Impacts of sheep grazing a complex vegetation mosaic: Relating behaviour to vegetation change

The impact of grazing animals on vegetation is usually considered as a single process, despite the knowledge that behaviours such as defoliation and trampling are likely to have different effects. A 3-year study was carried out to assess the different impacts of sheep on a natural dwarf-shrub and grass mosaic, by relating animal behaviour to vegetation change, using a spatially explicit design. Sheep grazed at average stocking rates of 2, 3 or 4 animals ha−1 in six 1 ha plots. Spatial patterns of defoliation were obtained from field measurements of grazing damage, other aspects of behaviour from direct observation and vegetation change from aerial photographs.