Grazing by wild red deer: Management options for the conservation of semi-natural open habitats

Maintaining semi-natural open habitats requires biomass removal, which can be achieved by extensive grazing with livestock species. However, implementing this established conservation management strategy in large or access-restricted areas is often not possible. We investigated grazing by wild and free-ranging red deer Cervus elaphus as an alternative conservation management approach on an active military training area in Germany. In grasslands and heathlands protected under the EU Habitats Directive, we quantified above-ground net primary productivity, forage quality and forage removal by red deer over three successive years. To assess synergistic effects between wildlife grazing and additional grassland management measures removing vegetation biomass (i.e. burning, mowing), we conducted our grazing experiment in burnt, mown and untreated grasslands. Annual forage removal by red deer amounted to 35%, 44%, 48% and 59% of the above-ground net primary productivity in burnt, mown and untreated grasslands, and untreated heathlands, respectively. Theoretically, a similar annual biomass removal could be obtained by livestock grazing with 0.54 animal units ha(-1) in grasslands and 0.45 animal units ha(-1) in heathlands. In grasslands, daily rates of forage removal peaked in spring and early summer, whereas in heathlands, forage removal rates were only significant in winter. Forage removal rates in grasslands increased with productivity and forage quality, which were both enhanced in mown grasslands. This suggests mowing can increase grassland attractiveness to red deer. Forage removal rates in heathlands did not relate to productivity or forage quality but to standing biomass. Synthesis and applications. We demonstrate that the quantity of forage removed by wild red deer can be comparable to that of livestock in common conservation grazing systems. The seasonal patterns of forage removal by red deer in grasslands and heathlands coincided with the different grazing requirements of these habitats. Especially in large areas of conservation interest, we therefore encourage attempts to modify current wildlife management strategies to allow red deer to forage in open landscapes, which can contribute to the conservation of semi-natural open habitats and also help to reduce damage in forest stands.