European Beech Masting Cycles and the Spatial Distribution of Wisents in the Bieszczady Mountains, Poland

The variability of food resources considerably affects the habitat preferences of animals. In mast years, the availability of highly nutritive food increases significantly. We tested whether changes in the distribution of the areas of wisents, Bison bonasus L. concentration, in the Bieszczady Mountains, Poland, were connected with the availability of beechnuts. In the two beech masting years of 2013 and 2022, we considered the months with the highest availability of beechnuts, namely September and October. The beechnut crop varied significantly between as little as 2.4 g dry matter/m², recorded within the Baligród herd’s home range in 2013, and up to 238.8 g dry matter/m² within the Tworylne herd’s range, also in 2013. The analysis of the spatial distribution of beech stands within various parts of the wisents’ home range showed that within the 95% kernel area, their share was mostly high, varying between 25.7% and 42.8%. Meanwhile, within the 50% kernel area, it was generally much lower, except for the year 2022 in the case of the Baligród herd. The densities of wisents varied significantly between the kernel areas of 95% and 50%, ranging between 0.04 and 0.08 animals/ha and 0.17 and 0.48 animals/ha, respectively. However, there was no statistical difference between the figures for all plots tested within the home range of the wisent population and plots dominated by beech. Based on the data obtained in this study, habitat selection patterns of wisents in the Bieszczady Mountains cannot be explained by the availability of beech stands and the phenomenon of mast years.