Dry season herbivore utilization of open grasslands in Lower Zambezi National Park, Zambia

Abstract

Utilisation of open grassland plains by large herbivores (≥100 kg) and harvester ants (Messor capensis) in Lower Zambezi National Park, Zambia was assessed every September from 1997 to 2007. A point intercept method was used to estimate percent cover for grass, shrub, bare, litter, herbivore droppings and presence of harvester ants in the Jeki open grassland vegetation community as indicators of range condition. Results showed a reduction in grass cover from 35% in 1997 to 10% in 2007 while litter remained stable. Incidence of herbivore droppings and harvester ants showed a decline while shrub cover and species composition of shrubs increased significantly. As grass cover and grass species composition declined, herbivore droppings and incidence of harvester ants also decreased. Unpalatable species such as Vernonia spp. were assumed to be signs of poor quality range. Increase in bush encroachment indicated heavy utilization by herbivores in the dry season when quality of range deteriorated as a consequence of over utilization of grass species. Further research is required to determine population estimates and grazing capacity of key herbivores such as buffalo (Syncerus caffer). Key words: Range utilization, overgrazing, flood plains, valley floor, shrub encroachment.