Analysis of Bat Call Recordings and Criteria for the Evaluation of Acoustic Identification of Species

Part 1 – Genera Nyctalus, Eptesicus, Vespertilio, Pipistrellus (nyctaloid and pipistrelloid Species), Barbastelle, Long-eared Bats and Horseshoe Bats in Bavaria

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Bayerisches Landesamt für Umwelt 2020 1 Bat protection in Bavaria

Analysis of Bat Call Recordings and Criteria for the Evaluation of Acoustic Identification of Species

Part 1 – Genera Nyctalus, Eptesicus, Vespertilio, Pipistrellus (nyctaloid and pipistrelloid Species), Barbastelle, Long-eared Bats and Horseshoe Bats in Bavaria

Translation: David Lee

Impressum

Bestimmung von Fledermausrufaufnahmen und Kriterien für die Wertung von akustischen Artnachweisen Teil 1 – Gattungen Nyctalus, Eptesicus, Vespertilio, Pipistrellus (nyctaloide und pipistrelloide Arten), Mopsfledermaus, Langohr- fledermäuse und Hufeisennasen Bayerns

Herausgeber: Bayerisches Landesamt für Umwelt (LfU) Bürgermeister-Ulrich-Straße 160 86179 Augsburg Tel.: 0821 9071-0 E-Mail: [email protected] Internet: www.lfu.bayern.de/

Konzept/Text: Ulrich Marckmann NycNoc GmbH, Himmelreichstr. 8, D-96052 Bamberg Burkard Pfeiffer Koordinationsstelle für Fledermausschutz in Nordbayern, Institut für Tierphysiologie, Universität Erlangen-Nürnberg, Staudtstraße 5, D-91058 Erlangen

Redaktion: Bernd-Ulrich Rudolph, LfU, Referat 55

Titelbild Sonagramm eines Sozialrufes (Trillers) der Rauhautfledermaus und von Ortungsrufen einer hoch rufenden Zwergfledermaus Stand:

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Contents

Table of Contents Foreword 7 1 Basics 8 1.1 Computer-aided call analysis 8 1.1.1 Presentation of calls 8 1.2 Overview of bat calls 12 1.2.1 Call types and variability of location calls 12 1.2.2 Catching sounds 15 1.2.3 Social noises 16 1.3 Measurement of bat calls 18 1.4 Application of criteria 23 1.4.1 Explanation of terms 23 1.4.2 Difficulty levels and depth of determination 24 1.4.3 Treatment of results from automatic species identification programs 26 1.4.4 Requirements for the application of the vocal determination criteria 26 1.4.5 Procedure in practice 28 2 Identification Criteria for Species and Groups 29 2.1 The Noctule - Nyctalus noctula 30 2.1.1 Overview 30 2.1.2 Location calls 30 2.1.3 Social calls 32 2.1.4 Distinctive call types 33 2.1.5 Criteria for verification of species 33 2.2 Leisler’s bat - Nyctalus leisleri 34 2.2.1 Overview 34 2.2.2 Location calls 34 2.2.3 Social calls 36 2.2.4 Distinctive call types 37 2.2.5 Criteria for verification of species 37 2.3 The Parti-coloured bat - Vespertilio murinus 38 2.3.1 Overview 38

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2.3.2 Location calls 38 2.3.3 Social calls 40 2.3.4 Distinctive calls 40 2.3.5 Criteria for verification of species 40 2.4 The Serotine - Eptesicus serotinus 41 2.4.1 Overview 41 2.4.2 Location calls 41 2.4.3 Social calls 43 2.4.4 Distinctive calls 44 2.4.5 Criteria for verification of species 44 2.5 The Northern Bat - Eptesicus nilssonii 45 2.5.1 Overview 45 2.5.2 Location calls 45 2.5.3 Social calls 47 2.5.4 Distinctive calls 48 2.5.5 Criteria for verification of species 48 2.6 Savi’s pipistrelle bat - Hypsugo savii 49 2.6.1 Overview 49 2.6.2 Location calls 49 2.6.3 Social calls 51 2.6.4 Distinctive call types 52 2.6.5 Criteria for verification of species 52 2.7 Kuhl’s and Nathusius’ pipistrelles - Pipistrellus kuhlii and P. nathusii 53 2.7.1 Overview 53 2.7.2 Location calls 53 2.7.3 Social calls 56 2.7.4 Distinctive call types 58 2.7.5 Criteria for verification of species 58

2.8 The Common pipistrelle - Pipistrellus pipistrellus 59 2.8.1 Overview 59 2.8.2 Location calls 59

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2.8.3 Social calls 61 2.8.4 Distinctive call types 62 2.8.5 Criteria for verification of species 62 2.9 The Soprano pipistrelle - Pipistrellus pygmaeus 63 2.9.1 Overview 63 2.9.2 Location calls 63 2.9.3 Social calls 65 2.9.4 Distinctive call types 66 2.9.5 Criteria for verification of species 66 2.10 The Brown and the Grey Long-eared Bat - Plecotus auritus and P. austriacus 67 2.10.1 Overview 67 2.10.2 Location calls 67 2.10.3 Social calls 69 2.10.4 Distinctive call types 70 2.10.5 Criteria for verification of species 70 2.11 The Barbastelle- Barbastella barbastellus 71 2.11.1 Overview 71 2.11.2 Location calls 71 2.11.3 Social calls 73 2.11.4 Distinctive call types 74 2.11.5 Criteria for verification of species 74 2.12 The Greater Horseshoe Bat - Rhinolophus ferrumequinum 75 2.12.1 Overview 75 2.12.2 Location calls 75 2.12.3 Social calls 75 2.12.4 Distinctive call types 76 2.12.5 Criteria for verification of species 76 2.13 The Lesser Horseshoe Bat - Rhinolophus hipposideros 77 2.13.1 Overview 77 2.13.2 Location calls 77 2.13.3 Social calls 78

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2.13.4 Distinctive call types 78 2.13.5 Criteria for verification of species 78 3 Final remarks 79 4 Literature 79 5 Appendix 81

6 Bayerisches Landesamt für Umwelt 2020 Forword

Foreword New techniques for recording and evaluating ultrasound calls from bats have led to a boom in this method of detection in the past ten years. Automation of analysis and evaluation lead to the possibility of surveys of the bat fauna such as long-term acoustic recording and the monitoring of difficult to reach locations (e.g. nacelles of wind turbines). The resulting abundance of new data and the temptation of automated evaluation make it imperative to set up criteria for how such acoustic evidence of bats should be professionally evaluated and thus assessed in terms of nature conservation.

Bats, like other mammals, have different repertoires of vocalizations that vary depending on behavioural or environmental factors. The quality of a recorded call also depends on physical and atmospheric conditions, and there are also large overlaps in the call repertoire between species. It follows that not all calls of the different Bat species are easy to identify and in many cases even impossible. This guide is intended to help all users dealing with acoustic evidence to critically check their own measurements or submitted recordings. Characteristic call types of the species are presented, which can be reliably identified on the basis of objectively measurable criteria. If these prerequisites are met, an acoustic proof of species can be regarded as secured. It is not the intention of this guide to provide methodological information for evaluating acoustic examinations or for assessing the activities of the bats at the location of the recordings. See, for example, the detailed publication by Runkel & Gerdes (2016).

This guide is the continuation of the "Criteria for the Evaluation of Species Based on Sound Recordings ” (Hammer et al. 2009). In contrast to the previous version, it does not contain any special criteria for dealing with automatically generated species determinations, e.g. with the programs batIdent (ecoObs, Nuremberg) or batScope (Swiss Federal Research Centre for Forest, snow and landscape, WSL). Since their susceptibility to errors is high, automatically generated species diagnoses must always be checked. This also applies to automatic identification results of species that are recognized relatively reliably by automatic analysis. The accuracy of these should be checked at least on a random basis. Compared to the previous "criteria for the evaluation of species evidence based on sound recordings" (Hammer et al. 2009), this new version not only describes characteristic calls but also the different types of calls of the species, described as comprehensively as possible. If species use different call types, these are dealt with and presented separately in the species chapters in order to make it easier to compare across genera. As far as characteristic social calls are known, these are also described. In order to provide a complete overview of the call repertoire of the species, frequent but undetermined social calls are shown in the appendix.

Almost all bat species native to Central Europe are treated. Species such as the pond bat are also listed that have not (yet) been found in Bavaria. This makes the guide applicable throughout Germany and northern Europe. Species with a southern European distribution focus, which partly expand their area to the north due to climate change, have only been taken into account if they have already established themselves north of the Alps (Savi’s and Kuhl’s pipstrelles). Species that so far show no strong tendency to spread to the north are not taken into account (Schreiber’s bat, alpine long-eared bat, European free-tailed bat, Mediterranean horseshoe bat, lesser mouse-eared bat).

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1 Basics The criteria are applied by measuring the bat calls on the computer using signal analysis programs. One speaks nevertheless of a manual determination, since the measured values, in contrast to the fully automated analysis with the measurement cursor, have to be determined visually by the user and the determination is not carried out by means of statistical discrimination algorithms. The final species diagnosis is therefore the responsibility of the processor. The next chapters explain the basics of signal analysis required for this. 1.1 Computer-aided call analysis In addition to special programs that have been developed to measure bat calls, non-specific sound analysis programs can also be used, provided they can process the high frequencies of the ultrasound recordings. The following programs are often used to analyze bat calls (without claiming to be complete):

 batSound (Pettersson Elektronik AB)  bcAnalyze (ecoObs GmbH)  batScope (Swiss Federal Institute for Forest, Snow and Landscape Research, WSL)  batExplorer (Elekon AG)  SASLab Pro (Avisoft Bioacoustics) Not all programs have the same functionality. Some have been developed for the evaluation of special sound formats that are used exclusively by certain recording devices. It is therefore advisable to compare the specifications of the programs before buying. Some programs can automatically determine measured values. However, these must be able to be checked manually since incorrect measurements can occur. 1.1.1 Representation of calls The simplest representation of sound is the oscillogram. Here the signals are displayed as oscillations around a zero line. This graph shows the change in sound pressure over time and is ideal for measuring the length of a bat call.

The Fast Fourier Transformation (FFT) is usually used to determine the frequencies involved (see Runkel & Gerding 2016 for more detailed explanations). Further calculations lead to the spectrum, which shows the distribution of the sound intensity over the frequencies. This display is used to read the loudest frequency of the call: the main frequency (frequency of maximum energy). In contrast to the spectrum, which contains no temporal information, the Sonagram shows the course of the frequencies over time (Fig. 1). The volume of the frequency ranges is shown in the Sonagram in color or in shades of gray.

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Fig. 1: Representation of a call as an oscillogram, sonagram and spectrum

A standard setting of the FFT window size and overlap (Harris window) is recommended for the display of the sonagrams, which does not represent the call too compressed or too far apart (Fig. 1). As a rule of thumb, a call is well depicted when its "height" corresponds approximately to its length.

To ensure recognition of the forms of calls, the appropriate settings should be retained. An FFT of 1024 with an overlap of 96% is recommended as the default setting (Harris window). In the case of short, frequency-modulated signals (e.g. short-range calls of the pipistrelle bat, Myotis species), it may make sense to deviate from this standard setting in order to map the call (Kopsinis et al. 2010). For example, to get a better time resolution, the FFT can be reduced to 512 (Fig. 2). Basically, it is important to choose the largest possible window (called FFT size in the programs) and a high overlap.

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Fig. 2: Left sonagram: optimal representation of a call falling in frequency; middle and right picture: unsuitable pictures

In order to be able to compare the shape of the calls better, one should always choose the same sonagram settings for similar call types. The following factors influence the representation of a signal in the sonagram and must be taken into account accordingly (see also Runkel & Gerding 2016):

 The "sample rate" set when the sonagram was created must correspond to that of the recording device, otherwise the frequencies will not be displayed correctly.  Colour and contrast influence the measurability of parameters in the sonagram. They should be set so that the background noise is just barely noticeable. The creation of sonograms is sometimes very different between different signal analysis programs. Names for setting parameters and functionalities can differ considerably. Even if comparable parameters are selected, the appearance of the sonagrams can differ significantly. The user may have to experiment a little to find optimal and comparable settings.

In the species description of this guide, all sonagrams were created with bcAnalyze and mostly with the following settings (Fig. 3). The settings are noted at the bottom of every sonagram:

 Short, frequency-modulated calls up to about 8 ms in length: FFT size 1024, 96.875% overlap, “7th-term Harris” window,  Long calls over 8 ms in length: FFT size 1024, 93.75% overlap, "7th-term Harris" window

Fig. 3: Recommended sonagram settings for the bcAnalyze program for (A) short, frequency- modulated calls and (B) long, almost constant frequency calls: (A) FFT size 1024, 7th-term Harris window, 96.875% overlap; (B) FFT size 1024, 7th-term Harris window, 93.75% overlap

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In the following nyctaloid and pipistrelloid species, the sonagrams of the qcf and fm-qcf calls are shown with an FFT of 1024 and an overlap of 93.75%. The shorter fm calls are shown with an overlap of 96.875% so that they can be compared with sonograms of fm calls from the Myotis species. The appropriate settings for social calls can deviate further so that they can be displayed meaningfully.

A call cannot be displayed and evaluated well without a sufficiently high recording quality. The recording quality initially depends on some situation-related factors such as the volume of the incoming calls (i.e. the distance of the bat to the microphone), the direction of the sound beam, the flight direction of the animal (Doppler effect), the attenuation due to vegetation and other obstacles (clutterness) and depending on the weather (e.g. air humidity). From a technical point of view, the quality of the signal results primarily from the signal-to-noise ratio, which is dependent on the device and cannot be influenced. The greater the amplitude (volume) of the call compared to the background noise, the higher the signal quality. This differance can be seen in the oscillogram. As a rough rule of thumb, one can say that the amplitude of the calls should be 10 times the noise.

The amount of noise compared to a defined signal depends on the recording technique. The gain of the system must be considered separately. If a signal is amplified, this affects noise and bat calls alike. It makes sense to use a setting in which the noise is clearly visible in the oscillogram but not too high (around 2–5% of the maximum deflection). Exaggerated amplification has no advantages and often leads to overdriven bat calls. Overloading occurs when the microphone signal is louder than the dynamic range of the device allows when the file is saved. In the oscillogram you can see that the vibrations “bump” at the boundary and are cut off (Fig. 4).

Fig. 4: Sonagram representation of a call in a bad recording. The amplitude of the noise is very high in relation to the call. This is also overdriven, which creates a noise band (horizontal). The front part of this Myotis call can only be guessed at as a slight shadow. In addition, loud echoes partially overlay the call.

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Overlapping echoes should be avoided, as this will mask the calls, especially for flat calls. When recording, the device should therefore be as high as possible above the floor and not too close to other reflective structures. The sound must be able to reach the microphone directly. If the device / microphone is installed in boxes for protection against water or provided with other rain protection, this often results in recordings that cannot be evaluated (Runkel & Gerding 2016).

1.2 Overview of bat calls

1.2.1 Call types and variability of location calls Bat calls of different species differ in particular in terms of volume, the frequencies used, as well as the duration and shape of the frequency-time curve. These differences arise from variation of the hunting strategy, structure of the preferred habitat, certain flight and behavioural situations and to the type and size of the prey. While the volume of the original call can no longer be reconstructed from a recording (unless you know the exact location of the bat with every call), the other parameters can be determined from the signals.

The locating calls of the native bat species are tonal. This means that the entire call is dominated by one frequency (main frequency). This can be varied by the bat depending on the situation. Sometimes one or more overtones can also be identified, which correspond to a multiple of the fundamental (1st harmonic) (Fig. 5). As a rule, the fundamental frequency is clearly louder than its overtones. Only the horseshoe bats (Rhinolophus) emphasize the first overtone (2nd harmonic). Only the loudest harmonic is decisive for the measurement of frequency parameters.

The calls of some species show pronounced overtones, some of which are just as loud or even louder than their fundamental vibrations (e.g. within the genera Plecotus and Rhinolophus; see Fig. 5). In the literature, the presence of clear overtones is often regarded as relevant to the determination. In practice, however, this feature is only of limited use, since the calls contain almost all types of overtones, which are also recorded if the animal calls close enough to the microphone. In addition, the intensity of overtones is strongly dependent on physical and technical factors such as atmospheric attenuation (air temperature, humidity) and the microphone frequency response. Artificial harmonics can also arise in the recording device (Fig. 6) or by processing on the computer. As a result, comparisons with the literature are only possible if exactly the same recording equipment is used and the same conditions prevailed during the recording.

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Fig. 5: The genera Rhinolophus and Plecotus use calls with pronounced overtones. For the horseshoe bats, the 2nd harmonic (first overtone) is even louder than the fundamental vibration

Fig. 6: Incorrect harmonics (“subharmonics”: undertone of an overtone) and other artefacts (e.g. mirroring) due to overdrive when recording.

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Depending on their shape, different types of location calls can be distinguished (Fig. 7):

Constant-frequency calls (cf) are present if the frequency does not change over the course of the call. In Central Europe, this is particularly the case for the horseshoe bats, although strictly speaking they should be called fm-cf-fm calls, since the long, constant-frequency middle range begins with a short frequency-modulated upward swing and ends with a short frequency-modulated downward swing.

Species of the genus Nyctalus, Vespertilio, Pipistrellus and Hypsugo often use calls that are not completely constant frequency, but decrease minimally in the course of the call. Here one speaks of quasi-constant frequency calls (qcf).

Species that use qcf calls in open airspace adapt their calls in narrower flight spaces, because there are more echoes here: the signals become shorter and higher-frequency. At the beginning of the call there is a steeply falling part of the frequency. This frequency modulated (fm) beginning is followed by a flat qcf part. This form is called a fm-qcf call.

In particularly narrow flight spaces and close to structures, almost all species can generate calls that no longer contain any qcf part. They are then pure fm calls. Species of the genera Myotis and Plecotus use this call type almost exclusively.

Fig. 7: Different call forms of native bat species and their allocation to the call types

The Barbastelle (Barbastella barbastellus) is a special case. It calls alternately with two types of calls: the first is a very short and narrowband frequency modulated call; the second type of call is somewhat higher in frequency and usually shows a qcf part at the beginning and then falls in frequency (qcf-fm).

Since the call types in this guide play an important role in identification, they must be precisely defined. Unfortunately, different authors use the terms differently, and in practice it has become common practice to take qcf calls in particular much further than originally defined. Schnitzler & Kalko (1998) define a slope of 0.4 kHz per millisecond as the boundary between fm and qcf calls. Skiba (2009) and Barataud (2015), on the other hand, describe all calls that do not have a bandwidth of more than 5 kHz as qcf calls, regardless of the duration. The latter definition is very general and not helpful if you want to describe different parts of a call. The definition by Schnitzler & Kalko (1998), on the other hand, is very narrow and in practice lies in the area of measurement inaccuracy. The following stipulations therefore apply to these guidelines.

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The term slope means the amount of the slope (regardless of whether the call increases or decreases). To calculate the slope, the spectral bandwidth (frequency range: highest minus lowest frequency) is divided by the duration of the relevant call segment, or the entire call.

 cf section: slope < 0.1 kHz/ms

 qcf section: slope ≥ 0.1 and < 1 kHz/ms  FM section: slope ≥ 1 kHz/ms

 cf call: average slope of the call < 0.1 kHz / ms  qcf call: average slope of the entire call is ≥ 0.1 and <1 kHz/ms

 fm-qcf call: the call contains fm and qcf sections, each of which is at least 1 ms long. The average slope of the entire call must be ≥ 1 kHz, otherwise it is still a qcf call

 fm call: the call does not contain any sections over 1 ms in length, the slope of which is < 1 kHz/ms Almost all locating calls from native bats can be assigned to these call types relatively easily. The species that use qcf calls can often only be determined if they utter long and flat calls. Shorter and steeper calls of these types are much more difficult and often cannot be clearly classified. Therefore, the criteria presented here are structured so that qcf calls, fm-qcf calls and fm calls are treated individually for species that use different call types. 1.2.2 Catching calls In addition to the calls that are used for orientation purposes only, feeding buzz and social calls should also be mentioned. Calls are made when a bat approaches an insect and seizes it. Such call sequences occur quite rarely compared to normal search flight calls. They can be recognized by the fact that call lengths and call intervals are greatly reduced. For most species, three phases can be clearly distinguished (Fig. 8). First, the bat approaches the insect, the calls are frequency-modulated ever shorter and shorter. These calls still correspond to the usual location calls of the type close to structures and objects. This is followed by very short and steep fm calls in the tracking and final phases, which are characteristic of the actual catching process. In the last phase, the frequency of the calls drops abruptly. This is believed to be an adjustment that enlarges the sonic beam at the last moment before catching to counter the evasive action that hearing insects use when exposed to loud ultrasound (Jakobson & Surlykke 2010).

Fig. 8: Feeding buzz of a Leisler’s bat, which is clearly divided into three phases. There is usually a short break before the final buzz (I + II).

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Capture calls are not very species-specific and are quiet, which is why they are rarely received. For these reasons, they are not suitable for species identification and are not further considered in the criteria. Calls from the approach phase that are not too short can still be measured and determined. In general, very short calls (close to structures) are not very specific for almost all species. Calls shorter than 2 ms (genus Myotis) or 3 to 4 ms (Nyctalus, Eptesicus, Vespertilio, Pipistrellus, Hypsugo) are not used for the determination. Only the calls of the genera Barbastella and Plecotus are so specific that even very short signals can be easily determined. 1.2.3 Social calls Social calls are only relevant to a small extent. This is mainly due to the fact that little has been studied so far and that they occur in very different ways in some species. They are mostly rarely and only expressed in special situations and therefore only recorded sporadically. This happens most regularly with the species of the genus Pipistrellus, in which, for example, the males undertake courtship flights in summer and call in the process. The calling type and the context can usually hardly be determined in the field and on the recordings. Another problem is that many species can use quite similar types of social calls. Within species, call types are also very variable and often individually shaped (Pfalzer & Kusch 2003).

Social calls are almost always easy to distinguish from location calls because they mostly

 have lower end frequencies,  are longer,  show an unusual shape in the sonagram,  often consist of several elements,  are multiharmonic or atonal,  are not repeated regularly (at least not at similar intervals to the location calls). However, not all of these points will apply equally to a specific call type.

A uniform classification of the different types of social calls does not yet exist. If their meaning is known, they are usually named accordingly, such as distress calls, courtship and encounter calls. For some calls, the name after the hearing impression has become common. Skiba (2009) writes, for example, of "humming calls" or "trills". Pfalzer (2002) also speaks of "trill-like" calls. In addition, he roughly differentiates between the following types of calls according to the auditory impression or their form: “croak”, “bow calls”, “double calls” and “complex” calls. Most calls, which Skiba (2009) describes as trills, are assigned to complex calls in Pfalzer (2002). For each type, Pfalzer (2002) also introduces alphabetical abbreviations for each type of call observed.

The present criteria do not work out a separate classification of the types of social calls. In the following, they are only roughly classified into the categories trills, double calls and bow calls. Only when the function of a call is known is it mentioned (e.g. courtship calls from the noctule and the common pipistrelle).

Trills are easy to recognize after training because they consist of several, quickly repeating, frequency-modulated parts. The elements are often arched in the sonagram, but can also be connected in waves (Fig. 9). Such calls occur in many species. They are often uttered as threatening or courtship calls of Nyctalus and Pipistrellus species in the field.

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Fig. 9: Three different types of social and location calls from Leisler’s bats meeting in the hunting habitat.

A common type of call is the so-called “bow call”, which is usually uttered as a single tone. Its frequency-time profile is reminiscent of long location calls. Almost all native species have such calls in the repertoire. In the species of the genus Myotis, it is the most frequently observed social call. However, not all bow calls are easy to identify. They often have smooth transitions to location calls. Fig. 10 shows bow calls of the whiskered bat (Myotis mystacinus) in front of a nursery roost. In this sequence, no calls are the same in form and frequency response.

Fig. 10: Bow calls of two or three whiskered bats (Myotis mystacinus) flying in front of a nursery roost. The call distances are shown in abbreviated form.

Many species emit a special form of bow call, mainly in the roosting area. These are short, steep fm calls that are very reminiscent of short location calls. Such calls are extremely variable and mostly unidentified (especially when several animals are calling at the same time). Fig. 11 shows a sequence of swarming Leisler’s bats in front of a quarter in the forest. In addition to long trills, only short fm calls are used. Such a recording leaves open how many animals were present and which calls were used for orientation and which in a social context.

Fig. 11: Swarming Leisler’s bats in front of the roost. In addition to long trills, short fm calls can also be seen, some of which are social calls and some of which are location calls.

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1.3 Measurement of bat calls Numerous factors can affect the results of bat call analysis. In addition to physical influences (humidity, temperature, echoes), technical influences such as the sample rate and microphone properties are particularly worth mentioning. Changes in the microphone properties are the reason why they should be calibrated regularly. The settings of the evaluation programs can also have a strong influence on the evaluation and measurement of the spectra and sonagrams. Runkel & Gerding (2016) give a good overview of these pitfalls.

The following explains which measurement values are suitable for which call types and how they can be measured (standard parameters). Section 1.4.4 also lists the prerequisites that are necessary for the application of the criteria.

Unfortunately, there is no uniform nomenclature for many measured values. Different authors use different names and abbreviations for the same measured value. The same term is often used to refer to different parameters (e.g. "main frequency"). In the following, the measurement values essential for the location calls of the Central European species are described and the most common and least misunderstood names and abbreviations are used (see Fig. 12 and Fig. 13).

• FmaxE Frequency of maximum energy (= main frequency); Frequency with the most energy over the entire course of the call; is determined in the spectrum

• Fstart Start frequency; Frequency at the beginning of the call

• Fend End frequency; Frequency at the end of the call

• Fmin Minimum frequency; lowest frequency in the call process; Fmin and Fend often coincide

• Fmax Maximum frequency; highest frequency in the call history; usually corresponds to the start frequency

• Fknee Knee frequency; Frequency at the transition between the steeper initial part of the call and the flatter main part

• FMk Frequency at the “Myotis-knick”; Kink at the end of calls from Myotis species, after which the frequency drops sharply; behind the kink is the so-called “myotis tail”

• Fc Characteristic frequency; the lowest frequency in the flat main part of the call (for bowl-shaped calls, the slope is zero here); if there is an up or down hook at the end of the call, Fc is always in front; only useful for qcf or fm-qcf calls • B Bandwidth; Frequency range that the call sweeps from the maximum to the

minimum frequency, Fmax - Fmin • D Duration; Call length

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Fig. 12: Location of various shape parameters. The “myotis-knick” is only important for fm calls. In contrast, a clear knee can occur with fm and fm-qcf calls. The characteristic frequency is an essential determinant for all calls that have qcf components.

Fig. 13: Different standard parameters of a bat call. The duration is best measured in the

oscillogram. The main frequency FmaxE must be determined in the spectrum.

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The measurement parameters FmaxE, Fstart, Fend and D are the values most frequently used in the literature. The frequency of maximum energy FmaxE is often used in particular for the description of cf and qcf calls. With these types of calls, FmaxE mostly (but not always) corresponds to the characteristic frequency Fc (see below). The value of FmaxE is measured in the spectrum and indicates the frequency with the highest energy component. To do this, the entire call must be analyzed with a single window (rectangular window). The marking should go a little beyond the beginning and end of the call (note: some programs do not calculate with a window). FmaxE is also used in the literature to describe fm calls, although this parameter is basically unsuitable for this. In the literature there are a number of different names and abbreviations for FmaxE (such as: mean frequency, main frequency, F(max) or peak frequency), which are often ambiguous and sometimes measured differently. This value is usually irrelevant in this guide.

For fm calls, Fstart and Fend mostly correspond to Fmax and Fmin. However, this is not the case with other sound types. The start frequency is an important, but not always determinable criterion, especially for species of the genus Myotis. The quiet and high start frequencies are particularly influenced by atmospheric attenuation, the microphone frequency response and the sample rate of the devices. The latter must be at least 400 kHz in order to still be able to reasonably represent the highest values (for the species in Central Europe sometimes up to over 180 kHz). In order to create sonagrams with a high temporal resolution that still allow the shape to be assessed even with short calls, a sampling rate of 500 kHz is generally recommended for Myotis species. The loudest calls should be used to measure the start frequency. If the call in the sonagram starts abruptly and loudly, you can be quite sure that you can see the actual start. With Myotis species, the call often shows a small tick that defines the beginning (Fig. 14). Even if the actual start frequency cannot be determined with certainty, a measurement can be useful to exclude certain types. If the measured value for a Myotis call is clearly above 100 kHz, it is very likely, for example, that it is not a Daubenton’s bat.

Fig. 14: Call of a Daubenton’s bat with a clear tick at the beginning of the call

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Since sonagrams have a rough temporal and spectral resolution, the call is displayed with a certain degree of blurring. In the picture, the sonagram appears as a broad, thick line. If the blurring is uniform, it can be assumed that the real frequencies are in the middle of the call image (see dotted line in Fig. 15 B). This is relatively irrelevant in the call process itself, but at the beginning and at the end of the call it leads to them being blurred and not being able to be delimited exactly from the background. This makes it difficult to measure the exact start and end frequency. It can help to imagine a circle, the diameter of which corresponds to the thickness of the “blurred” frequency-time curve. The frequency is then measured in the middle of the circle. This measuring point can be confirmed or checked using the oscillogram. With the help of these tricks, especially in the genus Myotis, it can be avoided to determine start frequencies too high and end frequencies too low (Fig. 15).

Fig. 15: In the sonagram, the frequency-time curve can only be displayed “out of focus” (A). It can be difficult to determine the exact start and end frequency here. In these examples, the blue dots in Fig. B show the actual course of the frequency over the course of the call. If you mark the beginning and end of the call (green line) in the oscillogram, the measured values in the sonagram must lie on this line. A circle (shown in red) with the diameter of the “blurred” part of the call can help to determine the exact measured value for the beginning and end of

the call (Fstart and Fend).

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At the end of the call, very quiet elements can sometimes be recognized, which differ significantly in shape and frequency from the courses otherwise found. There are even end pieces that look forked in the sonagram (e.g. the right call in Fig. 15). These are probably non-functional elements that arise when the glottis is closed in the larynx of the bat. They are not relevant for the determination and should not be measured.

The shape parameters of a call (Fig. 12) can only be used to determine certain call types and are not always clearly recognizable. However, they are far less distorted by physical and technical influences than the standard parameters.

The calls of different species, even from different genera, often show a similar division of the call history (see Fig. 13). After an initial part that drops sharply in frequency, a flatter main part follows (Gannon et al. 2004). The authors refer to the transition point between the two parts as the knee. Both fm calls and fm-qcf calls can have such a knee. However, this is not always (clearly) recognizable and measurable, which is why this parameter (Fknee) has so far not established itself as a distinguishing feature for European bats. The knee is explained in this guide because it is particularly important for the determination of some types of Myotis. Make sure that the shape of the call is clearly kneeled (significant change in slope) and if so, whether the two parts are linear or curved.

Some Myotis calls show a kink in addition to the knee. It lies in the back part of the call between the flatter main part and the end part, which drops steeply in frequency, the so-called “Myotis tail”. This

“Myotis-knick” (see FMk Fig. 16) is often prominently developed and easy to measure. Measurements are taken at the point with the greatest change in slope (not at the beginning or end of the bend). The tail that follows can be of different lengths. Among other things, the direction from which an animal was recorded has an influence on its shape. In the case of steep, linearly falling call types, however, neither Knee, Myotis-knick nor a detached tail can be seen.

Fig. 16: Measurement of the FMk frequency at the “Myotis-knick”.

The Myotis-knick is important for the determination of species within the genus Myotis, since it is much more constant than the final frequency. So that the shape can be examined even with short calls, the recording must have a high temporal resolution. If the sampling rate of the recording is less than 400 kHz, the shape parameters are not always recognizable.

Calls from species of other genera can also have a sloping tail at the end of the call (in this guide, the kink is also referred to as “Myotis-knick” for these species). When it comes to short fm calls, the FMk can be important for the separation of calls from the genus Myotis.

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Otherwise, it is not relevant for species identification for these species, since the form of the call is very variable. For example, the frequency of the end piece can increase instead of falling (e.g. in the Pipistrellus genus).

For all types that use qcf or fm-qcf calls, the characteristic frequency Fc is the essential and often sufficient parameter for the determination. This value was introduced with the AnaLook software (Chris Corben, Titley scientific). However, the original definition (see Gannon et al. 2004) is inaccurate and cannot be used clearly for many calls, which is why it should be used in a slightly modified form: Fc is the frequency value at the flattest point of qcf or fm-qcf calls. The calls must therefore have at least one section that is almost constant in frequency. This measuring point is always in the main part of the call, usually immediately before the call finally snaps up or down again (see Fig. 12). If the qcf call drops evenly in frequency, the value is measured at the lowest point of this piece before the slope changes (in contrast to FMk).

The duration D of the call is best measured in the oscillogram. The measurement can be difficult if qcf calls overlap with a strong echo. If a clear overtone is formed, the length of the call can usually be better recognized from this. Duration and bandwidth, B are mainly required to determine the slope of the call and thus the type of call (Fig. 17).

Fig. 17: The slope of the call (or a section) can be determined quite easily in bcAnalyze by drawing a rectangle from the highest to the lowest point of the call with the cursor. The difference in frequencies is now divided by the duration.

1.4 Application of the criteria

1.4.1 Explanation of terms Different types of calls are shown and described for each species in the species chapter. A figure also shows a call sequence that is as characteristic and easy to identify as possible. If available, characteristic call features are specified for each call type. These are species-specific characteristics that are relevant for the identification. As a rule, only some of the individual calls meet the criteria (so-called characteristic and distinctive calls), since the features do not have to occur with all calls in the call spectrum of the species or within a call sequence. If they are available, however, they provide clear indications of the respective species.

The identification criteria (criteria for the species identification) must be fulfilled so that the species identification can be considered as secured. The decisive factor is usually a defined minimum number of characteristic calls or sequences and no simultaneous or timely occurrence of confusion

Bayerisches Landesamt für Umwelt 2020 23 Basics types. These criteria are derived from many years of experience and are adapted to the species. They represent a further development of the sound analysis criteria of Hammer et al. (2009).

If a certain number of typical calls or sequences must be present, this criterion relates to a maximum of one detection night at a specific location in the case of a stationary detection or along a transect route in the case of a mobile detection. By sequence (= recording) is meant a single sound or a sequence of several location sounds that are saved as a file and belong to an animal. A call is a single sound of a sequence.

Confusion species are species that use very similar calls and overlap in their call repertoire. For verification of species, they may not occur together in time (example: a call sequence with references to the Alcathoe bat within several sequences of whiskered bats a few seconds apart). Unless otherwise stated, there should be at least a two minutes interval between evidence of two similar calling species. A sequence is only a potential confusion type if there are distinctive call features of this type. Sequences whose determination ends at group level are not taken into account here. 1.4.2 Difficulty levels and depth of determination In addition to the correct application of the criteria, a self-critical way of working when analyzing bat calls is necessary, as well as the knowledge that there are many calls and call sequences that cannot be identified. In general, great caution is required if there are only a few sequences and/or calls for identification and/or if the recordings are of poor quality or are quiet. This guide specifies a difficulty level for the manual identification of echolocation calls for each species (Tab. 1). The criteria presented here are conservative, i.e. strict. Nevertheless, the experience of the processor will have an impact on the certainty of identification..

The following levels of difficulty are distinguished:

• layperson I (*) Identification easy and clear for the layperson, • layperson II (**) Identification after familiarization easily and unambiguously, • Expert I (***) Identification for the most part easily and unambiguously after familiarization but there are overlaps with other species, • Expert II (****) Identification largely difficult even after familiarization; some call types can still be identified with certainty, • Expert III (*****) Identification very difficult or impossible even after training; tends to be only possible at genus or group level or only when all confusion types are absent. If calls or sequences cannot be assigned to any type because characteristic features are missing, experience is lacking or the level of difficulty is too high, the determination should only be made to genus or Group level. The groups and subgroups listed in the table are borrowed from the step-by- step automatic identification by batIdent (see ecoObs 2020) and have largely become naturalized in Germany.

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Tab. 1: Difficulty level (S) of manual identification of typical sequences of location calls (for definition of levels see above).

Species, genus or group Abbr S Genus Rhinolophus R. hipposideros Rhip * R. ferrumequinum Rfer * Genus Plecotus P. Auritus / Austriacus Plec *** Nyctaloid Nyctaloid medium frequency Vespertilio murinus Vmur **** * Nyctalus leisleri Nlei **** Eptesicus serotinus Eser **** Nyctalus noctula Nnoc *** Eptesicus nilsonii Enil *** Pipistrelloid Pipistrelloid Hypsugo savii Hsav *** low Pipistrelloid medium P. kuhkii / Pkuh ** frequency frequency P. nathusii Pnat Pipistrelloid P. pipistrellus Ppip ** high P.pygmaeus Ppyg ** frequency Genus M. myotis Mmyo *** Myotis M. alcathoe Malc *** M. emarginatus Mema **** M. dascyneme Mdas **** M. natteri Mnat ** Myotis small / M.bechsteinii Mbec **** medium M. daubentoniI Mdau *** Whiskered bat M. brantii / mytacinus Mbra **** Genus B. barbastellus Bbar * Barbastella

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1.4.3 Treatment of results from automatic species identification programs In addition to the criteria for manual determination, the previous version of this guide also contained specifications for checking automatically generated determinations of the programs of the batcorder system (bcAdmin and batIdent, company ecoObs). This dichotomy will not continue because it has led to confusion. In order to obtain reliable determinations, at least individual sequences should generally be checked manually, also of common and easily determinable types. Although the software reliably identifies many species, incorrectly measured signals can lead to incorrect identifications despite a very high safety factor. Such incorrect measurements can be recognized relatively well with manual control. We have not yet had enough experience with other determination tools such as batScope, batExplorer or SonoChiro® to assess their suitability in practice. Since these basically use the same measured values and similar algorithms, a manual check is also required for these programs in order to reliably identify the calls.

In order to get a quick overview in bcAdmin of how safe the automatic determinations are to be classified, the creation of a species list with the option "Consider probabilities" helps (see Fig. 18). Very similar to the previous criteria, it is now being analyzed how many sequences of a kind are available with which probabilities. These results can then be used for targeted manual checking of the corresponding sequences in accordance with this guide. By combining the automatic call determination and manual verification, the risk of incorrect determinations can be minimized.

Fig. 18: Weighted species list in bcAdmin, taking into account the probabilities and number of sequences. It provides valuable information for targeted follow-up checks. 1.4.4 Requirements for the application of the acoustic criteria The identification criteria are aimed at all “skill levels” and should also be able to be used by laypersons without any previous knowledge. The application of the criteria should also be possible regardless of the recording technology and analysis software used. It is necessary to read and understand the chapters of this methodological guide thoroughly. In order to ensure the quality of the determination with this fairly open approach, some prerequisites must be met.

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• To determine the types of myotis, the microphone must be sufficiently sensitive to high frequencies up to approximately 150 kHz. At least for loud calls, you should be able to recognize the start of the call and the sampling rate of the recording devices must be at least 400 kHz for these types. • The acquisition hardware should be set so that the background noise is still clearly visible in the oscillogram, but does not exceed 5% of the full scale. Important: The internal amplification cannot be adjusted for all devices. It is not synonymous with the threshold. • The settings of the sonagram should be selected so that the background noise is just mapped. The sonagram settings should always be selected in accordance with Chapter 1.1.1. With short signals, a sufficiently high time resolution must always be set so that the shape of the calls can be recognized. • The call recordings must be of sufficient quality; Quiet calls cannot be identified for many species, as the high frequencies in particular may be missing. • As a rule, it is not possible to determine location calls directly at the roost, since calls in this situation often differ from location calls in the habitat (see, for example, the location calls of Leisler’s bat in Fig. 11); characteristic social calls are excluded from this. • Care should also be taken when determining location calls that have been recorded in roosts (attics, caves / galleries), since the quality of the recording is often not sufficient for a correct determination under the special reflection conditions. • No determination of recordings in which several animals / species with similar calls occur at the same time. It is then no longer possible to reliably assign the individual calls to an animal. • Only identify characteristic call sequences. Manual identification is often only possible at group level. In the case of difficult species, the experience of the processor can be decisive. In many cases, an identification is not possible. • Fully automated call identifications do not meet the professional standard. Even with common and/or easily identifiable species, at least manual evaluation of random samples is necessary. In general, the reliability of the evaluations increases with self-critical consideration. The majority of the sequences can usually not be clearly identified. Particular caution is required and additional experts must be consulted when it comes to recordings of species far outside their normal range or of particularly rare species. In such cases, acoustic proof of species should generally be handled critically and other methods of confirming proof of species, such as for example the catching of animals may be considered.

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1.4.5 Procedure in practice The following points should be taken into account in the work routine when identifying the calls:

• For reliable detection of a species, it is not necessary to check all the recordings during the night in question. As soon as the necessary criteria are met, the proof is considered to be secure.

• Review previous and subsequent sequences to identify types of confusion.

• It is not necessary to determine all measurement parameters for the identification of a species, but only the call characteristics that characterize each species.

• It makes sense to first take the longest recordings with the most and loudest calls. Short recordings with only a few quiet calls only need to be checked more closely if their could be a confusion or if there are no long recordings.

• Some programs offer the possibility to view many files one after the other in a file browser (SASLab Pro, bcAnalyze). This quick review helps find relevant files and identifiable call types. Social calls can also be searched specifically.

• Based on the results of an automatic determination, you can get an overview relatively quickly in order to specifically check possible species and types of confusion.

• Before considering individual measurements, you should view the entire sequence in an overview. Here you can see whether the sequence contains calls from more than one animal and whether there are call changes.

• For the measurement you should select calls that are as loud as possible but not overdriven at the same time.

• Examine both longer and shorter calls in a recording in order to better assess the call repertoire.

• With Myotis species, the maximum start frequency can best be recognized with short calls.

• Do not consider calls under 2 ms (Myotis, Plecotus, Barbastella) and 3 to 4 ms in length (other species) and no calls from the Final Buzz.

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2 Identification Criteria for Species and Groups The chapters are structured according to a uniform structure. After a brief summary, the location calls are described. A table lists the variability of the essential measured values for the individual call types. It also shows whether the call types can be determined and with which other types they are to be confused. Three levels of determinability are used:

• characteristic: The call type can be identified on the basis of characteristic features • partly characteristic: some characteristics of the call type can be identified based on characteristic features • cannot be identified: calls of this type cannot be used to identify the species. A sonagram of a typical call sequence of this type is then mapped (typical here, however, does not necessarily mean identifiable). The individual call types are described and placed in the context of the confusion types. For each call type, a figure shows different individual calls from different individuals to reflect the variability within this call type. These calls are sorted by length and frequency.

Frequent social calls are then described, with the focus on identifiable social calls. This means that there is no claim to completeness. However, additional social calls are shown in the appendix.

At the end of each section of the species, the distinctive call types (location and social calls) with their characteristic parameters are summarized and the criteria for a species validation are given.

For better comparability, the same sonagram settings were chosen for the same call types. Fm calls are displayed with an FFT size of 1024, 7th-term Harris window and 96.875% overlap. Fm-qcf, qcf and social calls are displayed with the same FFT size and the same window, but with 93.75% overlap. However, for space-saving reasons, the social calls are shown in the appendix with an 87.5% overlap. All recordings were made uniformly with a sample rate of 500 kHz.

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2.1 The Noctule - Nyctalus noctula Degree of difficulty according to Tab. 1: Expert I (***). 2.1.1 Overview The noctule can be easily identified using typical long qcf calls that are made in open airspace. Fm- qcf calls of noctules are similar to those of other nyctaloid species and can rarely be identified. Very short fm calls close to vegetation (e.g. in the forest) or when swarming in front of roosts are not characteristic. Social calls are often made in the roost, but also on the fly in the habitat. In particular, courtship calls and short trills can be identified. Other vocalizations are so variable that it is not yet possible to assess whether they can be identified with certainty. 2.1.2 Location calls The noctule prefers to hunt with loose contact to structures in open airspace and then uses characteristic qcf calls, which are lower in frequency than those of all other species in Central Europe (apart from the European free-tailed bat and the greater noctule, which can occur in the south and southeast of Central Europe). Alternating calls are usually emitted at different frequencies (“plip- plop” calls). The difference in the characteristic frequency Fc between the "plip" and "plop" calls is around 2 to 4 kHz (Fig. 19, Fig. 20).

Tab. 2: Areas for different measurements of the call types of the noctule; Extreme values are given in brackets.

Call type Fc (kHz) FMk (kHz) D (ms) Confusion types Determinability qcf (16)17–22(23) (10)15–30 Vmur, Nlei characteristic fm-qcf (19)20–29(30) 6–20 Vmur, Nlei, Eser partly determinable fm (24)26–30 3–7 Vmur, Nlei, Eser, Enil not determinable

Fig. 19: Typical sequence of the noctule with alternating "plip-plop" calls; the call intervals are shown shortened.

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Fig. 20: Selection of different qcf calls from the noctule.

The calls change into fm-qcf calls closer to the vegetation (forest edge, rides and clearings) (Fig. 21). A frequency change can also be seen on these calls. Longer calls usually only show a short fm part and, after a clear knee, a long qcf part. Shorter calls, in which the qcf portion accounts for less than half of the call, tend to be evenly curved. Such calls are similar to those of the serotine, while in the case of Leisler’s and parti-coloured bat, these calls usually show a clear knee. The fm-qcf calls of the noctule tend to be longer and deeper than those of similarly calling species. However, they are extremely variable and can therefore only be identified in exceptional cases if their characteristic frequency is below 21 kHz.

Fig. 21: Selection of different fm-qcf calls from the noctule

True fm calls express the type of localization (Fig. 22). This is usually the case in forest habitats, on rides and close to the roost. Such calls no longer show a qcf portion. Fm calls of the noctule cannot be distinguished from fm calls of other nyctaloid species from the genera Vespertilio, Eptesicus and Nyctalus.

In contrast to Myotis calls, these fm calls are much more variable in shape and frequency response. Such call sequences almost always contain longer calls that have a qcf end, which does not occur with calls of the genus Myotis. Especially when swarming around the roost, the location calls often turn into short, atypical fm social calls, which are then somewhat lower in frequency. There is a risk of confusion with calls of the long-eared species, which, however, show a lower starting frequency (usually below 50 kHz). In addition, on the one hand the call series with swarming noctules are much more irregular in rhythm and on the other hand the call types and frequencies are more variable.

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Fig. 22: fm calls of the noctule.

2.1.3 Social calls The species uses a variety of different social calls in the roost and in the hunting habitat, which are also recorded more frequently. Many of these calls are similar to those of Leisler’s bat but also of other species. The mating calls of the males are unmistakable, and are only uttered from the roost. These are very long qcf calls (30 to 90 ms), which can be somewhat frequency-modulated at the beginning and at the end; the flat part of these calls is around 13 kHz (see Skiba 2009 and Pfalzer 2002). It is a multi-harmonic call with a pronounced fundamental frequency (Fig. 23).

Fig. 23: Courtship call of the noctule; Since the recording device has attenuated low frequencies and thus the fundamental vibration, the first overtone wrongly appears to be the loudest in this recording.

The short trills are further identifiable social calls (Skiba 2009). These calls, consisting of several elements, are uttered in the hunting habitat and near the roost. There is usually a down-modulated fm signal at the beginning and at the end. In between there are one to four U-shaped elements, which frequently increase in frequency (Fig. 24). They can also be connected to one another and form a wave. The start and end elements are very variable in terms of shape and frequency and may be missing. Fmin of the first elements is usually between 18 and 25 kHz. Leisler’s bat also expresses a trill. However, the middle elements are mostly only frequency modulated downwards or only hinted U-shaped. They are also shorter and show a smaller bandwidth (see Fig. 30). The courtship trill of the Pipistrellus species, in contrast, does not contain clearly separated start and end elements. Furthermore, either the total length is shorter (usually less than 40 ms), the frequency is lower (Kuhl’s pipistrelle) or the individual elements are shorter (common and soprano pipistrelle).

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Fig. 24: Typical short trill of the noctule. For further types of trills, see Fig. 85 and 86 in the Appendix.

Noctules very often utter long fm-qcf calls that can have different meanings (e.g. calls for encounters or excitement) (Fig. 87 in the Appendix). These "location-call-like" to "arched" calls (Pfalzer 2002) are extremely variable and can occur as single calls, double calls or call series. The lowest frequencies of these calls vary between 11 and 25 kHz and their length is between 5 and 60 ms. Since the call types can flow smoothly into one another and other types also use similar “arched” calls, identification should be avoided.

2.1.4 Distinctive call types All qcf and fm-qcf calls, whose characteristic frequency is clearly below 21 kHz, are distinctive. Even "plip-plop" sequences, whose deep calls are between 21 and 23 kHz, can be distinguished from Leisler’s bat if at least the higher calls are frequency-modulated at the beginning.

Courtship calls are characteristic if the qcf calls are at least 35 ms long and have no downward fm part at the beginning. Short trills can also be identified if the middle elements are clearly U-shaped and/or they have a length of more than 6 ms and a bandwidth of more than 20 kHz. The first and last element must be clearly different from the middle syllables.

2.1.5 Criteria for verification of species • It is sufficient if there is a distinctive call (qcf call or social call), • In the case of alternating fm-qcf calls (“plip-plop”) at 21 to 23 kHz, there must be at least three sequences with a change of call and there must be no confusion in close proximity (+/- 2 minutes).

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2.2 Leisler’s Bat - Nyctalus leisleri Degree of difficulty according to Tab. 1: Expert II (****).

2.2.1 Overview Leisler’s bat shows a call repertoire similar to that of the noctule and can be identified on the basis of its qcf calls, but its fm-qcf and fm calls are not characteristic, since they show strong overlaps in the frequency range with all other "nyctaloid" calling types. The courtship call of male Leisler’s bats and short trills are typical of the species. Other "location call-like" to "arched" social calls are very variable and not suitable for species identification.

2.2.2 Location calls The call types are somewhat shorter and more frequent compared to the noctule. In addition, there are fewer and fewer alternating calls. The frequency difference between two “plip-plop” calls is usually only 1 to 2 kHz (see Fig. 25).

Tab. 3: Areas for different measurements of the call types of Leisler’s bat; Extreme values are given in brackets.

Call type Fc (kHz) FMk (kHz) D (ms) Confusion types Determinability qcf 21–26(27) (6)8–20 Vmur, Nnoc characteristic (24)25– Vmur, Nnoc, fm-qcf (4)5–16(18) determinable 29(31) Eser, Enil Vmur, Nnoc, fm (26)28–32 3–5(6) not determinable Eser, Enil

Fig. 25: Typical sequence of Leisler’s bat with alternating qcf calls; the call intervals are shown shortened

The lowest characteristic frequencies (Fc) of qcf calls are 21 kHz. If the characteristic frequency of the lower call of a “plip-plop” sequence (ie the “plop”) is in the range from 21 to 23 kHz, the two alternating calls are always real qcf calls. This distinguishes Leisler’s bat from the noctule, in which the higher call or both calls show a clearly frequency-modulated start in this frequency range. Leisler’s bat sometimes uses amazingly short qcf calls of around 6 ms in length (Fig. 26).

The fm-qcf calls cannot be identified (Fig. 27). They tend to be shorter and have a higher frequency than that of the noctule. The shape of these calls almost always shows a clear knee, while that of the noctule is rather evenly bent. However, this is not a clear identification criterion. In terms of shape and frequency, these calls are very similar to those of the particoloured bat.

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Fig. 26: Selection of different qcf calls from Leisler’s bat

Fig. 27: Selection of different fm-qcf calls from Leisler’s bat

The fm calls of Leisler’s bat are also undetermined (Fig. 28). All other nyctaloid species can call similarly. Especially in the vicinity of forests, only such short localization calls are often recorded. In such cases, it makes sense to search specifically for social calls.

Fig. 28: Selection of different fm calls from Leisler’s bat

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2.2.3 Social calls Leisler’s bat is just as call-happy as the bigger noctule and uses very similar types of social calls. However, the courtship calls of the males are unmistakable (Fig. 29). They are long qcf calls, which are 15 to 35 ms long, much shorter than those of the noctule. They also show a clear drop in frequency. The flat rear part of the calls is around 13 (10-18) kHz. These calls are made from the roost or in flight at regular intervals (0.5–2 seconds).

Fig. 29: Typical courtship call of Leisler’s bat

Another definable social call is the short trill (Skiba 2009). This call, consisting of several elements, is uttered both in the hunting habitat and close to the roost (Fig. 30). Similar to the noctule, there are clearly different downward modulated fm signals at the beginning and sometimes at the end. In between there are one to five shorter elements, which can either only be frequency-modulated downwards or be hook-shaped. They are shorter compared to the noctule and have a smaller bandwidth.

Fig. 30: Typical short trill of Leisler’s bat. For further types of trills, see Fig. 88 and 89 in the Appendix

Like the noctule, Leisler’s bat shows a large repertoire of long fm-qcf calls, which are interpreted as excitement calls. These “location call-like” to “arched” calls (Pfalzer 2002) are very variable and can occur as single calls, double calls or series of calls (Fig. 90 in the Appendix). The lowest frequencies of these calls vary between 11 and 25 (30) kHz and their length is between 5 and 70 ms. Their variability is also high, the call types can flow smoothly into one another. Since other species also use similar “arched” calls, an identification should not be made.

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2.2.4 Distinctive call types The type can only be identified with certainty if there are regular “plip-plop” calls. Then qcf calls with a characteristic frequency of 23 kHz and above are unmistakable.

“Plip-plop” sequences, whose deep calls are between 21 and 23 kHz, can also be distinguished from the noctule if both alternating calls are real qcf calls, ie do not have a clearly frequency-modulated start.

Courtship calls are characteristic if the qcf calls are not longer than 35 ms and initially have a downward fm part. Short trills can be identified if the middle elements are not clearly U-shaped and/or they have a length of less than 6 ms and a bandwidth of less than 20 kHz.

2.2.5 Criteria for verification of species • With "plip-plop" calls, there must be at least three sequences with regular call changes and distinctive qcf calls (together> 10 calls) and no confusion types may occur in close proximity (+/- 2 minutes).

• Social calls: either a typical short trill or a sequence with at least three courtship calls at regular intervals.

Bayerisches Landesamt für Umwelt 2020 37 Identification Criteria for Species and Groups

2.3 The Parti-coloured Bat - Vespertilio murinus Degree of difficulty according to Tab. 1: Expert III (*****).

2.3.1 Overview The species shows an extreme overlap in the repertoire of calls with other "nyctaloid" calling species. There are no unmistakable location calls, so that the species cannot be detected acoustically. Only the absence of certain types of calls of other types can give an indication of the species in the case of a large number of recordings. The parti-coloured bat makes social calls relatively rarely. The male courtship call is, however, typical of the species.

2.3.2 Location calls Tab. 4 shows an overview of the measured variables of the call types and the possibilities of confusion, and Fig. 31 shows a typical call sequence of the parti-coloured bat, which can be identified with a lot of experience.

Tab. 4: Areas for different measurements of the call types of the parti-coloured bat; Extreme values are given in brackets.

Call type Fc (kHz) FMk (kHz) D (ms) Confusion types Determinability cf &qcf 21–25(26) (10)12–26(30) Nlei, Nnoc Tends to be determinable Nlei, Nnoc, fm-qcf (22)23–30 4–14(16) not determinable Eser, Enil Nlei, Nnoc, fm (23)25–30 3–5(7) not determinable Eser, Enil

Individual calls of all call types cannot be differentiated from those of Leisler’s bat. The parti- coloured bat can only be excluded if Leisler’s bat shows regular calls ("plip-plop"). However, caution is also required here, since the parti-coloured bat does not utter regular “plip-plop” sequences, but can use very different calls in an irregular sequence within a sequence.

Fig. 31: Typical sequence of the parti-coloured bat with long qcf calls; the call intervals are shown shortened.

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Qcf calls between 21 and 25 kHz are quite typical for the parti-coloured bat (Fig. 32), and are often longer (> 20 ms) than those of Leisler’s bat.

Fig. 32: Selection of typical qcf to cf calls from the parti-coloured bat

The fm-qcf calls (Fig. 33) are very variable and closely resemble those of Leisler’s bat. As with this bat, the calls usually have a clear knee. You are uncertain. The same applies to fm calls (Fig. 34), which are usually only expressed very close to structures (e.g. in front of a roost).

Fig. 33: Selection of different fm-qcf calls from the parti-coloured bat

Fig. 34: Selection of typical fm calls from the parti-coloured bat

Bayerisches Landesamt für Umwelt 2020 39 Identification Criteria for Species and Groups

2.3.3 Social calls The parti-coloured bat expresses social noises much less frequently than species of the genus Nyctalus. Only the unmistakable courtship call of the males is relevant for identification (Fig. 35). After some very short and quiet fm elements there follows a call of about 20 ms, which is similar to bow calls of other types. However, the combination of the call elements is unique. The calls are uttered regularly every 0.2 seconds in flight.

Fig. 35: A sequence with two successive courtship calls of the parti-coloured bat (an echo can be seen behind the bow calls). In between there is a characteristic sequence of very short and quiet fm elements.

2.3.4 Distinctive calls As a rule, the parti-coloured bat cannot be reliably identified using location calls. There is a strong indication of the type when qcf calls between 21 and 25 kHz with a length well over 20 ms are present. However, the length of the calls can be difficult to measure if they overlap with a strong echo.

The courtship calls are typical when the individual elements are visible and the call is repeated regularly.

2.3.5 Criteria for verification of species • Location calls: not determinable; only absolute experts can tend to address the species with a large number of recordings and the absence of confusion. However, further methods are required for reliable species identification (e.g. net catch, roost search).

• Social calls: at least one typical sequence of courtship calls with intermediate quiet fm calls (see Fig. 35).

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2.4 The Serotine - Eptesicus serotinus Degree of difficulty according to Tab. 1: Expert II (****).

The species is characterized by the fact that it shows no call changes in the sequences. Frequency, form and call interval are constant within a call sequence or only change gradually. However, the species can occasionally skip calls, which creates "gaps" in the sequences. The species shows shorter calls and call intervals on average than the other nyctaloid species. The serotine mainly uses fm-qcf calls. Social calls are usually only heard near the roost and should not be used to identify species; only a social call that resembles the walking stick calls of Daubenton’s bat, uttered more frequently in flight, is characteristic.

2.4.1 Overview Tab. 5 shows an overview of the measured variables of the call types as well as the possibilities of confusion, and Fig. 36 shows a typical call sequence of the serotine.

Tab. 5: Areas for different measurements of the call types of the serotine; Extreme values are given in brackets.

Call type Fc (kHz) FMk (kHz) D (ms) Confusion types Determinability qcf 21–25(26) 10–16(18) Vmur, Nlei Characteristic fm-qcf 22–31 4–16(18) Vmur, Nlei, Nnoc, Enil Characteristic under 26 kHz fm (25)26–34 3–7 Vmur, Nlei, Nnoc, Enil not determinable

Fig. 36: Typical sequence of the serotine with fm-qcf calls; the call intervals are shown shortened.

2.4.2 Location calls The qcf calls of the serotine that are used without frequency changes always show a frequency drop of 5 to 10 kHz over the entire course of the call (Fig. 37). The call intervals between qcf calls are relatively constant at around 300 ms. The qcf calls of the northern bat have a similar shape (see Fig. 42), but mostly both flatter and longer and can be easily distinguished from those of the serotine due to their higher frequency of over 25 kHz. The parti-coloured bat and the noctule can be distinguished because they usually have longer and more irregular call intervals and the longer calls of these species are almost constant frequency.

Bayerisches Landesamt für Umwelt 2020 41 Identification Criteria for Species and Groups

Fig. 37: Selection of different qcf calls from the serotine fm-qcf calls of the serotine (Fig. 38) are difficult to separate from pure fm calls, since they only become a constant frequency a short distance before the end and usually show a small tick immediately afterwards. This hook is almost always easy to recognize and relevant for identification, since it occurs only sporadically and less pronounced in other species.

The fm-qcf calls are in the frequency range of various other types. Compared to Leisler’s and parti- coloured bats, however, the calls show a weak knee. They are usually bent evenly. The northern bat uses similar calls, but most of them are higher in frequency. Below 26 kHz they are certainly serotine calls. Pure fm calls (Fig. 39) rarely occur and cannot be identified.

Fig. 38: Selection of different fm-qcf calls from the serotine. The second, third and fourth call from the right shows a clear uppercut at the end of the call.

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Fig. 39: Selection of different fm calls from the serotine

2.4.3 Social calls The serotine rarely makes social calls in the habitat. Only the subsequent call (Fig. 40), which is scattered in localization sound sequences, is relevant to identification. It is an unusually high- frequency social sound that begins with a qcf part around 60 kHz and then drops to 40 to 35 kHz. The length is approximately 20 ms. The call is reminiscent of the high calls of the barbastelle and the so-called walking stick calls of Daubenton’s bat, which are, however, much shorter.

The serotine makes a number of other social calls, which should not, however, be used to identify the species. They can be found in Fig. 92 to Fig. 94 in the appendix.

Fig. 40: Two social calls of the serotine, similar to the walking stick calls of Daubenton’s bat. More calls see Fig. 91 in the appendix.

Bayerisches Landesamt für Umwelt 2020 43 Identification Criteria for Species and Groups

2.4.4 Distinctive calls Call sequences with fm-qcf and qcf calls can be identified if there are no call changes and the calls are very uniform in terms of shape, frequency and call interval. For qcf calls, the call intervals must be approximately 300 ms (200–400 ms) and for fm-qcf calls between 100 and 300 ms. In the case of the latter, the upward ticks at the end of the call must be pronounced. The lowest frequencies of the calls must be between 21 and 25 kHz for qcf calls and must not exceed 26 kHz for fm-qcf calls.

2.4.5 Criteria for verification of species • There must be at least three sequences with distinctive location calls (more than 20 calls together) and no confusion types may occur in close proximity (+/- 2 minutes).

• Social calls: a sequence with at least one social call. Locating calls must also be present in the sequence, which at least do not speak against the species.

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2.5 The Northern Bat - Eptesicus nilssonii Degree of difficulty according to Tab. 1: Expert I (***).

2.5.1 Overview The northern bat uses higher frequency ranges than the other nyctaloid species and is usually easy to distinguish from them. Their calls are almost in the frequency range of Savi's pipistrelle and the pond bat. The shape and rhythm of the different call types of the northern bat are similar to those of the serotine. Like this, the northern bat shows no frequency change in the sequences. The call rate is high and regular. The northern bat uses qcf calls more often than the serotine. The majority of qcf and fm-qcf calls can be identified. Arched social calls are uttered in flight, which can be identified in the typical form.

2.5.2 Location calls Tab. 6 shows an overview of the measurements of the call types as well as the possibility of confusion, and a typical call sequence of the northern bat is shown in Fig. 41.

Tab. 6: Areas for different measurements of the call types of the northern bat; Extreme values are given in brackets.

Call type Fc (kHz) FMk (kHz) D (ms) Confusion types Determinability qcf (25)26–30 10–22(25) Nlei, Vmur, Eser characteristic fm-qcf 26–33 4(5)–19 Nlei, Vmur, Eser characteristic fm 26–35 3–7 Nlei, Vmur, Eser not determinable

Fig. 41: Typical sequence of the northern bat with relatively flat fm-qcf calls; the call intervals are shown shortened.

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The qcf calls of the northern bat are often longer (sometimes > 20 ms) and flatter than those of the wide-wing bat. The characteristic frequency is usually 27 to 28 kHz (Fig. 42) and the intervals 200 to 400 ms. Such calls are unmistakable. However, sometimes the calls reach almost 25 kHz. These calls are hardly distinguishable from those of the serotine, but also from those of the noctule and the parti-coloured bat.

Fig. 42: Selection of different qcf calls from the northern bat

Sequences with fm-qcf calls can also be recognized by the high characteristic frequencies (Fig. 43). They are often around 30 kHz. The other types only reach the 30 kHz limit with very short calls (<6ms). Longer fm-qcf calls from the northern bat can also have relatively low frequencies, well below 30 kHz. Then the sequences on the uniform calls and call intervals (call intervals are between 100 and 300 ms) can be distinguished from those of noctules and parti-coloured bats. The serotine can be excluded by using lower frequencies. However, there is an overlap of the two related species, which is why only calls to the northern bat should be assigned that have a length of at least 10 ms and a characteristic frequency of 28 kHz and higher. Pure fm calls (Fig. 44) are short and cannot be distinguished from those of other nyctaloid species.

Fig. 43: Selection of different fm-qcf calls from the northern bat

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Fig. 44: Selection of different fm calls from the northern bat

2.5.3 Social calls Different types of "location-call-like" to "arched" calls can be recorded more often of this species, which are made both in the habitat and near the roost. In their most common form, they are relatively uniform and easy to identify (Fig. 45). These were interpreted by Skiba (2009) as contact calls. Bow calls are emitted on the fly in autumn and are often interspersed individually, or in small groups, between location calls, but can also be made regularly at longer intervals without location calls. They are relatively short (6–20 ms) and end deep at around 10–15 (20) kHz. Their start frequency is relatively low (at 30–40 kHz) and the bandwidth is therefore small.

Many species can make similar bow calls. However, noctules never express such calls in isolation, but always in conjunction with various other social calls. The barbastelle and the long-eared species show similar bow calls, but can usually be differentiated with certainty (Fig. 46): The starting frequency of the bow calls of the long-eared bats is higher (around 60 kHz) than that of the northern bat, has been bent several times and they are usually missing a clear qcf ending. The barbastelle, on the other hand, uses calls with a smaller bandwidth and a slightly higher characteristic frequency (Fc around 20 kHz). They are also more linear, bowl-shaped or wavy in shape.

Fig. 45: Selection of different "call similar" to "arched" social calls of the northern bat. Further call variants see Fig. 95 in the appendix.

Bayerisches Landesamt für Umwelt 2020 47 Identification Criteria for Species and Groups

Fig. 46: Typical bow calls of the long-eared bats, the northern bat and the pug bat

In addition to the typical bow calls, the northern bat also uses somewhat higher-frequency and mostly shorter calls similar to location calls. They can also drop linearly without an arc (see appendix). There are also trills that can be uttered in flight like the bow calls (see Fig. 96 in the Appendix). Additional social noises can be recorded around and in roosts, but have not been sufficiently investigated. Only the lower bow calls (Fig. 46) are characteristic and can be identified (by experts). All other social noises should not be used for the identification.

2.5.4 Distinctive calls qcf calls can be identified if there are no call changes and the lowest frequencies are above 27 kHz. Call sequences with fm-qcf calls can be identified if they are at least 6 ms long and the characteristic frequency is not below 30 kHz.

For sequences with lower fm-qcf calls, calls over 10 ms in length and with characteristic frequencies of 28 kHz and higher can be identified. These sequences have to be very uniform in terms of shape, frequency and call interval and the call intervals have to be between 100 and 300 ms on average. Social calls can be identified if there are several stereotyped bow calls that do not start above 40 kHz and drop to 10 to 15 kHz. Other social calls can only be reliably identified with extensive expert knowledge.

2.5.5 Criteria for verification of species • A sequence with at least three qcf calls

• At least three sequences with distinctive fm-qcf calls (together> 20 calls); no confusion in close proximity (+/- 2 minutes)

• A recording with at least three typical social calls (bow calls) and suitable location calls in the call sequence; no confusion in close proximity (+/- 2 min)

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2.6 Savi’s pipistrelle - Hypsugo savii Degree of difficulty according to Tab. 1: Expert I (***). 2.6.1 Overview

Savi’s pipistrelle is showing a tendency to spread towards the north. The number of individual finds and call recordings, especially in the Alpine foothills, is increasing. However, no reliable statements can currently be made about a fixed settlement area.

Savi’s pipistrelle mainly uses qcf and fm-qcf calls, which are in the frequency range between those of the northern bat and the deep-calling Pipistrellus species. However, there is an overlap with Nathusius’ and Kuhl’s pipistrelles, especially for shorter calls. The pond bat calls in the same frequency range, but its calls are modulated differently. In terms of shape, call length and call spacing, the location calls are very similar to those of the Pipistrellus species. The calls of Savi’s pipistrelle are somewhat longer on average. The call rhythm is more regular and the intervals are longer. The social calls of the species are probably characteristic, but so far the data situation in Central Europe has not been sufficient for an assessment. Courtship trills such as those used by the Pipistrellus species are not (yet?) known from Savi’s pipistrelle.

2.6.2 Location calls Tab. 7 shows an overview of the measurements of the call types as well as the possibility of confusion, and Fig. 47 shows a typical and easily identifiable call sequence of Savi’s pipistrelle.

Tab. 7: Areas for different measurements of the call types as well as confusion possibilities of Savi’s pipistrelle; Extreme values are given in brackets.

Call type Fc (kHz) FMk (kHz) D (ms) Confusion types Determinability qcf (30)31–35(36) 8–15(17) Pkuh, Pnat, Mdas characteristic fm-qcf 31–38(42) (4)5–14 Pkuh, Pnat, Mdas characteristic fm 34–41 3–5(7) Pkuh, Pnat, Mdas not determinable

Fig. 47: Typical sequence of Savi’s pipistrelle with qcf and fm-qcf calls; the call intervals are shown shortened.

The species often uses qcf calls, the characteristic frequency of which is between 31 and 35 kHz (in exceptional cases also 36 kHz) (Fig. 48). There is no overlap with the northern bat, since its qcf calls only reach a maximum of 30 kHz. However, there is an overlap area with Kuhl’s and Nathusius’ pipistrelles. In extreme cases, these can make calls just below 35 kHz, which is why only qcf calls up to 34 kHz can be safely attributed to Savi’s pipistrelle.

Bayerisches Landesamt für Umwelt 2020 49 Identification Criteria for Species and Groups

Fig. 48: Selection of different qcf calls from Savi’s pipistrelle

It is even more difficult to distinguish between fm-qcf calls (Fig. 49). A good indication can be given by the shape of the calls, which is usually quite characteristic in Savi’s pipistrelle. fm-qcf calls almost always have a very clear knee. The following qcf part is not curved, but either constant frequency or slightly linearly falling. The introductory fm part of the calls can have several conspicuous knees. Nathusius’ and Kuhl’s pipistrelles, on the other hand, show a rather evenly rounded transition between the fm and qcf parts. However, the variability is high in all three types, so that this is not a sure differentiation criterion. As fairly certain, only fm-qcf calls with a characteristic frequency below 35 kHz can be assigned to Savi’s pipistrelle.

Fig. 49: fm-qcf calls of Savi’s pipistrelle

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Savi’s pipistrelle quite often uses fm-calls in localization (Fig. 50). These calls also show a clear knee.

Fig. 50: Selection of different fm calls from Savi’s pipistrelle

Calls of the pond bat can also be confused with fm and fm-qcf calls of Savi’s pipistrelle, since the "myotis-knick" and the characteristic frequency are in similar ranges. A distinction is possible, however, if the shape of the calls is observed. The calls of the pond bat are much more frequency- modulated than the similarly short calls of Savi’s pipistrelle. In addition, the knee is not sharply pronounced in pond bat calls, and is not followed by a longer linear section, but a smooth transition from the fm part to the flatter end part. Only very long calls from the pond bat (= 12 ms in length) have a longer qcf ending. However, these calls are not consistently flat, but at least at the beginning show a clear drop in frequency. Extremely long calls from the pond bat (about 20 ms) can exceptionally be pronounced as real qcf calls. In this case, qcf calls from Savi’s pipistrelle can be excluded, since they are only 17 ms long.

A problem in the identification of location calls with an Fc <34 or 35 kHz are new observations, according to which males of Kuhl’s pipistrelle can apparently shift the frequency of their location calls down by about 5 kHz during courtship. As a result, the calls are in the frequency range of Savi’s pipistrelle (see Fig. 56). However, the shape of these calls differs significantly from that of Savi’s pipistrelle (for a distinction see the chapter on Kuhl’s pipistrelle). The typical courtship call of Kuhl’s pipistrelle is often present in such sequences. To be on the safe side, questionable sequences during the courtship period (August – September) should be checked by an expert.

2.6.3 Social calls As far as we know, no safe social sounds of the species have been recorded in Germany. Barataud (2015) and Nardone et al. (2017) describe calls that are uttered on the fly in the habitat. They are mainly complex songs consisting of several syllables. The call types involved can be arc calls, location-like signals and/or wave-like calls. The latter are the most characteristic and quite long (12– 55 ms). Their main frequency is usually between 20 and 30 kHz. These calls can probably be identified with certainty. However, since we have no comparable calls so far, we cannot include them in these criteria.

Bayerisches Landesamt für Umwelt 2020 51 Identification Criteria for Species and Groups

Short trills, such as those often used by Pipistrellus species for courtship and territory delimitation, are not yet known from Savi’s pipistrelle. However, Nardone et al. (2017) see evidence that Savi’s pipistrelle can use similar trills.

2.6.4 Distinctive call types Qcf calls can be identified if the lowest characteristic frequencies do not exceed 34 kHz. Call sequences with fm-qcf calls can be identified if the characteristic frequency is not above 35 kHz.

2.6.5 Criteria for verification of species • At least three sequences with distinctive qcf or fm-qcf calls (together> 20 calls); no confusion in close proximity (+/- 2 minutes).

• No social calls from Kuhl’s pipistrelle may occur at the location. Pay attention to the characteristic shape of the calls of Savi’s pipistrelle (the sharp knee and the characteristic frequency of the call must not be more than 5 kHz apart).

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2.7 Kuhl’s and Nathusius’ Pipstrelles - Pipistrellus kuhlii and P. nathusii Difficulty level according to Tab. 1: Layman II (**).

2.7.1 Overview The call repertoire of the Kuhl’s pipistrelle almost completely overlaps with that of Nathusius’ pipistrelle. Both species occur syntopically throughout the year in suitable habitats in southern Germany. Therefore, these two types are treated together in this guide. Kuhl’s pipistrelle tends to use qcf calls less often and more often uses lower fm-qcf calls than Nathusius’ pipistrelle. However, courtship calls are species-specific.

Kuhl’s pipistrelle is a bat species that has probably migrated to southern Germany as part of climate change. It was first proven in Bavaria in Munich in 1996. In the meantime she frequently appears in the Munich-Dachau area and in Augsburg. Reproduction has also been demonstrated in recent years on the Danube (Neu-Ulm, Ingolstadt) and in Southeast Bavaria (Rosenheim). In the meantime, an occurrence in Aschaffenburg in the extreme north-west of Bavaria has also been proven on the basis of records of clearly identifiable social calls.

2.7.2 Location calls Table 8 shows an overview of the measured variables of the call types as well as the possibility of confusion, and Fig. 51 shows a typical and easily definable call sequence of Nathusius’ pipistrelle.

Tab. 8: Areas for different measurements of the call types of Kuhl’s and Nathusius’ pipistrelle; Extreme values are given in brackets.

Call type Fc (kHz) FMk (kHz) D (ms) Confusion types Determinability 5– Hsav, Ppip qcf (34)35–41(42) characteristic 10(12) fm-qcf 35–45 (3)4–11 Hsav, Ppip characteristic fm 36–46 3–5(6) Hsav, Ppip not determinable

Fig. 51: Typical sequence of Nathusius’ pipistrelle with qcf and fm-qcf calls; the call intervals are shown shortened.

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The longest and deepest qcf calls (Fig. 52) of Kuhl’s and Nathusius’ pipistrelle can be up to 12 ms long and their characteristic frequency is just under 35 kHz; there is then an overlap with the Savi’s pipistrelle. The highest characteristic frequencies for this type of call are 41 (Kuhl’s) and 42 kHz (Nathusius’). There is an overlap with the common pipistrelle, the lowest calls of which are just over 40 kHz. Only qcf calls between 36 and 40 kHz can be safely assigned to the species pair of Kuhl’s and Nathusius’ pipistrelle.

Fig. 52: Selection of different qcf calls from Kuhl’s / Nathusius’ pipistrelle

The fm-qcf calls (Fig. 53) show large overlaps in the frequency range with those of Savi’s and the common pipistrelle bat. Only calls that are at least 7 ms long and whose characteristic frequency is between 37 and 40 kHz can be reliably identified. Shorter calls cannot be identified. The calls of Savi’s pipstrelle are often shaped significantly differently with the sharper knee and the sometimes additionally kneeled fm part, while the transition between the fm and qcf part is more gently rounded for Kuhl’s and Nathusius’ pipistrelle. However, deviations from the norm occur on both sides, so that these characteristics are only a guide.

Fig. 53: Selection of different fm-qcf calls from Kuhl’s / Nathusius’ pipstrelle

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Fm calls (Fig. 54) are rarely used by Kuhl’s and Nathusius’ pipistrelles in localization. Usually there are only very few calls in a sequence. They are not relevant to identification.

Fig. 54: Selection of different fm calls from Kuhl’s / Nathusius’ pipistrelle

A phenomenon that has only recently been recognized is location calls of Kuhl’s pipistrelles during courtship. During mating flights, the males can emit location calls that are a few kHz lower than usual (Fig. 55). These calls are then in the frequency range of the Savi’s pipistrelle and the pond bat (30-36 kHz). Sometimes only single deeper calls are used in the sequences (Fig. 56); however, some animals utter these calls throughout. These are fm and fm-qcf calls, which have only a weak knee and whose rear part of the call can only have a short qcf portion at the very end. They show a clear "myotis tail", which is why calls are more likely to be confused with species of the genus Myotis (e.g. pond bat) than with Savi’s pipistrelle. The typical courtship call of Kuhl’s pipistrelle is almost always present in such sequences.

Not enough is known about the phenomenon to be able to give more precise recommendations in these criteria. To be on the safe side, questionable sequences during courtship (mainly August to September) should be checked by an expert.

Fig. 55: Deep fm and fm-qcf calls of a male Kuhl’s pipistrelle during courtship; the call intervals are shown shortened.

Bayerisches Landesamt für Umwelt 2020 55 Identification Criteria for Species and Groups

Fig. 56: A male Kuhl’s pipistrelle changes from deep calls to normal location calls (about 8 kHz difference) during the courtship period; the call intervals are shown shortened.

2.7.3 Social calls Kuhl’s and Nathusius’ pipistrelles can be differentiated based on their characteristic social calls. Nathusius’ pipistrelle expresses a trill as a courtship call mainly in summer and autumn. This complex call consists of two trills and an intermediate call (Fig. 57). In this form it is unique among the Pipistrellus species. The first trill resembles that of the common pipistrelle. However, the hook- shaped elements (5–8) usually extend somewhat lower in frequency, up to around 14 kHz. The middle element of the call, the "intermediate call", is a short fm sound that ends at 20 to 30 kHz and is similar to the location calls of the genus Myotis. The final trill consists of several U-shaped elements. These are significantly higher in frequency than those of the first trill (30–70 kHz). The shape of the rear trill is extremely variable. Often only partial elements of the call complex are used. The middle fm call is not always recognizable, may be missing or can be made in isolation.

Fig. 57: Typical courtship call of Nathusius’ pipistrelle consisting of two trills and a middle fm element. Further courtship calls see Fig. 97 in the appendix.

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Kuhl’s pipistrelle only uses simple trills, which usually consist of two to four elements (Fig. 58). These show an fm-qcf shape. The lowest frequency of the elements is 12 to 14 kHz. The courtship calls are lower than that of all other Pipistrellus species. The front elements are also longer (max. 7– 12 ms) than with other types. The individual syllables can be connected in waves.

Fig. 58: Typical courtship trill of Kuhl’s pipistrelle. More courtship trills see Fig. 98 in the appendix

Kuhl’s pipistrelle also shows bow calls in the habitat (Fig. 59). These are on average over 10 ms long and end at around 23 to 25 kHz. The call is relatively variable and can resemble arcs of other types. However, if it is recorded in connection with location calls, it can be used to distinguish it from Nathusius’ pipistrelle.

Fig. 59: Typical bow call (contact call in the habitat) of Kuhl’s pipistrelle. More bow calls see Fig. 99 in the appendix.

Bayerisches Landesamt für Umwelt 2020 57 Identification Criteria for Species and Groups

2.7.4 Distinctive call types Qcf calls with a characteristic frequency above 36 to a maximum of 40 kHz can be identified. Call sequences with fm-qcf calls can be identified if the calls are at least 7 ms long and the characteristic frequency is between 37 and 40 kHz.

The courtship calls of the Kuhl’s and Nathusius’ pipistrelles are species-specific. In the Nathusius’ pipistrelle, there should be at least two of the three elements of the call complex. Sequences with bow calls from Kuhl’s pipistrelle can be used to distinguish it from the Nathusius’ if they are about 10 ms long and the frequency at the kink (FMk) is between 20 and 25 kHz 2.7.5 Criteria for verification of species • Group level: at least one sequence with distinctive qcf or fm-qcf calls (together> 5 calls).

• Species level: at least one typical courtship call or a sequence with location calls and a bow call from Kuhl’s pipistrelle.

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2.8 The Common Pipistrelle - Pipistrellus pipistrellus Difficulty level according to Tab. 1: Layman II (**).

2.8.1 Overview The common pipistrelle bat can usually be easily identified based on its qcf and fm-qcf location calls, even if there are overlaps with other Pipistrellus species. Short fm calls cannot be identified; they can be confused with calls from other Pipistrellus species and also calls from the Alcathoe bat. The courtship calls of the males are typical of the species.

2.8.2 Location calls The location calls of the common pipistrelle are in a broad frequency range from 40 to over 50 kHz; on average, the characteristic frequency is 45 to 46 kHz. The females call (as with other Pipistrellus species) a little lower than the males. This could explain why in some locations all calls of the species are difficult to separate from Kuhl’s / Nathusius’ pipistrelles and in other locations they are more similar to the calls of the soprano pipistrelle. Tab. 9 lists the measured variables of the call types as well as the possibility of confusion, and Fig. 60 shows a typical and easily definable call sequence of the common pipistrelle.

Tab. 9: Areas for different measurements of the call types of the common pipistrelle; Extreme values are given in brackets.

Call type Fc (kHz) FMk (kHz) D (ms) Confusion types Determinability qcf >40–50 5–10 (11) Pnat/Pkuh, Ppyg characteristic fm-qcf (41)42–54 3–10 Pnat/Pkuh, Ppyg characteristic fm (44)45-55 3–5(6) Pnat/Pkuh, Ppyg, Malc not determinable

Fig. 60: Typical sequence of the common pipistrelle with qcf and fm-qcf calls; the call intervals are shown shortened.

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The species often uses qcf calls with a maximum call length of 11 ms (Fig. 61). These calls can be identified if their characteristic frequency is between 43 and 50 kHz. Deeper calls cannot be distinguished from those of the pair of Kuhl’s / Nathusius’ pipistrelles.

Fig. 61: qcf calls of the common pipistrelle; the call intervals are shown shortened

Fm-qcf calls (Fig. 62) show an even greater overlap with Nathusius’ and Kuhl’s pipistrelles. Higher calls (up to max. 54 kHz) are in a range in which the soprano pipistrelle also calls. Only fm-qcf calls longer than 4 ms can be reliably identified. If such calls have a characteristic frequency above 45 kHz to a maximum of 50 kHz, they can be assigned to the common pipistrelle. If the calls are 7 ms long, they can also reach down to 43 kHz.

Fig. 62: Selection of different fm-qcf calls from the common pipistrelle

Very short calls in dense vegetation and in localization can be pronounced as fm calls (Fig. 63). These calls are not suitable for identification. They sometimes resemble the calls of the Alcathoe bat. If the calls originate from the common pipistrelle, the Alcathoe can be excluded very easily, since there are almost always fm-qcf calls in the same sequence or in other recordings shortly before or after. For a distinction, see also the chapter on the Alcathoe bat.

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Fig. 63: Selection of different fm calls from the pipistrelle bat

2.8.3 Social calls Like all Pipistrellus species, the common pipistrelle shows a short trill (Fig. 64), which is expressed both during courtship and in the hunting area (when it is interpreted as territorial behaviour). This species-specific short trill consists of several elements, which first decrease in frequency and then show a short quasi-constant frequency or rising again. The individual pulses of the two to six elements are less than 6 ms long; only the last pulse is sometimes longer. The bandwidth of the individual pulses is relatively narrow and usually not larger than 15 kHz. The lowest frequencies of the elements are between 15 and 20 kHz. This distinguishes them from trills of Kuhl’s pipistrelle, whose individual pulses are longer and broader and end between 11 and 14 kHz. The trill pulses of the soprano pipistrelle are also broadband (around 20 kHz). Their minimum frequencies are around 20 kHz. These pulses start with a downward hook.

Fig. 64: Courtship trill of the common pipistrelle bat. More courtship trills see Fig. 100 in the appendix.

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Especially in the roost, but also in the habitat, various long calls are uttered, which Pfalzer (2002) calls bow calls and Skiba (2009) calls contact calls (Fig. 65). These, sometimes complex-shaped, location-like to arc-shaped sounds are mainly used for mother-child communication. While longer, mostly somewhat wavy, calls are likely to come from the young; other calls may also represent calls from the mother animals. Here are for example the double calls mentioned by Pfalzer (2002) (Fig. 102). Their variability is large, which is why it is difficult to subdivide and describe individual types. Reliable species identification has not been possible on the basis of these calls, since the soprano pipistrelle in particular makes similar and equally variable calls. Individual forms of the call can also be confused with bow calls from other species (e.g. from the genus Nyctalus and Myotis). Since the calls are almost always recorded in the vicinity of the roost, the many location calls recorded at the same time provide important information for species identification.

Fig. 65: Different bow calls of the common pipistrelle. More bow calls see Fig. 101 &. Fig. 102 in the appendix.

2.8.4 Distinctive call types Qcf calls with a characteristic frequency of 42 to a maximum of 50 kHz can be identified. Call sequences with fm-qcf calls can be identified if the calls are at least 4 ms long and the characteristic frequency is below 50 kHz. At the bottom, Fc must not fall below 45 or 43 kHz for calls that are 7 ms long or longer.

The courtship calls of the common pipistrelle are species-specific. The first pulse must be shorter than 5 ms, the lowest frequency must not be below 14 kHz and the frequency bandwidth of the individual pulses must be less than 16 kHz.

2.8.5 Criteria for verification of species • At least one sequence with distinctive qcf or fm-qcf calls (> 3 calls)

• At least one typical courtship call of type

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2.9 The Soprano Pipistrelle - Pipistrellus pygmaeus Degree of difficulty according to Table 1: Layman II (**).

2.9.1 Overview The soprano pipistrelle's location calls are in a broad frequency range from 50 to over 60 kHz. There is a small area of overlap with the common pipistrelle; the species in Central Europe cannot be confused with species other than the common pipistrelle. A short trill, which is mainly expressed for courtship, but also for the delimitation of territories of males, can be used to identify the species under certain conditions.

2.9.2 Location calls Tab. 10 shows an overview of the measured variables of the call types as well as the possibility of confusion, and Fig. 66 shows a typical and easily definable call sequence of the soprano pipistrelle.

Tab. 10: Areas for different measurements of the call types of the soprano pipistrelle; Extreme values are given in brackets

Call type Fc (kHz) FMk (kHz) D (ms) Confusion types Determinability qcf (49)50–56 (60) (4)5–8(10) Ppip characteristic fm-qcf (50)51–64 (68) 3–10 Ppip characteristic fm 56–68 3–5(7) Ppip not determinable

Fig. 66: Typical sequence of the soprano pipistrelle with qcf and fm-qcf calls; the call intervals are shown shortened. qcf sounds of the soprano pipistrelle (Fig. 67) are usually no longer than 8 ms (in exceptional cases up to 10 ms). The characteristic frequency of these calls is between 50 and 60 kHz. For calls with a length of more than 4 ms, Fc must be above 51 kHz in order to clearly distinguish them from the common pipistrelle. There are areas in Europe (e.g. England, own observations) in which the characteristic frequency of the qcf calls can be below 50 kHz. However, this is not the case in Central Europe.

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Fig. 67: Selection of different qcf calls from the soprano pipistrelle

The characteristic frequency of the fm-qcf calls (Fig. 68) can rise significantly above 60 kHz. Calls of less than 5 ms in length are often pronounced as pure fm calls (Fig. 69). There is a certain risk of confusion with calls from the Alcathoe bat, but the kink is not above 55 kHz.

Since short calls of the common pipistrelle can also have characteristic frequencies up to 55 kHz, fm-qcf calls of the soprano pipistrelle up to 4 ms in length may only be identified if their Fc is above

55 kHz. With longer fm-qcf calls, the Fc must be above 53 kHz. Pure fm sounds should not be used for identification.

Fig. 68: Selection of different fm-qcf calls from the soprano pipistrelle

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Fig. 69: Selection of different fm calls from the soprano pipistrelle

2.9.3 Social calls The soprano pipistrelle often expresses a species-specific short trill, which is expressed during courtship, but also in the hunting area (then interpreted as territorial behaviour) (Fig. 70). It consists of several elements that first decrease in frequency and then show a quasi-constant frequency or ascending pattern. The individual pulses of the two to five pulses are similar to those of the common pipistrelle; however, their bandwidth is larger (> 15 kHz). The lowest frequencies of the elements are around 20 kHz and thus higher than those of the common and Kuhl’s pipistrelles. In addition, a clear downward hook is formed at the beginning of the individual pulses.

Fig. 70: Typical courtship trill of the soprano pipistrelle. More courtship trills see Fig. 103 in the appendix.

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Especially in the roost, but also in the habitat, various long calls are uttered, which Pfalzer (2002) calls bow calls and SKIBA (2009) calls contactcalls (Fig. 71). These, sometimes complex-shaped location-call-like to arch-shaped calls probably also serve for mother-child communication in the soprano pipistrelle. They resemble the bow calls of the common pipistrelle bat. In addition to longer bow calls, there are also double calls for the soprano pipistrelle (see Fig. 105 in the Appendix). The variability of the location-like to arc-shaped sounds is so great that it is difficult to subdivide and describe individual types of calls precisely.

Fig. 71: Different bow calls from the soprano pipistrelle. More bow calls see Fig. 104 & 105 in the appendix.

The social calls of the soprano pipistrelle tend to be somewhat higher-frequency and shorter than that of the common pipistrelle. The bow calls of the soprano pipistrelle usually also increase significantly in frequency at the end. Individual forms of the calls can also be confused with bow calls from other species (e.g. the genres Nyctalus and Myotis). Since the calls are almost always recorded near the roost, the many location calls recorded at the same time provide important information about the originators. So far, however, it has not been possible to reliably identify the species based on the call-like to arch-shaped sounds.

2.9.4 Distinctive call types qcf calls can be identified with a characteristic frequency above 51 kHz. fm-qcf calls under 4 ms in length can be identified with a characteristic frequency of more than 55 kHz and from 4 ms in length with an Fc over 53 kHz.

The courtship calls of the soprano pipistrelle are species-specific if the lowest frequency is above 16 kHz, the frequency bandwidth of the individual pulses is greater than 16 kHz and there is a clear tick at the beginning of the elements.

2.9.5 Criteria for verification of species • At least one sequence with distinctive qcf or fm-qcf calls (> 3 calls)

• At least one typical type of courtship call

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2.10 The Brown and the Grey Long-eared Bat – Plecotus auritus and P. austriacus Degree of difficulty according to Tab. 1: Expert I (***).

2.10.1 Overview Brown and grey long-eared ears use very similar location calls and are therefore not differentiated in this guide. Grey long-eareds tend to call in more open habitats and then use longer and louder calls. Both types use quiet and rather short fm sounds. Compared to the sounds of the Myotis species, the calls are usually low-frequency, have a narrower range and are shaped differently. The first overtone is often strikingly loud. Typical location calls of these types can be easily identified. The social calls (bow calls) made in flight can usually also be identified at the generic level. So far it has not been adequately investigated whether social calls can be used to distinguish between these two types in Central Europe. The measured variables of the calls as well as the possibilities of confusion are listed in Table 11 for an overview. Fig. 72 shows a typical call sequence of the long-eareds, Figures 73 to 75 show typical and easily identifiable calls with different call lengths.

Tab. 11: Areas for different measurements of the calls of the long-eareds; Extreme values are given in brackets.

Call type Fc (kHz) FMk (kHz) D (ms) Confusion types Determinability fm 35–60; mostly (11)20–35 2–8 Bbar, nyctaloid characteristic at around 40 approach calls

Fig. 72: Typical sequence of brown / grey long-eareds; the call intervals are shown shortened.

2.10.2 Location calls Long-eared calls are 2 and 8 ms long fm-calls with a stressed second harmonic (1st overtone), which is often as loud as the fundamental frequency. The species call in a low frequency range and show only a small bandwidth of mostly just over 20 kHz. These features together with a unique form of the calls allow the clear distinction between fm calls from the genus Myotis. In addition to a clear knee, the calls also show a "Myotis-knick" followed by a tail. This often ends in a qcf part, leading to a stair- like sonagram. Regardless of the length of the calls, the start frequency can be between 35 and 60 kHz, but usually 40 kHz.

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The frequency at the “Myotis-knick” increases significantly with shorter calls. For very short calls, FMk can be between 25 and 35 kHz. For longer calls, the value is between 20 and 25 kHz. Sometimes location calls occur that are extremely low (FMk minimum at 11 kHz; see Fig. 75 second call from the left). It is unclear whether such calls already have a social component.

Very short calls of the long-eared bats (Fig. 73) usually have no characteristic frequency modulation and can be confused with very short local calls and swarming sounds of nyctaloid species. These differ, however, in that they are usually embedded in sequences with calls and call intervals of different lengths, while the call sequence for long-eared ears is quite uniform (call intervals usually 100–300 ms). In swarming Nyctalus species, social calls can also often be found. The short and deep call type of the barbastelle also resembles short calls of the long-eareds, since it lies in a similar frequency range and usually also has strong harmonic frequencies. However, the frequency bandwidth is smaller than with long-eareds. In addition, the barbastelle generally uses two calls of different frequency and shape. Local calls of the barbastelle, however, do not show this frequency change and are also broadband. However, these calls have shorter call intervals of only about 30 ms.

Fig. 73: Selection of different short calls from brown / grey long-eared bats (<4 ms); A sonagram with an FFT overlap of 93.75% for comparing location calls of different lengths within the long-eareds can be found in the appendix (Fig. 106).

Fig. 74: Selection of different medium-long calls from brown / grey long-eared bats (4–6 ms).

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Fig. 75: Selection of different long calls from brown / grey long-eared bats (6–8 ms).

2.10.3 Social calls The most common expression of the long ears in a social context is a low fm call or bow call (Fig. 76). It is relatively uniform and can be recorded at summer and winter roosts as well as in the habitat. This call is generally interpreted as a courtship call, which is also used territorially in the hunting area. The call usually begins at just over 50 kHz (50–60 kHz) and ends in a short qcf part at around 14 kHz. It often has one or more knees and is usually 10 ms long. The courtship calls of the grey long-eared bat probably have slightly lower start frequencies than those of the brown long-eared bat. However, this has not yet been sufficiently investigated for Central Europe.

These bow calls are either made alone in longer sequences with call intervals between 200 to 300 ms or as short pulse sequences (pulse intervals around 35 ms) between location calls. The calls can resemble short bow calls of other types. The genus Nyctalus and the northern bat are particularly worth mentioning here. However, Nyctalus species rarely use short and deep bow calls. These are always framed in various other social and location calls, especially when swarming, and are never uttered at regular intervals alone. This also applies to the social calls of the northern bat, which can be as long and uniform as that of the long-eared bat. With these calls, however, either the frequency in the flat end part is higher (around 20 kHz) or the start frequency is significantly below 50 kHz.

Other types of social calls are used in roosts (trills, wave-shaped and hook-shaped elements, about whose determinability no statements can currently be made).

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Fig. 76: Different bow calls from brown / grey long-eared bats. More calls see Fig. 107 in the appendix.

2.10.4 Distinctive call types Fm location sounds can be identified if there is a longer call sequence with uniform calls and regular call intervals. Social calls are also characteristic if there is a series of uniform calls with end frequencies around 14 kHz (13–15) and start frequencies not below 50 kHz, possibly accompanied by location sounds.

2.10.5 Criteria for verification of species • At least one sequence with distinctive fm calls (> 3 calls) and no confusion in close proximity (+/- 2 minutes).

• At least one sequence with distinctive courtship calls (> 3 calls) and no confusion in close proximity (+/- 2 minutes). No locating sounds of other species may be included in the sequence (pay particular attention to nyctaloid species).

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2.11 The Barbastelle - Barbastella barbastellus Difficulty level according to Tab. 1: Layman I (*).

2.11.1 Overview For normal location, the barbastelle uses two types of calls, which are emitted alternately. These call types differ in length, frequency range and frequency modulation. Such sequences, but also the individual calls, are unmistakable. Even the rather monotonous social calls (bow calls) can be easily identified if there are several. Table 12 shows an overview of the measured variables of the call types and the possibilities of confusion. Fig. 77 shows a typical and easily definable call sequence with alternating call types.

Tab. 12: Areas for different measurements of the calls of the pug bat; Extreme values are given in brackets

Call type Fc (kHz) FMk (kHz) D (ms) Confusion types Determinability Type A 33–36(39) (27)30–32 <2–3,5(5) characteristic Type B (40)43–46(50) (29)30–35(37) 2–6(10) Mdau (social) characteristic Localization Partly Localization (42)46–55 (20)25–30 2–5(6) nyctaloid, characteristic Plecotus

Fig. 77: Typical sequence of the barbastelle with alternating call types A and B; the call intervals are shown shortened.

2.11.2 Location calls The lower call type A (Fig. 78) is a short fm sound (2–5 ms) that is emitted through the mouth, which usually starts at 36 kHz and falls over a narrow frequency range of about 5 to 10 kHz. It is unmistakable due to its brevity and narrow bandwidth. The higher call type B (Fig. 79) starts around 45 kHz, is longer (up to 10 ms) than call type A and can initially show a qcf part. At the end, the call always drops sharply with frequency modulation. Since it is directed upwards by the animal and expelled through the nose (Seibert et al. 2015), call type B is usually recorded more quietly from the ground and is sometimes no longer recognizable in the recording. This type of call cannot be confused with location calls from other Central European species. However, social calls of different types can be frequency modulated similarly. Here, the "walking stick" calls of Daubenton’s bat are particularly worth mentioning. These vary widely and, in exceptional cases, can also be in a similar frequency range.

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The call type B of the barbastelle differs from them in that in the beginning it never shows a part that increases in frequency. In addition, it will never be used for a long time without the A type call.

Fig. 78: Selection of different fm calls from the barbastelle (call type A).

Fig. 79: Selection of different fm to qcf-fm calls from the barbastelle (call type B).

In the case of localization (Fig. 80), the alternating call types change into a fairly uniform, broadband fm call, which tends to be reminiscent of call type B, but can also simply drop off linearly. These calls are emitted at a high call rate (30 to 50 ms call interval). They are more difficult to identify because short swarm sounds, feeding buzz sequences and trill-like social sounds of different types can look similar. However, localization sequences of the barbastelle usually show somewhat longer calls, which are already strongly based on call type B and can then be clearly identified. Sequences that only consist of very short (<2.5 ms) and non-specific local calls should not be identified. Such sequences can be observed almost exclusively, especially in roosts or directly at the entrance (caves, tunnels, attics). In such situations, many species (e.g. genus Eptesicus or Plecotus) use extremely short and unspecific calls in the same frequency range.

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Fig. 80: Selection of different short fm calls from the barbastelle (localization)

2.11.3 Social calls The most common expression in the social context is a longer (5–45 ms), only slightly modulated call that ends around 20 kHz. This social call (Fig. 81), which resembles a bow call, is usually recorded in the vicinity of roosts and is at least partially emitted by flying animals as longer call series without further location calls. It is relatively variable: shorter calls can drop linearly in frequency, while longer calls are either arc-like or quasi-constant. Sometimes the frequency increases slightly towards the end and then drops again. Nevertheless, this call is mostly characteristic due to its length, the frequency range around 20 kHz and the low bandwidth.

At first glance, very flat calls of this type can be reminiscent of qcf location calls from nyctaloid species. The form of social calls within a sequence is almost always variable, and unusual frequency modulations also occur, which are not observed in locating calls of nyctaloid species. Another difference is that the social calls of the barbastelle have a strong 2nd harmonic, which is sometimes as loud as the fundamental vibration. In addition, the calls start very abruptly at full volume and then become quieter, so that sometimes the end is no longer clearly recognizable. Even if some bow calls of the noctule resemble the bow calls-like social calls of the barbastelle, they never appear as longer calls and are always present alongside other social or location sounds. The courtship call of Leisler’s bats ends at lower frequencies (around 13 kHz).

Fig. 81: Frequent bow-like social calls from the barbastelle. More calls see Fig. 108 in the appendix

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In summer and winter roosts in particular, other social calls of the type occur (e.g. trills or other complex social sounds). An example is “chirping” sequences at the nursery (Fig. 82). These call series consist mostly of very short, very different types of elements that follow one another closely. Bow calls are also interspersed, e.g. may resemble those of the common pipistrelle. Most of the individual elements cannot be identified and resemble call types of different types. Sometimes local calls and type B calls are interspersed, which then allow an identificaton. This social call probably corresponds to call type C, which Middleton et al. (2014) describe for the species in England. Barataud (1996) specifies a low-frequency double call as another type of call, which is to serve as area delimitation and courtship. In Germany, however, we have not yet been able to establish this reputation with certainty. In winter roosts, similar but very variable bow calls are recorded. However, these have so far been insufficiently examined and will not be dealt with further here.

Fig. 82: "Chirping" social call sequence of a barbastelle on a roost excursion; FFT overlap 87.5%.

2.11.4 Distinctive call types All locating call sequences in which the two call types A and B occur alternately can be identified.

Local calls can be identified if there are longer calls (> 3 ms) that already have the convexly curved form of call type B.

The barbastelle's bow-call-like social calls can be identified if they do not begin above 30 kHz, end around 20 kHz (18-23) and have a strong 2nd harmonic. They must exist as a call series with several calls and regular call intervals (60–300 ms).

2.11.5 Criteria for verification of species • At least one sequence with distinctive location sounds (call types A and B)

• At least one sequence with distinctive localization sounds (at least 5 calls) and no confusion in close proximity (+/- 2 minutes)

• At least one sequence with distinctive social calls (> 3 calls) and no confusion in close proximity (+/- 2 minutes). The sequence must not contain any location or social sounds from other species (pay particular attention to nyctaloid species).

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2.12 The Greater Horseshoe Bat - Rhinolophus ferrumequinum Difficulty level according to Tab. 1: Layman I (*).

2.12.1 Overview In contrast to representatives of the smooth-noses (Vespertilionidae), horseshoe bats locate only through their nose attachment instead of through the wide-open mouth. They also suppress the fundamental and emphasize the first overtone (2nd harmonic). The long, high-frequency calls of the species are unmistakable in Central Europe. The lower calls of the greater horseshoe bat are well separated from the higher frequency calls of the Lesser Horseshoe Bat. Social calls relevant to identification are not known.

2.12.2 Location calls The location calls of the horseshoe bats differ from those of all other European species by a very long, high-frequency cf part. Table 13 shows an overview of the measurements of the calls and Fig. 83 shows a typical call sequence of the greater horseshoe bat.

Tab. 13: Areas for different measurements of the calls of the greater horseshoe bat; Extreme values are given in brackets

Call type Fc (kHz) FMin (kHz) D (ms) Confusion types Determinability Fm-cf-fm (77)78–83(86) 50–78 (16)30–60(75) characteristic

Fig. 83: Typical sequence of the greater horseshoe bat; the call intervals are shown shortened. FFT overlap 87.5%.

The location calls of the greater horseshoe bat are characterized by a long high-frequency cf section around 80 kHz, which is bordered at the beginning and end by a steeply upward and downward fm section. These ups and downs are not always easy to see on quiet calls. The loudest frequency of the call is in the 2nd harmonic, while the fundamental (1st harmonic) is usually only weak and is therefore sometimes not visible. The average call length is 50 ms. However, it can vary considerably.

2.12.3 Social calls The species expresses a variety of social calls, but these are almost only heard in the roosts. In addition to noisy distress calls, there are mainly sounds that mostly represent a variation of the location calls and have a longer, high cf or qcf portion. However, such sounds are “bent” in different ways and are often composed of different elements (complex calls). Some of them are species- specific, but will not be dealt with here as they are not relevant for identification in the field.

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2.12.4 Distinctive call types The fm-cf-fm location sounds are unmistakable due to their characteristic frequency in the cf section. However technical devices can sometimes produce similar long and constant-frequency tones (e.g. high squeaking or electromagnetic radiation). However, such sounds do not have the typical fm parts at the beginning and end of the signal.

2.12.5 Criteria for verification of species

• At least one call of the type with Fc between 77 and 86 kHz and visible fm components at the beginning and end.

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2.13 The Lesser Horseshoe Bat - Rhinolophus hipposideros Difficulty level according to Tab. 1: Layman I (*).

2.13.1 Overview The location calls of the lesser horseshoe bat are unmistakable in Central Europe. In southern Europe, however, there are other species of the genus that can (regionally) call in a similar frequency range and are difficult to separate. Tab. 14 lists the measurements of the calls for an overview and Fig. 84 shows a typical call sequence of the lesser horseshoe bat.

Tab. 14: Areas for different measurements of the calls of the lesser horseshoe bat; Extreme values are given in brackets.

Call type Fc (kHz) FMin (kHz) D (ms) Confusion types Determinability Fm-cf-fm (100)105–114(116) 83–10 (16)20–60(75) characteristic

Fig. 84: Typical sequence of the lesser horseshoe bat; the call intervals are shown shortened; FFT overlap 87.5%.

2.13.2 Location calls The location calls are characterized by a cf part, which is framed by fm ups and downs.

In terms of their shape, the location calls correspond to those of the greater horseshoe bat, but are more frequent and usually shorter, which clearly distinguishes the lesser from the greater horseshoe bat. The characteristic frequency is between 105 and 114 kHz and the length is at least 20-30 ms, but varies considerably. Table 14 shows the extreme values that can be found in various European publications. It should be emphasized that the characteristic frequency of this species apparently varies within its European distribution area. So the species calls for example in England are relatively high frequency (107-114 kHz). In Germany, however, somewhat lower calls have so far been recorded. Wimmer and Kugelschafter (2017) were able to measure frequencies from 100 to 110 kHz in a winter roost. On average, adult females emit somewhat higher frequencies (mostly> 107 kHz in southern Germany) than adult males (mostly <107 kHz), but there is a certain overlap area in which the calls of sub-adult males can also be assigned (Frühstück 2005). It should be noted, however, that flying juveniles also make calls above 107 kHz in autumn (Wimmer personal communication).

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2.13.3 Social calls Like the greater horseshoe bat, the species can make a variety of social calls. These are almost only to be heard in the roost. As with the greater horseshoe bat, in addition to noisy distress calls, there are especially calls that represent a variation of the location calls and have a long high cf or qcf content. Some of them are probably species-specific (mostly significantly higher than the sounds of the greater horseshoe bat), but are not dealt with here as they are not relevant for identification in the field.

2.13.4 Distinctive call types Due to their characteristic frequency, the cf locating sounds can be distinguished from those of the greater horseshoe bat. However technical devices can sometimes produce similar long and constant- frequency tones (e.g. high squeaking or electromagnetic radiation). However, such signals do not have the typical fm parts at the beginning and end of the signal.

The species cannot be identified in southern Europe, since the calls of the species from those of the Mehely and Mediterranean horseshoe bats cannot normally be separated with certainty.

2.13.5 Criteria for verification of species

• At least one call of the type with Fc between 100 and 116 kHz and with visible fm components at the beginning and end.

78 Bayerisches Landesamt für Umwelt 2020 Final Remarks

3 Final Remarks In order to minimize the risk of incorrect identification, the criteria for the evaluation of acoustic evidence of the individual species in this guide were formulated relatively conservatively. However, it is also intended to help people with little experience in identifying bat calls to familiarize themselves with the topic and achieve reliable analysis results. In general, if there is uncertainty in the call identification, the analysis result should be left at a higher group level. A good knowledge of the biology and distribution of the species helps in call identification. For example, certain species in certain regions of Bavaria can be excluded with a high degree of certainty due to their distribution or an unsuitable habitat. However, the examples of the spreading of the ranges of Kuhl’s and Savi’s pipistrelles show that such exclusion procedures should be used with caution.

4 References Barataud, M. (1996). The inaudible world & The World of Bats: acoustic identification of French Bats. 2 CDs + booklet 47p. Sittelle publisher, Mens (France)

Barataud, M. (2015). Acoustic ecology of European bats. Species Identification and Studies of Their Habitats and Foraging Behaviour. Biotope Editions, Mèze; National Museum of Natural History, Paris. ISBN 978-2-36662-144-0 ecoObs (2020). Batident-Handbuch. http://www.batident.eu/Manual-batIdent.pdf

Frühstück, K. (2005). Quartierökologie und Populationsdynamik der Kleinen Hufeisennase (Rhinolophus hipposideros) im Sommer. Diplomarbeit am Institut für Zoologie, Karl-Franzens-Univ., Graz

Gannon, W. L., O'Farrell M. J., Corben, C. & Bedrick, E. J. (2004). Call character lexicon and analysis f field recorded bat echolocation calls. Pp. 478–484, in Echolocation in bats and dolphins (J. Thomas, C. Moss, and M. Vater, eds.). University of Chicago Press, Chicago, IL. 604 pp.

Hammer, M., Zahn, A. und Marckmann, U. (2009): Kriterien für die Wertung von Artnachweisen basierend auf Lautaufnahmen. Version 1 – Oktober 2009. Koordinationsstellen für Fledermausschutz in Bayern

Jakobsen, L. & Surlykke, A. (2010). Vespertilionid bats control the width of their biosonar sound beam dynamically during prey pursuit. Proc. Natl. Acad. Sci. U.S.A. 107, 13930–13935. DOI: 10.1073/pnas.1006630107

Kopsinis, Y., Aboutanios, E., Waters, D. A. & McLaughlin, S. (2010). Time-frequency and advanced frequency estimation techniques for the investigation of bat echolocation calls. J. Acoust. Soc. Am. 127 (2), 1124–1134. DOI: 10.1121/1.3283017

Middleton, N., Froud, A. & French, K. (2014). Social Calls of Bats of Britain and Ireland. Exeter: Pelagic Publishing

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Nardone, V. A. L. & Russo, D. (2017). A flexible communicator: Social repertoire of Savi’s pipistrelle, Hypsugo savii. Hystrix, the Italian Journal of Mammalogy 28(1), 68–72. DOI:10.4404/hystrix-28.1- 11825

Pfalzer, G. & Kusch, J. (2003). Structure and variability of bat social calls: implications for specificity and individual recognition. J. Zool. Lond. 261, 21–33.

Pfalzer, G. (2002). Inter- und Intraspezifische Variabilität der Soziallaute heimischer Fledermausarten (Chiroptera: Vespertilionidae). Dissertation Universität Kaiserslautern. 251 S.

Runkel, V. & Gerding, G. (2016). Akustische Erfassung, Bestimmung und Bewertung von Fledermausaktivität. Verlagshaus Monsenstein und Vannerdat OHG, Münster

Schnitzler, H.-U. & Kalko E. K. V. (1998). How echolocating bats search and find food. Pages 183– 196 in Kunz TH, Racey PA, eds. Bat Biology and Conservation. Washington (DC): Smithsonian Institution Press.

Seibert, A.-M., Koblitz, J. C., Denzinger, A. & Schnitzler, H.-U. (2015). Bidirectional Echolocation in the Bat Barbastella barbastellus: Different Signals of Low Source Level are emitted upward through the Nose and downward through the Mouth. Plos One 10(9): e0135590.doi:10.1371/journal.pone.0135590

Skiba, R. (2009). Europäische Fledermäuse. Kennzeichen, Echoortung und Detektoranwendung. Wolf, VerlagsKG.

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5 Appendix

Fig. 85: Various short trills of the noctule

Fig. 86: Various long trills of the noctule

Fig. 87: Various long trills of the noctule

Fig. 88: Various short trills of Leisler’s bat

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Fig. 89: Various long trills of Leisler’s bat

Fig. 90: Different "location-call-like" to "arched" social calls of Leisler’s bat

Fig. 91: Social calls of the serotine, similar to the walking stick calls of Daubenton’s bat

Fig. 92: Various trills of the serotine in the habitat and in the roost

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Fig. 93: Different "location call-like" to "arched" social calls of the serotine and one double call in/at the roost

Fig. 94: Various multi-harmonic qcf calls or wavy calls from the serotine in/at the roost

Fig. 95: Different "location-call-like" to "arched" social calls of the northern bat in the hunting habitat

Fig. 96: Various trills of the northern bat (emitted in flight)

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Fig. 97: Multi-part courtship trill of Nathusius’ pipistrelle; sometimes only parts of the call complex are uttered (B and C).

Fig. 98: Various courtship trills of Kuhl’s pipistrelle

Fig. 99: Different bow calls of the Kuhl’s pipistrelle in the hunting habitat

Fig. 100: Various courtship trill of the common pipistrelle bat

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Fig. 101: Different bow calls of the common pipistrelle bat

Fig. 102: Different bow calls of the common pipistrelle bat (the last three are double calls)

Fig. 103: Various courtship trills of the soprano pipistrelle bat

Fig. 104: Different bow calls from the soprano pipistrelle

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Fig. 105: Different bow calls from the soprano pipistrelle (the last three are double calls)

Fig. 106: Selection of different short calls from brown/grey long-eared bat (<4 ms); Overlap of the FFT window 93.75% (see Fig. 73: FFT window 96.875%).

Fig. 107: Different courtship / bow calls of the long-eared bat

Fig. 108: Different social calls of the barbastelle; shorter calls are usually fm calls, while longer calls can be pronounced as arcs or qcf calls.

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Appendix

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