Large mammal herbivores can have significant effects on the structure and composition of plant communities. We studied the impacts of an introduced giraffe population on Acacia species at the Ithala Game Reserve in South Africa. Browse intensity and Acacia mortality were assessed in field transects, and in road transects covering the reserve road network. Several Acacia species occurring in high density giraffe areas had high levels or mortality. Populations of Acacia davyi were extinct in areas accessible to giraffe. Most A. caffra trees within giraffe browse height were dead and A. karroo, the most common species, was also heavily affected. Some species including A. torticollis, showed no or very low mortality attributable to giraffe browsing. Healthy populations of sensitive species occurred in areas within, and adjacent to, the reserve in areas with low or no giraffe browsing. Areas too steep for giraffe access formed spatial refuges for these trees. The differential mortality that is occurring as a consequence of giraffe browsing is altering species composition and species distribution in this savanna landscape.
