Echolocation calls of Myotis frater (Chiroptera : Hipposideridae) during search flight

Echolocation calls of Myotis frater emitted during the search phase consist of brief frequency-modulated pulses. The sound signals are comprised of th ree harmonics of which the first one is of the highest intensity and occurs in all echolocation calls. The frequency of this fundamental harmonic rang es from 110.8 to 50.2 kHz, and its duration is about 3.5 ms. The second and the third harmonics are relatively weak, occurring in 50.0% and 25.0% of e cholocation calls respectively, with frequencies ranging from 138.4 to 116. 6 kHz for the second harmonic and from 193.6 to 170.8 kHz for the third har monic. We presume that, according to the echolocation call features, Myotis frater probably forages the insects on the ground of complex environments.