The ecology of large herbivores in Hell's Gate National Park, Naivasha, Kenya.
thesisposted on 19.11.2015, 08:49 by John Warui. Kiringe
This study sought to determine the population size, density, distribution, habitat utilization and biomass of large herbivores in Hell's Gate National Park and two neighbouring ranches, Kedong and Kongoni. The study further determined primary production and wildlife grazing in the Park grassland, the effects of wildlife on the vegetation around the Park's artificial water troughs and the effects of Maasai livestock and geothermal prospecting on the Park vegetation. Herbivore counts were carried out in Hell's Gate National Park and the two neighbouring ranches between February 1990 and April 1992. Kongoni, zebra and Thomson's gazelle were found to be the most abundant species. The distribution pattern exhibited by the ungulates in the three areas was neither random or regular, and appeared to be influenced by both topography and vegetation type. Dry and wet season distribution patterns of the wildlife were similar. In the three study areas, most of the herbivores were found to prefer the grassland followed by relatively open shrubland. Areas of dense vegetation and rugged terrain were not preferred. Kongoni, zebra, eland and buffalo contributed the highest proportion of the herbivore biomass. They contributed 82% of the total herbivore biomass in the Park, 85% in Kedong Ranch and 82% in Kongoni Ranch. The herbivore biomass fluctuated monthly depending on population fluctuations, such that when there was a high count of the herbivores in a given month, there was a corresponding high biomass. Above-ground primary production and herbivore grazing were estimated in the Park grassland which was the main grazing area for most of the ungulates. There were two peaks of primary production which coincided with the occurence of the long and short rains, such that there was a significant linear regression between net primary production and rainfall. The monthly amount of dead and live grass biomass fluctuated in response to seasonal rainfall, such that during the dry season the amount of dead biomass increased while that of the live biomass decreased and vice versa during the wet season. There was a significant linear regression of live grass biomass on rainfall, but there was no significant correlation between rainfall and dead grass biomass. The annual productivity of the grassland was 720g/m2/yr, and the total annual offtake of the grass forage by the herbivores was 12.7%. Therefore, most of the grass forage dried up to form dead biomass which was probably of little food value to the wildlife. The effect of both wildlife trampling on the vegetation around three artificial water troughs and illegal livestock grazing on the Park vegetation (in the Narasha area) were studied between April 1990 and April 1992. Overall, vegetation cover between the trampled and untrampled areas of the water troughs did not show any significant difference. Trampling also did not lead to any overall difference in plant species composition, diversity and abundance between the trampled and untrampled areas. Livestock grazing at Narasha did not lead to a significant difference in percentage vegetation cover and mean species diversity between the grazed and ungrazed areas. Although some plant species were only found in either the grazed or ungrazed areas, overall, grazing appeared not to lead to a significant difference in plant species composition and abundance between the two areas. It was therefore concluded that livestock grazing was not altering the Park vegetation in any significant way. The long term future of the Hell's Gate ecosystem (the Park together with the surrounding ranches) as a self sustaining unit requires that its current ecological integrity be maintained. The human activities that are taking place within it, especially expansion of agriculture, will determine its future, and if not controlled will lead to loss of wildlife habitats and a decline in the population size of the various herbivore species found within it.