Echolocation calls of Myoti$ frater emitted during the search phase consist of brief frequency-modulated pulses. The sound signals are comprised of three harmonics of which the first one is of the highest intensity and occurs in all echolocation calls. The frequency of this fundamental harmonic ranges from 110.8 to 50.2kHz, and its duration is about 3.5ms. The second and the third harmonics are relatively weak, occurring in 50.0% and 25.0% of echolocation calls respectively, with frequencies ranging from 138.4 to 116.6 kHz for the second harmonic and from 193.6 to 170.8kHz for the third harmonic. We presume that, according to the echolocation call features, Myotis frater probably forages the insects on the ground of complex environments.