The assessment of a wisent population structure in Bieszczady Mountains

Abstract

Sex and age structure of a wisent population was assessed in Bieszczady Mountains on the basis of routine year-round observations conducted between 2001 – 2012, and compared with a structure estimation based upon analysis of wisent photographs. There were differences found between the western and eastern population of the region as well as among seasons of the year. In western subpopulation there was, according to applied method, a distinct dominance of bulls in both seasons (63.7% in the growing season and 58.5% in winter), while the percentage of calves was at a low level (below 10%), while in the eastern subpopulation, the estimated percentage of cows was generally higher (respectively 38.6 and 48.6%), however its proportion vs. bulls differed between seasons. The percentage of calves was much higher there – at the level exceeding 15% on average. Estimates based on the analysis of photographs gave much lower estimates for bulls: 32.1 and 35.5% respectively in
summer and winter for western subpopulation, and 12.2 and 13.8% for the eastern subpopulation. The percentage of calves however, was assessed at much higher level there: 19.5 and 12.5% respectively. Discussed are reasons for differences in results obtained with both methods.