Acta Theriologica 41 (2): 113-126,1996. PL ISSN 0001-7051 Otter Lutra lutra distribution in Poland Marcin BRZEZIŃSKI, Jerzy ROMANOWSKI, Jakub P. CYGAN and Bernard PABIN Brzeziński M., Romanowski J., Cygan J. P. and Pabin B. 1996. Otter Lutra lutra distribution in Poland. Acta Theriologica 41: 113-126. In a field survey of Poland in 1991-1994, signs of otters Lutra lutra (Linnaeus, 1758) were found at 1655 (79.5%) of the 2083 investigated sites. Widespread in most of the country, otters were especially common in the lakelands (N Poland), along the western and eastern borders, and in the Karpaty/Carpathian Mts (SE Poland). Two large areas with only few positive sites were identified in Śląsk/Silesia (SW Poland) and central Poland. Otters inhabit the majority of large rivers in Poland, except some sections of Odra/Oder and Wisla/Vistula. The dynamics of the otter population in Poland in recent decades is difficult to investigate, mainly due to the scarce question- naire data from the sixties and seventies, however, present records suggest that the otter has extended its range, and is no longer an endangered species in Poland. Department of Ecology, University of Warsaw, Krakowskie Przedmieście 26/28, 00-927 Warszawa, Poland (MB, BP); Institute of Ecology, Polish Academy of Sciences, 05-092 Łomianki, Poland (JR, JPC) Key words: Lutra lutra, distribution, national survey, Poland Introduction Previous data on otter Lutra lutra (Linnaeus, 1758) occurrence in Poland were scarce since no national field survey had been undertaken. Several authors reported on the results of inquires, indicating that otters occur unevenly in the whole country (Pielowski 1980, Buchalczyk 1983, Romanowski 1984, Sikora 1984). Some areas had been identified as inhabited by relatively large otter populations, eg lakelands (N Poland) and Karpaty/Carpathian Mts (SE Poland). A few regional studies carried out in Pomorze Zachodnie/West Pomerania (Włodek 1980), the Romincka Forest (Brzeziński 1991a) and the Bieszczady Mts (Brzeziński 1991b) revealed many otter localities. Reports on otter distribution, published at the beginning of the 1980s, indicated a decline of otter numbers in Poland (Romanowski 1984, Bieniek 1988). The species was described as rare and endangered in the Polish Red Data Book of Animals (Bieniek 1992) as well as in recent regional reports (Jamrozy 1994). These authors mentioned that only in some areas the otter populations seemed to increase in numbers. Over the last decade an increase in otter numbers has been observed in many regions (Włodek et al. 1989 and pers. inf.). [113]