Lutra 54(1)_Van De Sijpe_2011

Differentiating the echolocation calls of Daubenton’s bats, pond bats and long-fingered bats in natural flight conditions

Echolocation calls of the three European species of trawling bats were studied in their natural habitats, during hunting, commuting and swarming activities. Daubenton’s bats (Myotis daubentonii) used pulse durations below 8 ms in most cases, however on rare occasions they used some longer search phase calls up to 13 ms. Pond bats (Myotis dasycneme) used a wide variety of pulse durations of up to 26 ms, with signals of >15 ms regularly recorded. The longest pulse durations recorded from the long-fingered (Myotis capaccinii) bat were 8 ms. The three species usually emitted starting frequencies below 100 kHz, however some recordings made at very close range revealed starting frequencies up to circa 120 kHz in Daubenton’s bat and the long-fingered bat and circa 110 kHz in the pond bat. Although the peak frequencies were variable in all species, the pond bat generally used lower peak frequencies (median 41 kHz for durations of 1-4 ms and median 35 kHz for durations of >14 ms) compared to Daubenton’s bat (median 49 kHz for durations of 1-4 ms and median 37 kHz for durations of 8-14 ms) and the long-fingered bat (median 45 kHz for durations of 1-4 kHz). End frequencies were significantly higher in the long-fingered bat (median 32 kHz, for durations of 1-4 ms) than in the other two species (pond bat median 25 kHz, Daubenton’s bat median 26 kHz, for durations of 1-4 ms). Quasi-constant frequency parts in the middle of the signal were only found in the pond bat. Long-fingered bats sometimes used pulse series with alternating end frequencies.