Vertebrate grazers’ impact on east african savannah vegetation

Abstract

Vertebrate grazers, such as African elephants (Loxodonta africana), plains zebras (Equus quagga), African buffalo (Syncerus caffer), wildebeest (Connochaetes taurinus), and various antelope species, play a crucial role in shaping both spatial and temporal patterns of vegetation in East African savannahs. Through selective foraging, trampling, and nutrient deposition via dung and urine, these herbivores create and maintain distinct vegetation structures, including short-grass “grazing lawns” and taller stands of less palatable grasses. These spatial patterns arise from feedback loops: by repeatedly grazing nutrient-rich patches, herbivores stimulate regrowth of high-quality forage, reinforcing their own feeding preferences. At broader scales, the seasonal migrations of large grazers, such as wildebeest and zebra across the Serengeti–Mara ecosystem, track rainfall and forage availability, producing temporal shifts in vegetation productivity and composition. Grazers also influence fire regimes by reducing fine fuel loads in heavily grazed zones, which limits fire spread and alters the competitive balance between grasses and woody plants, which helps maintain the savannah’s tree–grass coexistence. Additionally, resource partitioning among species of different body sizes and feeding strategies enhances habitat heterogeneity across the landscape. These multiscale processes, combining direct plant–herbivore interactions with indirect effects on disturbance regimes, show the resilience and biodiversity of East African savannah ecosystems, with important implications for conservation management in the face of climate change and megafauna declines.