Habitat suitability for wisents in the Carpathians – a model based on presence only data

Abstract

The study tested an alternative method for the evaluation of habitat preferences of wisents (Bison bonasus) based upon possibly non-biased dataset – presence only data. Data on spatial distribution of free-ranging wisents (3055 individual presence records) were collected over a period of 10 years in the Bieszczady Mountains, south-eastern Poland. Using a nonparametric method of kernel estimators, the density of animal occurrence was calculated. The obtained dot map distribution allowed for spatial analyses of seasonal (winter and vegetative) presence that is related to environmental parameters such as the type of forest stand, dominating tree species, terrain and aspect. According to the final log-linear model, based upon presence-only data, significant differences exist in wisent seasonal preferences for habitat type. Wisents were more commonly found, in both winter and vegetative seasons, on sites with broken canopy closure (85.71% and 86.44%, respectively), as well as on slopes with steepness of 13-17o, with rate of presence of 89.83% and 91.84%, respectively. The most frequented tree association was alnus/pine irrespective of season. During both seasons, the percentage of records of wisent presence was the highest within sites of north aspect (93.22% in winter and 93.88% in vegetative), and on sloping terrain (94.92% and 93.88%, respectively), rather than within valleys or areas of relative flatness. The obtained results allow identification of conditions optimal for those animals unbiased by subjective evaluation of habitat conditions. This approach can be crucial in selecting sites potentially suitable for future reintroductions of wisents in the whole Carpathian range.