Diet of wolves and selection of wild ungulates in an area of Northern Italy

The trophic ecology of wolves was studied in a mountainous area of the Italian Northern Apennines from 2007 to 2012. We defined the selection process of wild ungulates to highlight seasonal variations in dietary habits of the wolf in relation to prey abundance. During the study period we collected wolf scats and recorded signs of prey and competitor presence along a network of transects randomly chosen and representative of the different habitats in the area. The results of this study were expressed as frequencies of occurrence and mean percent volumes of prey species. We analysed wolf scats to identify the main food groups consumed by the predator in every season and we compared the proportions of biomass of wild ungulate species in the diet with those calculated with the signs of presence. Annual and seasonal variations in mean percent volumes of food categories and wild and domestic ungulate species were analyzed using nonparametric multivariate analysis of variance. We calculated Levins’ B index to assess wolf diet breadth; in particular, the index was calculated for every season summing up years and for every year summing up seasons. In order to assess the pattern of selection of wild ungulates we calculated the Manly a index. We observed a decrease of diet breadth in the study period, with an increasing use of wild ungulates and a decreasing consumption of livestock, depending on the increase in the availability of wild prey species. Significant seasonal variations were observed in trophic habits of the wolf, but generally there was a wide use of wild ungulates (63.6% in volume summing up years and seasons), especially >1-year-old wild boars. Livestock (20.6% in volume summing up years and seasons) was mainly taken in summer, which corresponds to the period of greater presence of domestic ungulates on pastures. The analyses of selection patterns showed that wolves use either the available prey species, exploiting each species in relation to its abundance and accessibility. Considering the four years of study, it is possible to hypothesize the existence of functional responses of wolves to changes in abundance of the main prey species. The highlighted change in wolf diet, towards a greater use of wild ungulates and a strong decrease of the impact on animal husbandry, is an important step in the process of recovery and conservation of the wolf.