THE EFFECTS OF BUSH CLEARANCE ON AFRICAN UNGULATES IN A SEMIARID NATURE-RESERVE

Bush encroachment has contributed to the diminishing availability of open grassland areas and possibly caused the decline of the local wildebeest and zebra populations in a semi-arid nature reserve in South Africa. Bush was subsequently cleared to convert dense woodland to parkland savanna. Based on an ecological gradient of habitat utilization previously described for African ungulates, it was assumed that wildebeest and zebra would favor cleared areas, whereas impala and kudu would prefer naturally dense woodland vegetation. Measurements of forage production showed that dry matter yield of grasses was greater in cleared areas. Proportion similarity indices and confidence intervals, representing the monthly occurrence of ungulates in different habitats, suggested that wildebeest and zebra were selecting for cleared areas, whereas impala and kudu occurred randomly in cleared and natural habitats. Results suggested that moderate modifications of woodland savanna habitats by means of bush clearance could be advantageous to ungulates that are common in grassland habitats, while not being detrimental to resident dwellers of dense woodland. Managers, however, should consider carefully the application of bush clearance. The response of ungulates was weak, and therefore clearance might not be justified if done for the purpose of propagating grazers.