Liczebność i stanowiska bobra europejskiego w Magurskim Parku Narodowym w latach 1996-2021

In recent years, a significant growth in the population of the European beaver Castor fiber L., both in Poland and around the world, has been observed. Beavers significantly transform the natural environment around the sites where they occur. Therefore, it is important to accurately recognize the colonization patterns of new territories by the European beaver and to gain knowledge about the longevity of populations in already occupied areas. This applies especially to areas of natural value, including protected areas. Fieldwork carried out in the spring of 2021, provided information on the distribution of the European beaver and number of individuals in the Magura National Park (MNP) in the Beskid Niski, an arboreous mountain range in southern Poland. The collected data were compared with similar mappings conducted in this Park in 1996 and 2010. This allowed us to characterize the change dynamics of the beaver population in the MNP area and to describe the changes in spatial distribution of sites inhabited by beavers. During the period of 1996-2021, the population of the European beaver increased from 23-26 to 64 individuals in the study area, with a maximum of 68 in 2010. Beaver colonization of ever smaller watercourses draining higher-located catchments and a change in the characteristics of beaver-inhabited sites have been observed. The average number of dam structures within one site as well as site length have increased. Furthermore, the dominant dwelling type has changed from burrows and open-water lodges to bank lodges, which combine characteristics of the two former. We estimate that the period when beavers migrated further up along the watercourses in the studied area was in the years 2010-2021.