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PROCEEDINGS OF THE CALIFORNIA ACADEMY OF SCIENCES 
Series 4, Volume 65, Supplement I 
Myotis thysanodes — Fringed 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). U.S. Forest Service (2005a,b): Sensitive Species 
(M thysanodes, M. thysanodes vespertinus). Bureau of Land Management (2009a,b, 2010a,b,c, 
2011b, 2015a,b): Sensitive Species (California, Colorado, Idaho, Montana, Nevada, North Dakota, 
Oregon, South Dakota, Utah, Wyoming state offices). International Union for the Conservation of 
Nature (2017): Least Concern. NatureServe (2017): Species Rounded Global Status G4, Appar¬ 
ently Secure; subspecies M. thysanodes pahasapensis and M. thysanodes vespertinus Rounded 
Global Status T2, Imperiled. 
State Designations: California Department of Fish and Wildlife (2015b, 2017): Special Ani¬ 
mals List, Species of Special Concern. Colorado Parks and Wildlife (2015b): Species of Greatest 
Conservation Need, Tier I. Idaho Department of Fish and Game (2005): Species of Greatest Con¬ 
servation Need (not included in Idaho Department of Fish and Game, 2015). Montana Fish, 
Wildlife, and Parks (2015a,b): Species of Concern, Species of Greatest Conservation Need S3. 
Nebraska Game and Parks Commission (2011): At-Risk Species Tier I (as M. t. pahasapensis ). 
Nevada Department of Wildlife (2013): Protected Mammal, Species of Conservation Priority. 
Nevada Department of Conservation and Natural Resources (2015a): S2 Imperiled. Oregon 
Department of Fish and Wildlife (2005,2008): Sensitive Species, Vulnerable. South Dakota Game, 
Fish, and Parks (2014): Species of Greatest Conservation Need (as M. t. pahasapensis ). Texas 
Parks and Wildlife (2012): Species of Greatest Conservation Need, Vulnerable. Utah Division of 
Wildlife Resources (2015; Sutter et al., 2005): Species of Greatest Conservation Need. Washing¬ 
ton Department of Fish and Wildlife (2015a): Species of Concern. Wyoming Game and Fish 
Department (2017a,b): Species of Greatest Conservation Need, Tier II. 
Description.— The 
fringed myotis (Fig. 31) is a 
medium to large sized myotis 
with large ears that extend about 
three to five millimeters beyond 
the snout when laid forward 
(Miller, 1897). Forearm lengths 
range 39^47 millimeters, and ear 
lengths 12-22 millimeters (for 
example, Barbour and Davis, 
1969; O’Farrell and Studier, 
1980; Hoffmeister, 1986). Body 
mass ranges six to nine grams 
(Armstrong et al., 2011; Ammer- 
man et al., 2012a), with individu¬ 
als recorded as high as 11.7 g 
during autumn fat deposition 
(Ewing et al., 1970). The short, dense fringe of hair on the distal edge of the uropatagium is dis¬ 
tinctive, but a much less pronounced fringe can sometimes be discerned on the trailing edge of the 
tail membrane of the long-eared myotis (sometimes best seen with magnification). The long-eared 
myotis also is smaller than the fringed myotis and has longer and darker (blackish) ears. The two 
species are reported to be difficult to distinguish in hand in western South Dakota and eastern 
Wyoming (see personal communications in Dewey, 2006). 
Figure 31. Fringed myotis, Myotis thysanodes (photo by J. Scott Alten- 
bach). 
