponderosa pine study areas in 
Oregon and Washington, and that both upslope (favored by lactating females) and riparian (favored 
by pregnant females) habitats include snags retained for bat roosting habitat. In studies of several 
species of bats (including long-legged myotis) roosting under loose bark or in lightning-caused 
cracks of snags in northern Arizona, Rabe et al. (1998a) recommended measures to help recruit 
ponderosa pine snags with loose bark as bat roosts. They suggested that forest management should 
retain large trees that die in place, thin stands of small trees to allow faster development of larger 
trees, and kill live large trees in areas of low snag density to hasten roost development. Prescribed 
fire but with protection of existing snags also may help promote development of future snags (Rabe 
et al., 1998a). Baker and Lacki (2006) agreed with these recommendations. 
Basal hollows of “legacy trees’ (large old trees that have been spared during harvest or other 
disturbances) are also used as roosts in redwood forests of northern California, where Mazurek and 
Zielinski (2004) recommended the management strategy of maintaining and recruiting such trees. 
Long-legged myotis will use artificial roosts constructed to mim ic exfoliating bark on snags in 
ponderosa pine forests in northern Arizona (Mering and Chambers, 2012). They have accepted 
installation of gates at the hibemaculum at Jewel Cave National Monument in South Dakota 
(Choate and Anderson, 1997), are reported to accept well-designed gates at abandoned mines in 
Colorado (Navo et al., 2000), and were captured entering gated mines in Idaho (Derusseau and 
Huntly, 2012). 
Myotis yumanensis — Yuma myotis (Family Vespertilionidae) 
Conservation Status. — National and International Designations: U.S. Fish and Wildlife 
Service (1994, 1996a,b): Species of Concern (inactive, former Category 2 candidate for listing 
under the U.S. Endangered Species Act). Bureau of Land Management (2011b, 2015b, 2017): Sen¬ 
sitive Species (California, Idaho, Nevada state offices). International Union for the Conservation 
of Nature (2017): Least Concern. NatureServe (2017): Species Rounded Global Ranking G5 - 
Secure; Subspecies M. y. oxalis Rounded Global Status T2, Imperiled. 
State Designations: Arizona Game and Fish Department (2012): Tier IB Species of Greatest 
Conservation Need. California Department of Fish and Wildlife (2017): Special Anim als List. 
Montana Fish, Wildlife and Parks (2015a): Potential Species of Concern. Texas Parks and Wildlife 
(2012): Species of Greatest Conservation Need. Utah Division of Wildlife Resources (2015; Sutter 
et al., 2005): Species of Greatest Conservation Need Tier III. Wyoming Game and Fish Department 
(2017a,b): Species of Greatest Conservation Need, Tier III. 
Description. — This is a small-to-medium sized myotis. Yuma myotis (Fig. 37) show clinal 
geographic variation in size, with larger specimens in the northeastern part of the distribution and 
smaller in the southwest (Harris, 1974). In some areas where ranges overlap, the Yuma myotis may 
be difficult to distinguish from little brown myotis (M. lucifugus; Parkinson, 1979; see below). 
Such areas include northern California and south-central Oregon, Washington, and southern British 
