NATURA SLOVENIAE 21(1): 47-53 Prejeto / Received: 7. 12. 2018 
SHORT COMMUNICATION Sprejeto / Accepted: 25. 4. 2019 
Biotehniška fakulteta Univerze v Ljubljani in Nacionalni inštitut za biologijo, Ljubljana, 2019 
 
 
 
First records of the European free-tailed bat Tadarida 
teniotis (Rafinesque, 1814) in Slovenia 
 
 
 
Primož PRESETNIK, Ali ŠALAMUN 
 
 
Center za kartografijo favne in flore, Antoličičeva 1, SI-2204 Miklavž na Dravskem polju, Slovenija;  
E-mails: primoz.presetnik@ckff.si, ali.salamun@ckff.si 
 
 
 
Abstract. An acoustic survey of bats was conducted throughout 2016 on the slopes of the hill Črna griža near 
Kozina, and from the end of August 2016 to the end of October 2017 on a small Griško polje plateau close to the 
village of Dolenja vas near Senožeče — both sites are located in the south-west of Slovenia. Echolocation calls of 
Tadarida teniotis were recorded at both sites. T. teniotis was recorded near Kozina during 11 nights from April to 
October 2016, but it was rare, with its 38 passes constituting just 0.53% of all bat passes. It was even rarer near 
Dolenja vas where it was recorded twice only on the hill Veliki Ognjivec — in April and October 2017 — where 
constituting only 0.0001% of all bat passes. Both sites are located on the northern border of T. teniotis 
Submediterranean range. T. teniotis is the 31st bat species recorded in Slovenia and the 30th bat species currently 
living in the country. 
 
Key words: Tadarida teniotis, distribution, echolocation, acoustic survey, Slovenia 
 
 
Izvleček. Prve najdbe dolgorepega netopirja Tadarida teniotis (Rafinesque, 1814) v Sloveniji – Leta 
2016 smo napravili celoletni zvočni popis netopirjev na območju hriba Črna griža pri Kozini, podobno študijo pa 
tudi med avgustom 2016 in oktobrom 2017 na Griškem polju pri Dolenji vasi pri Senožečah (oboje v jugozahodni 
Sloveniji). Na obeh mestih smo posneli tudi eholokacijske klice dolgorepega netopirja Tadarida teniotis. Pri Kozini 
smo dolgorepega netopirja zabeležili v 11 nočeh od aprila do oktobra 2016, vendar je bil redek in njegovih 38 
posnetih mimoletov je sestavljalo le 0,53 % vseh mimoletov netopirjev. Pri Dolenji vasi je bil še redkejši, saj smo 
ga na hribu Veliki Ognjivec zaznali le enkrat v aprilu in enkrat v oktobru 2017, kar je bilo le 0,0001 % vseh 
mimoletov netopirjev. Obe mesti najdb ležita na severnem robu submediteranske razširjenosti te vrste. Dolgorepi 
netopir je 31. vrsta netopirjev, najdena v Sloveniji, in 30. vrsta netopirjev, trenutno živeča pri nas. 
  
Ključne besede: Tadarida teniotis, razširjenost, eholokacija, zvočni popis, Slovenija 
 
 
 
Introduction 
 
 
In Europe, the European free-tailed bat Tadarida teniotis (Rafinesque, 1814) has a 
predominantly circum-Mediterranean distributional range, although it reaches as far as 
southern Switzerland, and has even been recorded further north (Dietz & Kiefer 2014). It is 
common along the Adriatic shores in Italy and Croatia (Lanza 2012, Tvrtković 2017) and was 
Primož PRESETNIK & Ali ŠALAMUN: First records of the European free-tailed bat... / SHORT COMMUNICATION 
NATURA SLOVENIAE 21(1): 47-53 
48 
recently found in Italy, very close to the Slovenian border (Lapini et al. 2014, Zagmajster et al. 
2015). Considering its known distribution, the species was long presumed to be present in 
Slovenia as well (Kryštufek 1991, Presetnik at al. 2009). Researchers have tried to confirm the 
presence of T. teniotis in southeast Slovenia (e.g. Kryštufek 1991, Presetnik 2005) a number 
of times by conducting surveys near rocky cliffs with fissures, which are generally its typical 
roosts (Dietz & Kiefer 2014), but all their attempts were unsuccessful. Although Lanza (2012) 
reported the species’ existence near the village of Osp in Slovenia citing Kryštufek (1991), this 
is erroneous, as Kryštufek (1991) merely reported on an unsuccessful survey for T. teniotis. 
However, the results of our present studies finally confirm the presence of T. teniotis in 
Slovenia. 
 
 
 
Materials and methods 
 
 
During 2016, we carried out an acoustic inventory of bats on the hill Črna griža and its 
vicinity (lat. 45.6064°N, long. 13.9238°E, approximately 520 m a.s.l.), close to the town of 
Kozina in the south west of Slovenia. The hill is partly covered by forest stands of Pinus nigra 
of medium age, partly by overgrown meadows and partly by regularly mown meadows 
separated by lines of trees. The valley of the Glinščica River begins on the southwestern side 
of the hill, and approximately 9 km to the west the river flows into the Adriatic Sea, near the 
city of Trieste. On the Črna griža hill we recorded, on 17 evenings from 12 May 2016 to  
13 November 2016, bat calls in 10× time-expansion mode with manually operated ultrasound 
detectors (Pettersson D240x, Pettersson Elektronik, Sweden) and a digital recorder (Marantz 
PMD 670, Marantz Professional, USA). The audio settings were: a) detector: maximum storage 
time – 1.5 s, b) recorder: 16 bit rate, 48 kHz sampling frequency. We also carried out 51 all- 
night surveys (March: 6, April: 6, May: 3, June: 3, July: 6, August: 7, September: 9,  
October: 8, November: 3) with three automatic acoustic recorders, Song Meter SM4BAT FS 
with SMM-U1 ultrasonic microphones protected by windscreens (Wildlife Acoustics Inc., 
Maynard, USA) placed at ground level. The audio settings used were: gain – 12 dB, 16k High 
Filter – off, sample rate – 256 kHz, minimum duration of signal for scrubber – 1.5 ms, 
maximum duration of signal for scrubber – none, min minimum trigger frequency – 11 kHz, 
trigger level – 12 dB, trigger window – 3 s, maximum length of recording – 15 s, compression 
– none. The automatic acoustic recorders also recorded the ambient temperature with a 
precision of 0.25°C for each minute. 
 
A similar study was conducted on a small plateau – commonly known as Griško polje, 
located approximately 2 km west of the village of Dolenja vas near Senožeče. On the plateau, 
there are pastures for cattle, horses, donkeys and sheep, meadows, as well as small forest 
islands. Most of the continuous forest is concentrated on the slopes descending to the west of 
the plateau towards the valley of the small river Raša. The area is situated approximately 
20 km NE of the Adriatic Sea. There we also carried out an inventory using manually operated 
detectors (26 evenings), and 80 all-night surveys with three automatic recorders (2016: 
August: 4, September: 13, October: 8, November: 3; 2017: March: 9, April 4, May: 7, June: 4, 
July: 4, August: 7, September: 7, October: 10). 
 
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In this paper, each separate recording made by automatic recorders is referred to as a 
»bat pass«, and we define a »bat visit« as a group of bat passes made sequentially with 
pauses of less than 3 minutes. We regard such bat visits as an indication of the number of 
separate visits T. teniotis made to the area. All recordings were later analysed with the 
program BatSound 4.0 (Pettersson Elektronik, Sweden). On the spectrogram we manually 
measured the duration of bat calls, the frequency of maximum energy, the start and end 
frequencies, as well as intercall intervals. The program settings for the analysis of T. teniotis 
calls were: FFT size – 1024 samples, threshold – 15, window type – Hanning, segment 
duration – 250-2000 ms per plot. We used echolocation call characteristics described by 
Haquart & Disca (2007) and Barataud (2015) to discriminate T. teniotis calls from the calls of 
other bat species. Specifically, short call duration (e.g. < 20 ms) in combination with low end 
frequency (e.g. < 14 kHz) are, according to the above mentioned authors, characteristic 
enough to separate T. teniotis from observations of Nyctalus lasiopterus which also uses low 
echolocation calls. Characteristically, the echolocation calls of the latter species are usually of 
much longer duration (>20 ms) at the frequencies of maximum energy and end frequencies 
below 14 kHz. 
 
To investigate whether T. teniotis had been more active at certain times of the night, we 
divided each night into ten equal time periods (deciles) and made a visual comparison of the 
number of passes in each particular time period. Our interest was only in the deciles where  
T. teniotis was present, regardless of the fact that the deciles differentiated in absolute time 
length (from 49 minutes to 1 hour and 27 minutes) as the nights differed in length throughout 
the season. 
 
 
 
Results and discussion 
 
  
Surveys with manually operated detectors on the hill, Črna griža, and at the plateau, 
Griško polje, failed to reveal the presence of T. teniotis. Nevertheless, we identified its calls on 
the recordings made with the automatic acoustic recorders. We counted 38 bat passes of the 
species (grouped in 17 bat visits) on 11 nights (Tab. 1) at Črna griža, and 2 bat passes  
(2 visits) on separate nights close to the hill, Veliki Ognjivec, which is above the Raša valley at 
Griško polje. The terminal buzzes of the species were also present on some of the recordings 
at Črna griža. The measured parameters of selected echolocation calls, excluding terminal 
buzzes, were: frequency of maximum energy ranged from 10.6–12.7 kHz, start frequency 
from 11.0–15.0 kHz, end frequency from 10.0–11.6 kHz, call duration from 13–24 ms and the 
intercall interval ranged from 361–1240 ms (N = 14). The combination of the low frequency of 
maximum energy and the low end frequency of the echolocation calls, with the relatively short 
call duration clearly discriminated T. teniotis echolocation calls (Fig. 1) from observations of 
N. lasiopterus, which was also recorded at both areas investigated. We recorded the latter 
species more frequently than T. teniotis, but still very sporadically, on 27 nights (129 passes) 
at Črna griža, and on 32 nights (88 passes) at Griško polje. These sites are the second and 
third locations of recent sighting of N. lasiopterus in Slovenia (Presetnik & Knapič 2015). 
 
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Figure 1. Spectrogram of an exemplary echolocation call sequence and power spectrum of the marked Tadarida teniotis 
call recorded on the hill Črna griža near Kozina in Slovenia. 
Slika 1. Spektrogram primera zaporedja eholokacijskih klicev in jakostni spekter označenega eholokacijskega klica 
dolgorepega netopirja, posnetega na hribu Črna griža pri Kozini v Sloveniji. 
 
Table 1. Dates and number of European free-tailed bat Tadarida teniotis passes on the Črna griža hill in 2016. 
Tabela 1. Datumi in število mimoletov dolgorepega netopirja na hribu Črna griža v letu 2016.  
Night / 
Noč 
Duration of one decile / 
Trajanje ene desetine noči 
[h:min] 
Sum of bat visits 
(no. of bat passes) / 
Število netopirskih 
obiskov (št. mimoletov) 
Decile of the night 
(no. of bat passes) / 
Desetina noči 
(št. mimoletov) 
5.4./6.4.2016 1:05 1 (3) 9 (3) 
15.4./16.4.2016 1:02 1 (1) 6 (1) 
16.4./17.4.2016 1:02 4 (5) 1 (1), 4 (2), 7 (2) 
3.5./4.5.2016 0:57 1 (1) 1 (1) 
13.8./14.8.2016 0:59 1 (1) 5 (1) 
14.8./15.8.2016 0:59 1 (3) 8 (3) 
25.8./26.8.2016 1:02 1 (5) 7 (5) 
10.9./11.9.2016 1:07 3 (13) 3 (6), 4 (2), 5 (5) 
11.9./12.9.2016 1:07 1 (2) 8 (2) 
30.9./1.10.2016 1:13 1 (2) 3 (1), 5 (1) 
1.10./2.10.2016 1:14 1 (2) 2 (2) 
Median / Mediana    - 1 (2) 5 
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The presence of T. teniotis on the hill, Črna griža, was not a surprise as this site (in UTM 
square VL 15) is a mere 9 km ENE from the recent observations recorded by Zagmajster et al. 
(2015) just across the border in Italy (UTM square VL 04). The hill, Veliki Ognjivec at Griško 
Polje (in UTM square VL 26) is approximately 20 km NE from the site in Italy, but still in the 
expected distribution range of the species. 
 
T. teniotis very rarely made an appearance on the hill, Črna griža, because we could 
attribute only 0.53 % of all bat passes (out of 7231) to this species. We recorded 17 separate 
bat visits of the species on 11 nights or 21% out of 51 possible nights. However, it was 
recorded from early April until early October 2016 (Tab. 1) at air temperatures ranging from 
10 to 23 °C. On each recording, the echolocation calls of only one T. teniotis were observed. 
In most cases, T. teniotis visited the area under investigation only once per night, with two 
exceptions. On the nights of 16 April and 10 September 2016, T. teniotis visited the area  
4 and 3 times respectively (Tab. 1). The median number of bat passes per bat visit was  
1 (maximum 6) and the bat visits lasted 4 minutes at most, with the median being 1 minute. 
In general, the median was 2 bat passes by T. teniotis per night, and usually no more than  
5 passes were recorded each night, the exception being the night of 10 September 2016  
(13 passes). At Veliki Ognjivec (Griško polje), one bat pass by T. teniotis was recorded on  
8 April 2017, and one on 7 October 2017, amounting to just 0.0001 % of all the bat passes 
(out of 16759), or on only two nights (i.e. 0.025 %) out of 80 possible nights. 
 
We attribute the lack of T. teniotis records for the months of June and July (Tab. 1) at 
Črna griža, and from May to September at Griško polje, more to its rarity in the areas than to 
less intensive summer samplings. Zagmajster et al. (2015) also reported on the rarity of the 
species in the neighbouring Italian region of Friuli Venezia Giulia (4 out of 820 ultrasound 
detector sites or 0.49%), though they reported the presence of T. teniotis in the vicinity of the 
Slovenian border also from mid-July. Therefore, a possible seasonal variation of the presence 
of T. teniotis in Slovenia and adjacent areas requires further investigation. 
 
Why had this species not been recorded in Slovenia earlier, despite a number of focused 
surveys carried out to ascertain its presence? One explanation may be its rarity, and/or the 
time of night when T. teniotis is active in the area. In the case of Črna griža, most of the 
T. teniotis passes occurred after the first fifth of the night, and over 60% of passes were 
recorded after the second fifth of the night (Fig. 2). Similarly, at Veliki Ognjivec (Griško polje) 
one bat pass was recorded in third and one in forth fifth of the night. Therefore, T. teniotis 
occurred at the times of night when surveys with manually operated detectors had been less 
intensive or not conducted in the past. 
 
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Figure 2. Number of Tadarida teniotis passes in each of the ten time periods (deciles) of the night in the year 2016 on 
the hill Črna griža (for the duration of each decile of the night see Tab. 1). 
Slika 2. Število mimoletov dolgorepega netopirja v desetinah noči v letu 2016 na hribu Črna griža (za dolžino trajanja 
desetine noči glej Tab. 1). 
 
 
 
Conclusions 
 
 
Tadarida teniotis was recorded in areas close to the seashore in the western part of 
Slovenia. The species seems to occur there throughout the year, and therefore should be 
considered a permanent part of Slovenian bat fauna. It is the 31st bat species recorded for our 
country, and is considered the 30th bat species currently living in Slovenia (Presetnik et al. 
2009, Presetnik 2012, Presetnik & Knapič 2015). However, because Slovenia is at the edge of 
its current areal, it is only to be expected that observations of it would be rare, which might 
explain the late confirmation of its presence in the country. We are confident that further 
acoustic surveys, especially using automatic recorders, will shortly reveal more sites containing 
this species in Slovenia. 
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Acknowledgements 
 
 
We are grateful to ENERCOM d.o.o. and AAE Gamit d.o.o. who sponsored our research. We appreciate all the time 
we spent with our colleagues in search of Tadarida teniotis in Slovenia, even when it was in vain, and especially 
acknowledge Klemen Koselj as the spiritus movens for our research, and thank him for keeping his promise to throw a 
big party after the species was finally found in the Slovenian territory. Finally, we would like to express our sincere thanks 
to two anonymous reviewers for their in depth advice on text improvement. 
 
 
 
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