The Yuma Myotis is a medium-size Myotis. Its dorsal fur varies from pale brown to nearly black; the fur on its underside is paler. The wing membranes and ears are dark brown. The ears reach the nostrils when pushed forward; the tragus is blunt and about half the length of the ear. The calcar is not keeled. The typical Myotis skull has a steeply sloped forehead.
IdentificationThe ear and tragus of the Yuma Myotis are smaller than that of the Fringed Myotis (Myotis thysanodes), Northern Long-eared Myotis (Myotis septentrionalis), Western Long-eared Myotis (Myotis evotis) and Keen's Long-eared Myotis (Myotis keenii). The absence of a keel on the calcar distinguishes the Yuma Myotis from the Long-legged Myotis (Myotis volans), California Myotis (Myotis californicus) and Western Small-footed Myotis (Myotis ciliolabrum). This species is most similar in external appearance to the Little Brown Myotis (Myotis lucifugus) - in some regions it can be extremely difficult to discriminate between the two. For diagnostic external and cranial criteria that identify these two bats see the account for the Little Brown Myotis.
Dental Formulaincisors: 2/3
Measurementstotal length: 82 (60-99) n = 322
tail vertebrae: 36 (27-45) n = 324
hind foot: 9 (6-13) n = 323
ear: 14 (8-16) n = 202
tragus: 7 (5-10) n = 212
forearm: 34.3 (30.0-38.0) n = 273
wingspan: 238 (205-260) n = 208
weight: 6.6 (4.0-8.5) n = 153