Grazing by free-ranging red deer: effective management for semi-natural grassland conservation?

How to maintain open habitats is a critical question for nature conservation, especially if the area of concern is large and difficult to access. Central to preventing natural succession and maintaining protected grasslands is the removal of biomass, which can be successfully achieved by livestock grazing. The effectiveness of grazing by wild-living autochthonous mega-herbivores has not yet been evaluated. On a military training area (Grafenwoehr, Bavaria, Germany) with high density of red deer (Cervus elaphus), we surveyed grassland productivity, forage quality and forage removal by red deer in burnt (B), mown (M) and untreated (U) grasslands (five replicates per treatment) on five dates per year in 2015 and 2016. Forage removal by red deer was 31.5% (B), 42.2% (M) and 44.3% (U) of the average annual net productivity (B: 385 g m-2; M: 486 g m-2; U: 410 g m-2). Forage removal rates peaked at 1.5 to 1.9 g m-2 d-1 between April and June. Forage quality was improved in mown grasslands after mowing. Red deer grazing could reach biomass removal rates comparable to those in extensive livestock grazing systems. Considering red deer as a grazing species could thus expand the established management options for large-scale grassland conservation.