Seasonality in Grey Wolf prey selection in the Northern part in the Central Balkan Mountains (Bulgaria)

The main prey of the Grey Wolf ( Canis lupus L.) in the Central Balkan Mountains are wild and domestic ungulates. It was established that the carnivore employed a seasonal selectivity in its prey that was established by analysing Wolf ’s excrements collected in 2018–2020. In winter, the diet included exclusively wild animals, with a differing share of prey species. The biggest share belonged to Red Deer (56.8%). In spring (when the grazing of domestic animals begins), the highest share was to Horses (juveniles) (52.1%), and from the wild animals to Roe Deer (18.8%). During the summer, juvenile Horses again constituted the biggest part of the diet (47.2%), as well as Roe Deer (20.8%). In autumn, juvenile Horses again predominated, with Wild Boar was at second position (15.6%). Ivlev’s selectivity index was used to determine Wolf prey preference ( D ). In respect of Red Deer, Wolves exhibit positive selection of D  = 0.30 for frequency of occurrence in excrements, and of D = 0.21 for biomass. Conversely, Roe Deer are negatively selected during the winter: D  = -0.44 for occurrence, and D = -0.45 for biomass. In the warmer part of the year, the Wolf showed positive selection towards Roe Deer ( D = 0.40), and negative selection for Wild Boar ( D = -0.64 for biomass). From domestic animals, there was strong selection for juvenile Horses in respect of both indexes. Frequency of occurrence is D = 0.98, while use of biomass is D = 0.97. Livestock shows negative selection for both indexes ( D = -0.38) and (-0.31). Sheep occur least of all in the predator’s diet, the coefficient for both indexes strongly showing negative selection ( D = -0.94).