Social calls of the Serotine bat (Eptesicus serotinus)
Recordings from 2015 to 2025
These agonistic calls, type B social calls, were emitted by a serotine bat that was being chased by a Nathusius' pipistrelle.
Viideo footage from: Sarah Mahie
More interspecies interaction between a serotine bat and a Nathusius' pipistrelle like the previous recording was witnessed on a different occasion. About five minutes after a Nathusius' pipistrelle was emitting type D social calls (914884 and 914885), a serotine bat flew by emitting multiple agonistic calls. The Nathusius' pipistrelles had their roost nearby, so possibly another chase was happening during the time of this recording.
Date of recording: 2024-06-19 Recorded by: Olivier van Aken Audio file: 914886
Many social calls of serotine bats that are recorded from within a maternity roost are not particulary distinguishable from those produced by other species in similar settings. However, some call types both look and sound quite distinctive (Middleton et al., 2022). The following recordings of calls emitted from within a maternity roost of at least 30 individuals are examples of those distinctive calls (type A, B and type C):
Video footage from: Sander Boersma, Boaz van Die, Sarah Mahie
Video footage from: Sander Boersma, Boaz van die, Sarah Mahie
This species is not often encountered producing social calls while in flight away from the roost (Middleton et al., 2022). The following type C social calls have an upside-down U-shape, with the exception of the social call in the middle that is mainly dropping down in frequency. The latter call is very similar to the serotine bat social call recorded by U. Marckmann, figure 8.7.1 in the book Social Calls of the Bats of Britain and Ireland (Middleton et al., 2022).
Date of recording: 2024-07-24 Recorded by: Charlotte Serrarens Audio file: 923069
During one of our surveys, there was an encounter with two foraging serotine bats. They were flying back and forth through the street when one of the serotine bats suddenly emitted a series of type C high frequency FM-calls.
Date of recording: 2024-06-03 Recorded by: Hannah Floor Audio file: 911601
There is not much known about the mating behavior of serotine bat. The upper snippit of the image below contains calls of a stationary serotine bat. Serotine bats emitting calls stationary have been witnessed a few times over the years and it is presumed that these repetitive calls have a function as advertisement calls. The lower snippit contains social calls of serotine bat. These social calls were emitted shortly after the stationary serotine bat flew away from it's perching spot, most likely due to a second serotine bat appearing in the area and joining the event.
Date of recordings: 2015-08-29 Recorded by: Erik Korsten Source image: Zoogdiervereniging: Bureau Waardenburg - Voortplanting bij de laatvlieger Audio: Soundcloud
The social calls in the following recording are similar to the recordings made on made on 2025-05-14 (later on this page) and the seocial calls in the second snippit are also similar to the social calls recorded by Erik Korsten (second snippit of the previous example).
Date of recording: 2024-08-26 Recorded by: Fabienne Schwab Audio file: 936309
A new year has begun and the new season starts with field visits focussed on the swarming behavior of serotine bats, since they appear to swarm and emit stationary calls during spring as well. It was quite succesful, since the following series of social calls were recorded. These social calls are very similar to those recorded by Erik Korsten (2028). Directly after the social calls, more regular looking echolocation of at least two serotine bats become visible in the recording.
Date of recording: 2025-05-14 Recorded by: Sarah Mahie Audio file: 998717
About 10 minutes later, 230 meters southeast as the crow flies, two serotine bats were seen swarming. A few type C social calls were recorded together with wiggly echolocation calls. A few days prior, I was present at a "difficult bat sounds" workshop and we discussed the wiggly echolocation calls of serotine bats. Multiple people have recorded these calls and they always seem to occur when at least two serotine bats are present. Perhaps they have a social function.
I must admit that the following social calls were also hard to identify at first, but the social calls in the recordings share a lot of similarities with the previous mentioned recordings. However, the lower frequency type C social calls were new to me. I learned that serotine bat can produce those too. They appear to be very similar to the calls recorded by M. van der Sijpe, figure 8.7.4 in the book Social Calls of the Bats of Britain and Ireland (Middleton et al., 2022)
Some hooked echolocation calls were also recorded! During the recording of May, the serotine bats were returning to their maternity roost.
Date of recordings: 2025-05-23 Location: Ede, Gelderland, The Netherlands
Date of recordings: 2025-04-28
Location: Ede, Gelderland, The Netherlands
Audio file: 1001695
These social calls were recorded during the same evening as the hooked echolocation calls of April:
Date of recordings: 2025-04-28 Recorded by: Sjoerdtje de Boer File: 1001697
These social calls were recorded the evening after the hooked echolocation calls of May, inbetween serotine bats leaving the roost:
At least three individual serotine bats are present in the following recording. It contains serotine bat buzzing followed by type C social calls:
Date of recording: 2025-05-19 Audio file: 1046016
These low-frequency type C social calls were recorded in the same street as the previous recording, about a month later:
Date of recording: 2025-06-11 Audio file: 1046018
The following recording contains multiple kinds of social calls. At least two individuals are present. There are some type C social calls that go lower in frequency, type C social calls that are higher in frequency and something that almost appears as a very creative feeding buzz. Very wiggly echolocation calls are present as well. The first recording was made at 23:56. In the same area, about 750 meters away as the crow flies, more serotine bat social calls were recorded a little later at 00:19 (so about 23 minutes later). Spoiler: a maternity roost was found at the exact location of the latter recording during an early morning survey.
The first recording:
Second recording:
(The following snippits are altered to edit the noise out. I was, sadly, cycling on a squeaking bicycle during the event.)
These social calls were recorded while serotine bats were swarming before entering their roost in the morning. This roost was found by deliberately waiting at the location where social calls were recorded the previous survey a month prior (2025-06-17, earlier on this page). I saw at least four serotine bats swarming and tapping a roost entrance. Social calls were emitted before and after entering the roost. The following evening, 27 individual serotine bats were counted leaving the roost.
Type B social calls emitted while in flight. Two serotine bats were seen, one chasing the other. A summer roost was found nearby later that morning.
And more serotine bat social calls were recorded with two serotine bats present (the echolocation of the second bat joins after these social calls).
Date of recording: 2025-07-03 Recorded by: Sarah Mahie, Boaz van Die Audio file: 1011134
Some more buzzing(?) followed by a very nice looking type C social call:
Some very nice and prominent type C social calls, recorded just two minutes after the previous recording of Boaz at a location 3 km away as the crow flies:
Date of recording: 2025-07-12 Recorded by: Sarah Mahie Audio file: 1015569
These social calls were recorded while serotine bats were swarming before entering their roost in the morning:
Date of recordings: 2025-07-13 Recorded by: Sarah Mahie, Boaz van Die Audio files: 1016878, 1016870, 1016861, 1016882, 1016862, 1016864, 1016865, 1016867, 1016871, 1016873, 1016875, 1016876, 1016877, 1016879, 1016881, 1016883, 1016884, 1016885, 1016888, 1016894, 1016896, 1016901 (Echo Meter), 1016886, 1016887, 1016890, 1016891, 1016892, 1016895 (Batlogger)
Possibly some more buzzing, recorded with the microphone outside of a slow driving car:
Date of recording: 2025-07-19 Recorded by: Sarah Mahie, Boaz van Die Audio file: 1017414
In autumn, more buzzing accompanied by type C social calls were recorded.
Date of recording: 2025-08-28 Recorded by: Sarah Mahie Audio file: 1033511
All recordings are licensed under the following Creative Commons Attribution-NonCommercial-NoDerivs 4.0 license and in courtesy of Sarah Mahie.
All the original video footage can be found on our Youtube channel: United by Ecology
All sonograms are screenshots of the recordings imported in the ultrasound analysis software BatExplorer 2.2 (Elekon, Switzerland).
Bibliography:
- Erik Korsten (2018). Voortplanting bij laatvliegers. Expertise-meeting Laatvlieger. Bureau Waardenburg.
- Jon Russ (2021). Bat Calls of Britain and Europe: a Guide to Species Identification. Pelagic Publishing.
- Neil Middleton, Andrew Froud and Keith French (2022). Social Calls of the Bats of Britain and Ireland (second edition). Pelagic Publishing.
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