Bat sounds and sound diagnostics of bat species occurring in Aukštadvaris area

8th European Bat Detector WorkshopAukštadvaris, 18—21 August 2011

Matti Masing

Contents

Bat species living in northern Europe

Detector-based identification of bats in flight

Equipment to study bat sounds

Identifying bats in the field (on spot)

Analysis of recorded bat sounds, using sound analysis software

Sonogram, power spectrum, oscillogram

Measuring bat sounds

Listening to bat sounds from recorded samples

Bat species living in northern Europe (15)

Table 1. European boreal bats (15 species)

Species name in Latin Species name in English Relative abundance in southern Lithuania-----------------------------------------------------------------------------------------------------------------------Myotis dasycneme Pond Bat **Myotis daubentonii Daubenton's Bat ****Myotis brandtii Brandt's Bat ** Myotis mystacinus Whiskered Bat *?Myotis nattereri Natterer's Bat *

Plecotus auritus Brown Long-eared Bat ***Barbastella barbastellus Barbastelle **

Pipistrellus nathusii [m] Nathusius's Pipistrelle (2 sonic forms) ****Pipistrellus pipistrellus[m] Common Pipistrelle **Pipistrellus pygmaeus [m] Soprano Pipistrelle **

Eptesicus serotinus Serotine ***Eptesicus nilssonii Northern Bat **

Vespertilio murinus [m] Parti-coloured Bat *?

Nyctalus noctula [m] Noctule ***Nyctalus leisleri [m] Leisler's Bat *?

[m] most individuals probably migrate (they occur in Lithuania from April till October)

Detector-based identification of bats in flight

Detector-based identification of bats in flight, 1

Bats can be identified on the basis of their sound emitted during flight (Ahlén, 1981; Ahlén & Baagøe,1999).

In European boreal region, north of 55 n.l., 15 bat species occur in a relatively large area (Table 1).

Those are the species we expect to find here during 8th European Bat Detector Workshop in Aukštadvaris Regional Park, Lithuania in August 2011.

Most of them were already found in this area during some nights of extensive detector-based research carried out in August 2005 (Masing & Baranauskas, 2011).

Detector-based identification of bats in flight, 2

Detector-based identification is one possibility to identify the flying bats. It is probably the best possibility, and a most convenient one for a student of bats, especially during dark late-summer nights when there is not much to see ...

So, what are the basic sound characters to identify boreal bats in flight?

Sound characters depend on the detector, so let us have a look at some of them first.

Equipment to study bat sounds – detectors

Pettersson D240x (on the right) has two systems, heterodyne (HET) and time-expansion (TEX). Both produce audible sound, which can be used to identify bats on spot. TEX sound, in addition, can be stored, either in a recorder or a PC, and later analysed in detail for species identification.

Pettersson D200 (on the left) has only heterodyne system, which makes it less valuable for species identification on spot.

Equipment to study bat sounds – recorders

(Panasonic RQ-L11, Olympus VN-5500PC, TrekStor i-Beat Nova 4GB)

Equipment to study bat sounds – a computer

Equipment to study bat sounds – sound analysis software opened in a computer

Identifying bats in the field (on spot)

Identifying bats in the field (on spot)

In Pettersson D240x there are two systems both of which can be used to identify bats in the field. One is the heterodyne system and the other is the time-expansion system (Pettersson Elektronik, 2011).

The heterodyne system (HET), 1

It is very sensitive to ultrasound, if the microphone is good enough.

Narrowband species (Eptesicus, Nyctalus, Pipistrellus, Vespertilio) can be recognized on spot, using the best listening frequency (BLF) of their pulses. By changing frequency on the detector's display, an observer can easily find BLF if it is there. The bigger the animal, the lower the BLF, and vice versa.

NARROWBAND BATS (Eptesicus, Nyctalus, Pipistrellus, Vespertilio)

European boreal narrowband bats flying in a relatively open flight place, and relatively high from the ground or water surface, have usually BLF-s within the following ranges:

20 kHz (18-25) – Nyctalus noctula25 kHz (22-28) – Nyctalus leisleri

25 kHz (24-30) – Vespertilio murinus

27 kHz (25-30) – Eptesicus serotinus30 kHz (28-33) – Eptesicus nilssonii

40 kHz (35-41) – Pipistrellus nathusii s.str.43 kHz (40-46) – Pipistrellus livonicus (the high-calling sonic form of P. nathusii s.l.)46 kHz (43-52) – Pipistrellus pipistrellus55 kHz (50-64) – Pipistrellus pygmaeus

The heterodyne system (HET), 2

In good conditions of observation, all these 8 or 9 species (9 sonic forms) can be identified on species level on spot.

However, quite often problems appear.

First, „25 kHz bats“

Four species of European boreal bats (Eptesicus serotinus, Vespertilio murinus, Nyctalus noctula and N. leisleri) can produce strong smacking sounds with BLF around 25 kHz. The more south the observer goes for bats, the higher is the probability to encounter several species emitting this sound. In Finland it should be relatively easy, in Estonia it is harder. But in Lithuania it can be very hard!

Second, „43 kHz bats“

It is particularly hard to separate between P. nathusii and P. pipistrellus, if the first species appears to be the high-calling sonic form (livonicus). Then, overlapping BLF can occur between 42 and 46 kHz, which means that a pulse with BLF either below 42 kHz or over 46 kHz is required to correctly identify the flying bat (Masing, 2006).

Unfortunately, such is the situation in vast areas of eastern Europe during spring and summer.

The heterodyne system (HET), 3

BROADBAND BATS (Myotis, Plecotus)

All species of Myotis and Plecotus belong to this group. Except Myotis dasycneme, sometimes emitting pulses with BLF on 35 kHz (in a certain flight situation in an open space), none of them makes clear soft sound recognizable as BLF.

Time-expansion of the recorded sounds sometimes helps to identify into which narrowband species the animal belongs (e.g. Myotis dasycneme, Myotis daubentonii, Myotis brandtii/mystacinus, Myotis nattereri or Plecotus sp.).

In Lithuania we have at least 5 species of Myotis and at least one of Plecotus. Long-time learning and substantial field experience is required to identify those bats using only sound.

Sound characters to identify bats when using a heterodyne detector (summary)

In a relatively open flight place the following sounds can be heard from a heterodyne detector.

Sound rhythm is fast (interpulse intervals short, often 50-100 ms; human ear usually cannot separate the pulses) – Myotis sp., Plecotus sp., Barbastella sp., Pipistrellus sp.

Sound rhythm is relatively slow (interpulse intervals relatively long, often at least 150-200 ms; human ear usually can separate the pulses) – Eptesicus sp., Vestpertilio murinus; sometimes also Myotis dasycneme and Plecotus sp.

Pulses are very weak (when the bat is near, 1-10 m away) – Plecotus sp., Myotis nattereri.

Pulses are relatively strong (when the bat is near) – all other species.

Sound colour is rough (not soft) on any frequency („best listening frequency“ is missing) – broadband species (Myotis sp., Plecotus sp.).

Sound colour is relatively soft on a certain frequency („best listening frequency“, BLF) – narrowband species (Pipistrellus sp., Eptesicus sp., Vespertilio murinus, Nyctalus sp., Barbastella sp.; sometimes also Myotis dasycneme and Plecotus sp.

BLF shows to what species the bat belongs (BLF-s between 18 and 60 kHz; the bigger the animal, the lower is its BLF) –

see “The heterodyne system (HET), 1”.

So let us start listening to bat sounds!

((((((((((((((((( ........

........ )))))))))))))))))

Examples of bat sounds heard from heterodyne system, 1

NARROWBAND SPECIES (Eptesicus, Nyctalus, Pipistrellus, Vespertilio)

wav21 het20 noc lagendik - 30sek.wavwav22 het25 mur toit tanava kohal 10m - 24sek.wavwav23 het25 mur korgel joe kohal - 15sek.wavwav25 het27 ser-noc lagendik - 32sek.wav

wav26 het30 nil lagendik 15m - 31sek.wavwav28 het30 nil latvade vahel 20m - 44sek.wav

wav35 het40 nath lagendik 10m - 30sek.wavwav39 het55 pyg parvlem VP – 37sek.wavwav40 het35 nil-33s das-19s vallikraav - 57sek.wav

wav41 het14 mur territ - 08sek.wavwav42 het20 nath territ metsatee 5m - 11sek.wav

wav43 het15 nil VP dist 5m - 17sek.wavwav44 het20 nath VP dist 15m - 16sek.wav

Examples of bat sounds heard from heterodyne system, 2

BROADBAND SPECIES (Myotis, Plecotus)

wav30 het35 das vallikraav dist 20m - 43sek.wavwav31 het35 dau jogi dist 10-20m - 47sek.wavwav32 het35 bm 4m dist 2-5m - 33sek.wavwav33 hetx nat 5x dist 1-2m Leivits - 12sek.wavwav34 het35 aur parvlem VP d 5m kahin-krabin – 47sek.wav

The time-expansion system (TEX)

TEX is a good supplemantary method to identify boreal bats on spot. With TEX it should be relatively easy to recognize e.g. Barbastella barbastellus and Plecotus sp.; sometimes also Myotis dasycneme and Myotis nattereri. Slightly elongated, even pulses of Myotis daubentonii also sound species specific on TEX.

Examples of bat sounds heard from time-expansion system

SELECTED SPECIES from genera Eptesicus, Nyctalus, Pipistrellus and Vespertilio

wav04-pargi-nahkhiir-sonar.wavwav05-pargi-nahkhiir-vihtlemine.wavwav09-hobe-nahkhiir.wavwav10-hobe-nahkhiir-ketramine.wavwav18-kaabus-nahkhiir_hobe-nahkhiir.wavwav19-suurvidevlane_veelendlane.wav

SELECTED SPECIES from genera Myotis, Plecotus and Barbastella

wav02-suurkorv2.wavwav03-euroopa-laikorv.wavwav13-veelendlane.wavwav14-tiigilendlane-avavesi.wavwav15-tiigilendlane-maa.wavwav16-tommulendlane-habelendlane.wavwav17-Nattereri-lendlane.wavwav20-tiigilendlane-toit.wav

Analysis of recorded bat sounds, using sound analysis software

If field identification of a bat in flight fails, then the analysis of its preserved ultrasound can sometimes help.

Certain characters of pulses, and pulse intervals, can be used to characterize the bat, as well as to find species specific (diagnostic) sound characters.

Computer-based figures are used in sound analysis. Within BatSound programme the main figures to study are spectrogram (sonogram), oscillogram and power spectrum (energogram).

Sonogram, power spectrum (energogram)

Pulse shape is visible on sonogram, while peak frequency is measured from enegrogram (shown on the right upper corner of the figure).

Sonogram, oscillogram, energogram

Which sound character to measure from where?

Measuring bat sounds

Detector-based identification of bats in flight (summary)

Bats can be identified on the basis of their sound emitted during flight.

Several species (especially narrowband ones) can be identified on spot, using the heterodyne system of an ultrasound detector.

Additional species can be identified on spot if time-expansion system is used, and/or if visual characters of the bat in flight are observed.

Bat sounds from Aukštadvaris area, August 2005

Listening to bat sounds from recorded samples, 1

Sounds from Aukštadvaris area 2005, identified on species level – learn them well!

Species 1: aur25 Aukshtad-0806-k7 Streva jv kallas.wavSpecies 2: bar30-32 Aukshtad-0806-k8 jv kallas nolv.wavSpecies 2: bar32-33 Aukshtad-0805-k5-mets2-p5 0255 hea!.wavSpecies 3: bm45-46 Aukshtad-0806-k8 jv kallas sillake.wavSpecies 4: dau41-44 noc23-24 Aukshtad-0806-k1 baasi all jv kallas.wav

Species 5a: liv41-43 Aukshtad-0806-k9 jv kallas baasi taga hea!.wavSpecies 5b: nath39-42 pyg51-53 Aukshtad-0806-k3 kanjoni kesk sillake.wavSpecies 6: nil28-30 Aukshtad-0806-k3 kanjoni keskel sillake.wav

Species 7: noc21-22 Aukshtad-0806-k9 jv kallas baasi taga.wavSpecies 7: noc23-24 dau41-44 Aukshtad-0806-k1 baasi all jv kallas.wav

Species 8: pip45-46 Aukshtad-0806-k8 jv kallas sillake.wavSpecies 9: pyg51-53 noc21 Aukshtad-0806-k3 kanjoni kesk sillake.wavSpecies 9: pyg52-55 Aukshtad-0806-k5 jv E-kallas.wav

Species 10: ser25-27 Aukshtad-0805-aknast 0122 hea!.wav

Listening to bat sounds from recorded samples, 2

Sounds from Aukštadvaris area 2005, not identified thus far – can you help?

aurx-serx26-27 Aukshtad-0805-k1-p13 0024.wavdaux42-45 Aukshtad-0805-k1-p2 2236 oja kallas.wav

leix-serx25-26 Aukshtad-0806-k1 2317.wavliv42-43 soc-4imp Aukshtad-0806-k8 jv kallas sillake.wav

murx24-25 Aukshtad-0806-k1 2329 baasi all jv kallas.wavmurx25-29 Aukshtad-0806-k1 2326 baasi all jv kallas.wav

pipx43-47 Aukshtad-0805-k6 0414.wav

serx24-26 Aukshtad-0806-k1 2302.wavserx25-28 Aukshtad-0806-k1 2304 baasi all jv kallas.wavserx27-28 nath35-37 Aukshtad-0805-k6 0409 sild 2jv.wav

sp22-25 Aukshtad-0806-k1 2322 baasi all jv kallas.wavsp24-26 Aukshtad-0806-k1 2329 baasi all jv kallas.wav

References

Ahlén, I. 1981. Field identification of bats and survey methods based on sounds. – Myotis, 18—19, 128—136.

Ahlén, I. & Baagøe, H. 1999. Use of ultrasound detectors for bat studies in Europe – experiences from field identification, surveys and monitoring. – Acta Chiropterologica, 1, 137—150.

Masing, M. 2006. Perekonna Pipistrellus hääldiagnostika Põhja-Euroopas ja pügmee-nahkhiire (Pipistrellus pygmaeus Leach) leiud Eestis. – Eesti Looduseuurijate Seltsi aastaraamat, 84, 185—206. [Sound diagnostics in the genus Pipistrellus (Chiroptera, Vespertilionidae) in northern Europe and the finds of Pipistrellus pygmaeus in Estonia.]

Masing, M. & Baranauskas, K. (oral presentation) 2011. A detector-based bat survey in Aukštadvaris area (Lithuania) in August 2005. 8th European Bat Detector Workshop. Aukštadvaris, Lithuania 18—21 August 2011. 29 pp. (Masing Baranauskas 2011-08-18pr Aukstadvaris 2005.pdf)

Pettersson Elektronik. 2011. D240X Ultrasound Detector. [http://www.batsound.com/?p=9]

End of presentation

Thank you!

Aukštadvaris, 19 August 2011

Matti Masing