Role Played By Mima Mounds In The Feeding Dynamics Of Herbivorous Mammals In Nairobi National Park

Abstract

Recent studies of Mirna-type earth mounds in Kenya suggest that they differ from adjacent intermound areas in soil texture, plant species composition, primary production and grazing value. This study investigated soil texture, nutrient status and other functional differences between mounds and intermounds within Nairobi National Park during four annual seasons. Soils on the mounds had more clay and silt but less sand and gravel than those of the intermounds. They had higher cation exchange capacity, higher exchangeable calcium and magnesium and higher pH than intermound soils. Mounds provided more favourable conditions for plant growth than the intermounds, Mounds supported a more diverse botanical composition, exhibited a lower coverage of grasses of grazing value and forbs, and a greater coverage of shrubs, than intermounds, a pattern indicative of more intense grazing. Net primary production was higher on the mounds. Death rate of vegetation was higher on the intermounds while decomposition rate of dead vegetation was higher on the mounds during the dry season. The crude protein of the two major grass species and of bulked samples was higher in the mound samples. Weekly animal counts showed preferential utilization of mound vegetation during the dry season and the exclosure method showed higher grazing harvest on mounds.