Ciechanowski / Lutra 2007 50 (2): 107-134 107 Rare or underestimated? – The distribution and abundance of the pond bat (Myotis dasycneme) in Poland Mateusz Ciechanowski 1 , Konrad Sachanowicz 2 & Tomasz Kokurewicz 3 1 Department of Vertebrate Ecology and Zoology, University of Gdask, Legionów 9, 80-441 Gdask, Poland, e-mail: matciech@kki.net.pl 2 Department of Animal Ecology, Nicolaus Copernicus University, Gagarina 9, 87-100 Toru, Poland 3 Department of Zoology and Ecology, Wrocław University of Environmental and Life Sciences, Kouchowska 5b, 51-631 Wrocław, Poland Abstract: The paper summarises the distribution and abundance of the globally vulnerable and nationally endan- gered pond bat (Myotis dasycneme) in Poland and is based on all the available published and unpublished data. The species was recorded in 105 UTM squares, scattered across almost the whole of Poland. In addition fossil remains, mostly from the Holocene age, were found in 13 squares. Evidence of pond bat breeding (nursing) was obtained from 10 UTM squares, restricted to the lakelands of northern Poland and the valleys of the large rivers in the central part of the country. Only two nursery roosts, used respectively by a maximum of 481 and 391 individuals, were found. The remaining summer records (41 UTM squares) were sightings or captures of adult males, non-breeding females or unsexed individuals and were widely dispersed in areas located far from known reproduction sites. The summer roosts (n=21) were located mainly in buildings, bridge crevices and bird and bat boxes. Sixty-seven hiberna- tion sites of pond bat were found, mainly in old fortiications, cellars and caves. 63% (n=42) of them were used by single individuals and only three held 10 or more individuals (maximum n=34). In the two regularly monitored sites the number of pond bats has luctuated in recent years and in one site it even increased. Most of the available bat data (winter censuses, bird and bat boxes, owl pellets, road casualties, fossil remains, mist netting) shows that pond bats account for less than 1% of the Polish bat assemblages. However this igure reached 2.1 - 2.7% (and in one instance 17.5%) of the total number of bats netted in some regions of the northern lakelands. Many areas that are potentially attractive for breeding populations of pond bat have not yet been surveyed, suggesting that the species in Poland may be much more common and numerous than previously thought. Keywords: bats, Chiroptera, Vespertilionidae, endangered species, conservation status, riparian habitats. Introduction In Europe the distribution range of the pond bat (Myotis dasycneme Boie, 1825) extends from southern Sweden, Finland and Russia in the north, to Belgium and France in the west and Croatia, Serbia, Bulgaria and Ukraine in the south (Horáek 1999, Limpens et al. 2000, Benda et al. 2003, Siivonen & Wermundsen 2003). A vagrant individual was recently also found in Great Brit- ain (Hutson 2005). Within this distribution range, reproduction (i.e. nursing) has been observed in the Netherlands, Denmark, northern Germany, Hungary, Latvia, Estonia and Russia (Limpens et al. 2000). The pond bat is a stenotopic species that prefers a lowland landscape with a dense network of patches of still or slow-moving freshwater and uses a specialised hunting tactic (trawling). Its continued survival is a high conservation prior- ity (Horáek & Hanák 1989, Limpens et al. 2000) and it was included in the 1996 IUCN Red List of Threatened Animals and classiied as vulner - able (VU) in the Palearctic Region (Hutson et al. 2001). As a result the pond bat is included in Ap- pendix II of the EC Directive on the Conservation of Natural Habitats and of Wild Fauna and Flora © 2007 Vereniging voor Zoogdierkunde en Zoog- dierbescherming. Lutra articles also on the internet: http://www.vzz.nl