Results of the pioneer survey of potential bat hibernacula in Albania (2012–2015)

. For the first time at a national scale in Albania, a winter bat population census in potential hibernacula has been implemented during the four winters (early 2012, 2012/2013, 2013/2014 and 2014/15). 178 potential hibernation sites have been visited. During the visits of natural caves, bunkers, tunnels, buildings and mines we recorded at least 9 bat species: Rhinolophus ferrumequinum (28 sites), R. hipposideros (36 sites), R. blasii (1 site), R. euryale (3 sites), Myotis myotis/oxygnatus (blythii) (4 sites), M. capaccinii (6 sites), Pipistrellus sp. (2 sites), Hypsugo savii (1 site) and Miniopterus schreibersii (9 sites). The data presented are substantial additions to knowledge on the distribution of these species and their roosts in Albania, and will form a basis for bat population monitoring and, at the same time, for improving conservation measures in Albania and the wider region.


Introduction
Since the first data on bats collected in Albania a century ago, with a female P. auritus caught in 1914 (Spitzenberger et al. 2001), surveys on bats in Albania have been organised during spring, summer or autumn (Hanak et al. 1961, Hurka 1962, Hanak 1964, Lamani 1970, Bego & Griffiths 1994, Chytil & Vlašin 1994, Uhrin et al. 1996, Sachanowicz & Ciechanowski 2006, Sachanowicz et al. 2006, Schieffler et al. 2013, Théou & Bego 2013).Thanks to all these surveys carried out mostly by foreign researchers, 32 bat species were confirmed to occur in Albania (Bego & Théou 2014).With the exception of three records concerning R. hipposideros, M. capaccinii and Plecotus sp., coming from bat surveys of a few caves around Lake Prespa in February 2011 (Papadatou et al. 2011), no other winter data on bats had been collected in this country, even though there are numerous potential bat hibernacula, e.g.thousands of caves and hundreds of former military buildings (Théou 2014).In 2012, a pilot bat monitoring programme focusing on bunkers around Tirana was started by Théou & Bego (2014), and since then at least a few hibernacula have regularly been monitored for the first time in Albania.Even at the scale of wider region, the lack of knowledge about bat hibernacula is apparent, with rare winter observations available for Bosnia and Herzegovina (Pašić et al. 2013), Montenegro (Presetnik et al. 2014), Macedonia (Kryštufek et al. 1992) and Greece (Papadatou et al. 2011).Nevertheless, winter data on bats and their roosts are key elements to understand the bat species conservation status and for implementing a successful management at local and regional level (Dietz et al. 2009).Therefore we hope that the reported results of bat winter surveys in Albania have improved the knowledge on bats not only for Albania, but for the neighbouring countries as well, contributing to the clearer status overview for the south-west Balkan area.

Material and methods
Surveys were organized between mid-November and end of February, spanning four winters (early 2012, 2012/2013, 2013/14 and 2014/15) in several parts of Albania (Fig. 1).In these areas, as in most of Albania, winters are known to be severe, with possible important snow covering, and long period of low temperatures.For some of these areas, annual monitoring programs have been on-going.In general, one visit per winter has been implemented for most of the sites.Natural caves (horizontals and pits) but also bunkers, tunnels, buildings (church, castle, private house, school) and mines were visited in order to identify possible bat hibernacula.These sites have been selected following previous surveys during spring or summer, but several sites have been randomly visited following indications on presence of bats by local inhabitants.For each site visited, the geographic latitude and longitude coordinates were recorded.Bats were counted visually thanks to head lamps and determined down to the species level when possible or attributed to higher taxon following Dietz et al. (2009).In some cases bat detectors (D1000X Petterson Elektronik AB, Sweden) were used at the site to record any bat ultrasound calls, which were eventually analysed with Bat Sound, v4.1 programme (Pettersson Elektronik AB, Sweden) and calls identified according to Barataud (2014).When larger bat groups were encountered, pictures were taken and the number of individuals of each species determined later on the computer.During all surveys, a strict protocol was implemented in order to limit the disturbance of bats with, for example, a limited number of persons checking the roosts to avoid making any noise.No bats were manipulated by hand for direct measurements.

General results
In total, 178 potential bat hibernacula have been visited in Albania (Fig. 1), and 245 visits made thanks to the implementation of monitoring protocols (Tab.1).Of the 178 sites, 114 were caves, 28 bunkers, 22 tunnels, 9 buildings and 5 mines.In 51 (28%) of these sites (27 caves, 8 bunkers, 14 tunnels, 1 building and 1 mine, Tab. 2) at least 9 bat species have been observed (Tab.3).A maximum of five species were recorded in the same hibernacula, whereas a maximum number of 2,431 individuals from three species were recorded in one site (Tab.2).72% of the hibernacula hosted less than 10 individuals, whereas at 15% of the sites more than 100 individuals were found.Most important bat groups composed of more than 500 individuals have been observed in 5% of the hibernacula.
Although hibernating bats were recorded in all types of sites, caves hosted the most important diversity (a maximum of 5 species) and the most numerous groups of bats (maximum of 2,431 individuals) (Tab.2).In comparison, bunkers hosted a maximum of 4 species and 71 individuals, tunnels 4 species and 23 individuals, mines 1 species and 1 individual, buildings 1 species and 1 individual.However, despite this general observation, former military buildings and mines are interesting roosts for some bat species on a local scale, especially for hibernacula, when natural caves are missing in the area (Théou & Bego 2014), which is the case in most of the western part of Albania.
Bat species are distributed differently in Albanian hibernacula.Whereas Rhinolophus ferrumequinum or R. hipposideros have been commonly recorded in hibernacula throughout the country, not only in caves but also bunkers, buildings and mines, other species as Miniopterus schreibersii have been encountered only in a few caves (Tab.2, Figs. 2, 5).This observation seems to be similar to other data collected in other countries of the region (Kryštufek et al. 1992, Papadatou et al. 2011, Pašić et al. 2013, Presetnik et al. 2014).Also, the repeated visits made within the framework of this study showed that identified roosts had been used for several years in a row, especially the roosts hosting more than 50 individuals.Small fluctuation in the number of bats using these sites have been observed, but with data collected during three winters at maximum we cannot give any reliable interpretation of potential trends.However, these results confirm the importance to establish the monitoring protocols for all hibernacula, in order to be able to observe possible changes at the local but also national scale in the future.
It is also important to underline that, contrary to other types of surveyed sites, most of the caves used during the winter were unused by bats during the spring and summer (Théou, unpublished).This aspect has to be taken in account by managers and for the redaction of future management plans, in order not to base management measures only on data collected during spring and summer.The use of several roosts during the year underlines also the importance of creating protected cave networks at a local, national and regional scale.Four years of winter surveys and monitoring of selected sites have substantially increased the knowledge on several bat species in Albania, and in the south-west Balkan region in general.This is the case for the usual cave-dwelling species and also for bat species that are not often found in Albania during spring or summer, as they are using, during these particular periods, human-made habitats that have till recently been surveyed to a lesser extent in the country (as R. ferrumequinum and R. hipposideros).Winter represents an interesting period for the survey of such species, as they can be observed often in caves, bunkers and tunnels.This study, however, represents only a start and the results provided herewith should be used as a base for planning research in the next years in the country.The search for new hibernacula should be intensified and monitoring network expanded according to new knowledge.Regular monitoring of a large number of sites will enable us to follow the trends in bats population size and status of habitats in Albania.Such data can easily be incorporated into regional and European bat population monitoring protocols (Van der Meij et al. 2015).

Rhinolophus hipposideros (Bechstein, 1800)
Most of the 51 observations in the 36 hibernacula identified for this species concern only few individuals (Fig. 2b).37% of the records are solitary individuals, whereas 86% of the records are from sites hosting less than 5 individuals.Only one cave site (AL0437) hosted more than 10 individuals (2%).

Rhinolophus spp. (middle sized)
During the surveys, it was sometimes possible to identify bats as Rhinolophus euryale (Blasius, 1853) or Rhinolophus blasii (Peters, 1866), using bat-detectors and/or pictures.At most of the sites, however, the identification was possible just down to the taxon Rhinolophus of middle size.In Albania, most of the data concerning these species come from the winter census, whereas the number of known maternity colonies is still low (Théou, unpublished).During our study, important winter groups have been recorded, sometimes with less than 200 metres between two caves hosting more than 500 individuals each (sites AL0347 and AL0348).This situation may underline the possible importance of a network of roosts used by bats, with exchanges between the two groups (Bagrowska-Urbańczyk & Urbańczyk 1983).
Additionally to the above mentioned species, Rhinolophus mehelyi (Matschie, 1901) could also have been using the hibernacula, as this species was recently identified in the country (Bego & Théou 2014).42% of the 19 observations concern sites with less than 10 individuals, whereas 26% of the data concern sites hosting more than 200 individuals (Fig. 3).

Myotis myotis (Borkhausen, 1797) / Myotis oxygnatus (Monticelli, 1885)
The two species cannot be clearly identified without taking detailed morphological measurements.In accordance with our strict protocol and in order not to disturb animals, we have referred to those few sightings of all large Myotis sp. as taxon Myotis myotis/oxygnatus.In official documents concerning bats protection in Albania, M. oxygnatus is descripted also as M. blythii (Bego & Théou 2014).During spring 2014, close to 9,000 M. myotis/oxygnathus were recorded during surveys (direct visits of roosts) organised in the entire country and concerning all types of roosts (buildings, caves, tunnels and bunkers).During the winter surveys, however, we observed only four animals at four sites scattered across the country.The difficulty of recording these species during winter seems to be similar in the entire region (Pavlinić et al. 2010), certainly due to the possible use of crevices by individuals (Dietz et al. 2009).However, these rare observations show, at least, that these species seems to hibernate all over Albania (Fig. 4).Observations (ex. is used as abbreviation for individual(s)): -AL0063: 13.11.2014, 1 ex.-AL0293: 6.12.2014, 1 ex.-AL0397: 13.12.2014, 1 ex.-AL0270: 29.1.2015, 1 ex.

Myotis capaccinii (Bonaparte, 1837)
For Myotis capaccinii, most of the maternity colonies are known from the area of Lake Prespa, where we have found the biggest winter congregation of the species (Fig. 4).This is concordant with Papadatou et al. (2011)

Pipistrellus sp.
Considering the high possibility of wrong identification of Pipistrellus bats based on observations only, we considered all the individuals of this genus as Pipistrellus sp.It is highly likely that more than one species of this genus is hibernating in Albania, as all four species have been recorded during spring and summer (Bego & Théou 2014).The hibernating groups were recorded in the vicinity of Lake Shkodra, and underline the importance of bunkers as roosts for bats.The number of these roosts is now strongly decreasing due to illegal destructions, which represent a significant threat for several bat species in Albania (Théou & Bego 2014) (Fig. 4).

Hypsugo savii (Bonaparte, 1837)
The first record of this species during the winter period in Albania was made in the crevice of a bunker, where one animal was hiding among dozens of Pipistrellus sp. (Fig. 4).The individual was well visible, which allowed us to clearly identify it following Dietz et al. (2009).This is the first hibernaculum known for the species in the country, and the species is very likely common in the entire country (Uhrin et al. 1996).It also underlines yet again the importance of bunkers in bat conservation in Albania (Théou 2014).

Miniopterus schreibersii (Kuhl, 1817)
The data collected in Albania must be interpreted on a scale of the south-west Balkans.A colony in the cave (site AL0392) in the north-eastern part of the country represents the third biggest known winter group for this species in the south-west Balkans (Papadatou et al. 2011, Presetnik et al. 2014, Théou & Đurović, unpublished) (Fig. 4).However, the actual knowledge of winter roosts of this species is still unsatisfactory, especially when compared to the summer population in Albania (approximately 6,000 individuals in 2014 (Théou, unpublished data)).The main maternity colonies are located in the area of Lake Prespa.Considering the annual migratory behaviour of M. schreibersii, it is possible that many animals from these roosts migrate to Greek or Macedonian hibernacula.At the same time, some important hibernacula identified in north-east Albania may harbour a part of summer populations from Kosovo.The site AL0392 represents 91% of all the individuals recorded during the winter 2014/15 and

Table 1 .
Number of potential bat hibernacula in Albania visited each winter, from early 2012 to 2014/2015.Numbers in brackets refer to sites visited for the first time in that winter.
data.Only mono-specific groups have been found at all these sites.