Session

Large herbivores (≥45 kg) play a crucial role in sustaining biodiverse and heterogeneous grasslands. They shape plant diversity and vegetation structure through consumption of plant biomass. Thus, differences in diet between large-herbivore species are crucial to understand their impact on vegetation and plant species richness. We investigated proportions of plant growth forms and richness of plant genera in the diet of semi-wild populations of horse (Equus ferus caballus), cattle (Bos taurus taurus), and bison (Bison bonasus). First, eDNA was extracted from 350 dung samples collected in 11 rewilding sites located in Central Europe. Next, a list of plant genera present in each sample was obtained by sequencing the ITS marker and matching the sequences to corresponding taxa. To evaluate differences in the relative proportions of plant growth forms and the number of plant genera in the diet of large-herbivore species (cattle/bison/horse) linear mixed effect models including site as random intercept were fitted. Cattle, horse, and bison differed in their diet. Horses were consuming more grasses (p < 0.001) compared to cattle and bison. Horses also had the highest proportion of forbs in their diet (p < 0.001), followed by cattle, and bison (p < 0.001). Bison had the highest proportion of shrubs in their diet (p < 0.001), followed by cattle, and horse (p < 0.001). Horse diet was marginally poorer in genera (p = 0.091; avg. = 24) than that of cattle (avg. = 26), and bison (avg. = 31). These results indicate that all three studied large-herbivore species play an important role in sustaining species-rich and heterogenous grasslands, complementing and potentially facilitating each other in their impact on vegetation. In line with previous studies horses appear crucial for suppression of expansive grass species, while bison should counter shrub dominance the most.