Fallow deer foraging alone does not preserve the vegetation of traditionally sheep-grazed calcareous grasslands.
The goal of this study was to evaluate to what extent wild ungulates (fallow deer) can contribute to the maintenance of semi-natural calcareous grasslands, which are a threatened habitat type (natura 2000 code *6210). In a 10-year exclosure experiment, we tested the effects of ungulate foraging using three treatments: (A) control with combined foraging of herded sheep and wild fallow deer, (B) sheep exclosure with only deer foraging and (C) total exclosure with no foraging. Treatments not grazed by sheep (B, C) were characterized by significantly declining species numbers, litter accumulation and shrub encroachment. Despite high population densities, the effect of fallow deer alone (B) was weak: Succession of woody species was only partly inhibited, while annuals, short-growing and rosette-building plant species were strongly suppressed by litter accumulation. Only the combination of sheep and fallow deer foraging preserved vegetation structure and species richness and led to a promotion of target species. Synthesis and applications. We conclude that we need to continue the traditional land-use forms such as sheep grazing in order to maintain calcareous grasslands. However, we should also raise our awareness for wild animals and analyse more in depth their potential contribution to the conservation management of open habitats.