From Leaves to Roots: Seasonal Dynamics of Wild Boar (Sus scrofa) Use of Understory Plant Resources in a Forest–Agricultural Landscape of Central Poland

Wild boars (Sus scrofa) forage on plant resources located both above and below the soil surface, but it remains unclear whether these resources are exploited simultaneously or used as complementary food pools according to season. This study examined seasonal changes in the use of understory plant resources by analyzing the stomach contents of 470 wild boars collected throughout the year in central Poland. Four dietary fractions were quantified: grass leaves, herb leaves, grass roots, and herb roots. Their frequency and proportional contribution were compared among six phenological seasons using non-parametric statistics and generalized linear models. Significant seasonal differences were found in both occurrence and dietary contribution. Aboveground plant parts, particularly grass leaves, dominated during the Greening and Flowering periods, whereas underground organs became more important in autumn and winter. Herb roots showed the strongest seasonal increase during the Shedding season, while grass roots remained uncommon throughout the year. Our findings indicate that wild boars switch between these complementary food pools according to plant phenology, tracking seasonal changes in the availability and nutritional quality of plant tissues rather than exploiting aboveground and belowground resources indiscriminately. This flexible foraging strategy provides new insight into the ecological mechanisms underlying rooting behavior.