Ecological separation by browsers on the Lewa Wildlife conservancy, Kenya

Abstract

This study was conducted on the Lewa Wildlife Conservancy in the northern foothills of Mount Kenya. The vegetation of the area forms a transition from a semi-arid highland to an arid lowland and can be physiognomically described as savanna. Plant communities are described in terms of available browse of the woody vegetation. An evaluation of the structure and condition of the woody vegetation indicates heavy utilisation by game. The dynamics of herbivore-habitat relationships were investigated, with the emphasis on ecological separation of the browsers. The target browsers studied were the black rhinoceros Diceros bicomis michaeli, the elephant Loxodonta africana and the reticulated giraffe Giraffa camelopardalis reticulata. Preference for different habitat types, seasonal variations in these preferences, and the selection for specific environmental parameters contribute to the ecological separation of the browsers. A study of the feeding ecology of the browsers revealed that ecological separation is only partly achieved through food plant selection. The large numbers of browsers on Lewa create an excessive demand for browsable food resources, especially during the dry season. The potential for competition between the browsers therefore becomes eminent. A study of the lack of regeneration of Acacia xanthophloea seedlings in the riverine habitats on Lewa revealed that the present stocking rate of browsers is the primary cause for this lack of regeneration.