Seasonal and ecological determinants of wild boar rooting on priority protected grasslands

Abstract

Abstract Wild ungulates can influence various trophic levels, regulating carnivore abundance as well as affecting habitat structure. Conservation problems can arise when high ungulate densities threaten species or habitats with conservation concern. Assessing factors influencing the intensity of their impact is important to identify appropriate measures enhancing the conservation of protected habitats. We assessed seasonal and ecological factors influencing wild boar Sus scrofa pressure on EU priority grasslands in three protected areas of central Italy, by modelling the effects of habitat/topography-related variables, as well as wild boar population density, on indices of rooting activity. We seasonally surveyed 136 sampling plots from spring 2019 to spring 2021 to estimate rooting, and we used faecal counts to estimate wild boar densities in summer. Estimates of density and rooting varied from 3.5 to 22.2 individuals/km2 and from 1.5 to 22.2% of rooted ground, respectively. We detected a clear seasonal trend in rooting activity, that peaked in autumn and winter. We also found a positive correlation between spring-summer rooting and summer density, across sites. Rooting intensity was negatively related to the local extent of rock cover and increased with the size of the grassland patch and with the percentage of forest around each plot. These results emphasise the wild boar tendency to exploit feeding sites in ecotonal areas, i.e., at the interface between forest and meadows, which maximises security and ease of finding food resources. Actions aiming at the protection of focal plants in grassland habitats, as well as reducing wild boar densities, are supported.