EN
We measured the shape of pinnae from fluid-preserved, museum specimens of 33 Myotis californicus and 39 M. ciliolabrum and cranial characters from 40 skulls of each species. We also measured 40 specimens of Eptesicus fuscus, which were used as an outgroup. Significant differences were found in aural shape and tragus height between the two species of Myotis. Archived echolocation calls from the two species from across the range segregated, further suggesting that morphological and call characters are intercorrelated. We tested this relationship using 17 M. californicus and 12 M. ciliolabrum captured in the field for external measurements and echolocation call recordings (n = 1,124 calls in 52 call files, x = 2.3 call files per released bat), and found significant differences (most P < 0.001) in pinnae and call morphology between M. ciliolabrum and M. californicus similar to those observed in ‘museum’ samples. We found that small interspecific differences in pinna shape and size are correlated with differences in the frequency ranges (larger pinna, lower frequency).