O’SHEA, CRYAN & BOGAN: UNITED STATES BAT SPECIES OF CONCERN 
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to rabies occur (for example, Constantine, 1979, 1988; Constantine et al., 1979), but the presence 
of rabies-virus-neutralizing antibodies in individuals sampled in Colorado (Bowen et al., 2013) 
suggests some degree of immune resistance to this virus. White-nose syndrome has not been 
reported for this species. Hamm et al. (2017) discovered actinobacteria (including Streptomyces ) 
with anti-fungal properties on wings of these bats and postulated that actinobacteria may have 
defensive properties against the fungus that causes white-nose syndrome as it moves into western 
North America. 
Excessive collecting no doubt had impacts on survival in local populations in the past (for 
example, Easterla, 1973). Maximum longevity has been reported as at least 18 years (Tuttle and 
Stevenson, 1982). 
Population Trend: Few data on population trends in this species are available. Ellison et al. 
(2003) analyzed counts at two summer colonies in Arizona but found no evidence of trends, where¬ 
as counts at one hibemaculum used by small numbers of fringed myotis decreased from 1969 to 
1992. 
Weller (2008) evaluated sampling design considerations for use of occupancy estimation mod¬ 
els to assess population status and habitat associations of this species in the Pacific Northwest. 
Occupancy was determined using captures in mist nets and echolocation recordings during four 
surveys at 51 carefully selected sites in Washington, Oregon, and northern California, and estimat¬ 
ed based on a series of habitat models (including categories for successional stage and conserva¬ 
tion reserve status) that were ranked using Akaike’s Information Criteria. Fringed myotis were 
detected at 21 sites (observed occupancy of 0.412). Model-averaged detection probability estimates 
were 0.252 ± 0.07 (SE), the second lowest of eight species sampled, and overall occupancy esti¬ 
mates were 0.605 ±0.16 (SE) using the best ranking model. Point estimates of occupancy were 
higher in late-succession/old growth habitat (Weller, 2008). Increased precision would have been 
possible with greater numbers of surveys per site and greater numbers of sites, or perhaps by 
increasing the numbers of identifiable echolocation calls recorded (Weller, 2008). 
Species dynamic distribution models were constructed using Bayesian hierarchical modeling 
techniques for 12 species of bats in Washington and Oregon based on an eight-year monitoring pro¬ 
gram; bat activity was sampled with mist nets and acoustic detectors, and the analysis accounted 
for detectability and annual turnover in bat occurrence (Rodhouse et al., 2015). This was the only 
species that showed a decline in occurrence probabilities with time and that was considered to be 
at risk (Rodhouse et al., 2015). 
Management Practices and Concerns. — In studies of several species of bats (including 
M. thysanodes ) roosting under loose bark or in lightning-caused cracks of snags in northern Ari¬ 
zona, Rabe et al. (1998a) recommended measures to help recruit 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). 
Analysis of roost-tree characteristics for fringed myotis in old growth Douglas fir forests of 
northwestern California showed they utilize tall snags in early stages of decay within stands with 
multiple similar roosts (see above); investigators recommended that forest management should 
retain the tallest dead or dying trees, and retain the oldest live trees within green-tree retention 
zones for future use as bat roosts (Weller and Zabel, 2001). 
In Colorado (where few roosts have been located), available data indicate that trees and snags 
are much less important for roosting than are rock outcrops and cliff faces (Hayes and Adams, 
2015). Therefore investigators recommend future identification and protection of roost sites and 
