Habitat correlates of wild boar density and rooting along an environmental gradient

In wild ungulates, habitat choice usually is influenced by foraging constraints and predator avoidance, potentiallyleading to spatial variation of population density (e.g., greater densities in food rich or safer habitats). Assessing habitatcorrelatesof abundance and foraging activity in turn is important in understanding determinants of distribution. Weassessed habitat correlates of presence, density, and rooting, for wild boar Sus scrofa, the most widespread ungulatein the world, in six protected areas of central Italy. We worked along an altitudinal gradient ranging from the coastto mountains, in late spring-summer 2019. We surveyed 617 sampling plots randomly placed onto study areas withtessellation stratified sampling, where we used fecal counts to estimate wild boar density and visually estimated theproportion of rooted area. Overall estimates of density and rooting (± standard error) varied from 3.5 ± 2.0 to 17.9 ±5.4 individuals/km2 and from 1.4 ± 0.8% to 10.9 ± 1.1% of rooted ground. Density and rooting showed a moderateyet nonsignificant correlation across sites. Probability of presence, abundance, and rooting in sampling plots werehigher in ecotone habitats (transition habitats between wooded and open areas). Topography did not influence boarpresence or local abundance. Rooting increased with decreasing slope and rock cover, as well as increasing elevation,possibly due to soil supporting forage of higher nutritional quality. Our results support the importance of ecotonehabitats for wild boar, emphasizing the role of these transitional areas in the period of nursing/weaning of offspring,as well as when crops are actively growing. Differences in overall estimates of rooting across study sites may dependon site-specific features (soil moisture and availability of alternative food resources). Future studies should test thecorrelation between inter-annual differences of rooting and changes in population density. Notwithstanding the latter,we identified significant ecological drivers of wild boar density and rooting activity.