Durham Bat Group: Bat Calls

The kind of sound made by a bat can help in identifying the species you are observing.

 

Common name Repetition
rate
Rhythm Tone Duration FM/CF Peak
power
Barbastelle 15 Regular wood blocks 4ms 45>32;35>28 32kHz
Serotine 9 very irregular hand clap to "chink" 5 ms 55>25 28 kHz
Bechstein's 10 irregular sharp tick 2.5 ms 110>34 50 kHz
Brandt's 12 regular dull click 5 ms 65>41 45 kHz
Daubenton's 14 regular flat click 6 ms 62>39 50 KHz
Whiskered 12 regular dull click 5 ms 65>41 45kHz
Natterer's 30 very irregular crumpled
cellophane
2 ms 70>31 38 kHz
Liesler's 5 irregular chip-chip..chop 11 ms 31>25 28 kHz
Noctule 3 irregular chip-chop 14 ms 20>18 19 kHz
Nathusius' pip 10 quite regular chink 8 ms 49>39 HS 39 kHz
Common pip 11 quite regular chink 6 ms 55>45 HS 48 kHz
Soprano pip 12 quite regular chink 6 ms 65>54 HS 56 kHz
Brown
long-eared
10 regular quiet clicks 2 ms 62>34 40 kHz
Grey
long-eared
10 regular quiet clicks 2 ms 63>30 48kHz
Greater
horseshoe
12 continuous warbles 50 ms 69 kHz 69 kHz
Lesser
horseshoe
12 continuous warbles 40 ms 99kHz 99 kHz

 

The table above is a rough guide only, as the characteristics of a bat call are strongly affected by its environment.

A bat flying in the open doesn't need to repeat so quickly, and can use a longer duration call.  Calls with a duration less than about 4ms are too short to have a clear pitch and are heard instead as some kind of click; so Pips, Lieslers and Noctules have a clear pitch to their call while Natterers,  Daubentons, Whiskered/Brandts and Long-eared are generally click-like with only occasional calls being long enough to have a clear pitch.
Its important to realise that the quality of a click sound will be impaired if your bat detector speaker is small (as for example some of the Ciel detectors) because the clicks have frequency components below 200Hz; so if you want to identify the bats its best to use headphones.
In the FM/CF column: 65>40 indicates a sweep from 65 down to 40 kHz; HS hockeystick; otherwise constant frequency.

Bristol's "Bats of Britain" has lots of information - including spectrograms and time expansion recordings of all the british bats (calls courtesy of Dr. Stuart Parsons).