EVALUATION OF POPULATION STATUS AND FORAGING ECOLOGY OF SABLE ANTELOPE (Hippotragus niger roosevelti – Heller, 1910 ) IN SHIMBA HILLS NATIONAL RESERVE, KENYA

Abstract

The Sable antelope (Hippotragus niger roosevelti- Heller, 1910) is endemic to Shimba Hills National Reserve (SHNR) in Kenya. In the past few decades its population has declined considerably. Despite the alarming decline and resultant localized distribution, little information exists on the species current population status and foraging ecology. The main objectives of this study were two-fold; (1) to determine the current population status, structure and distribution of Sable antelope in the reserve, and (2) to assess aspects of the species foraging ecology in SHNR. Data on the population size, structure and the foraging behaviour of the species was collected in both dry and wet seasons for a period of 24 days each season. Direct total ground count was employed to estimate the population size and structure of the species while systematic quadrats and visual estimation were used to assess the foraging behaviour and food plants of the species. About 93±7 antelopes comprising of six herds and a solitary bull were estimated during the study. Sable population structure showed skewed distribution towards adults (52.7%). There was a significant positive linear relationship between the size of herds and the young individuals in the groups (r = 0.904). However, the observed ratios of age (χ² = 9.071, d.f = 10, p > 0.05) and sex (χ² = 2.174, d.f = 5, p > 0.05) structure of the herds did not vary significantly. Larger herds were observed during dry than wet season (d.f = 6, p < 0.05). Different seasons did not have effect on the diversity of food plants selected by Sable (p > 0.05). However, when choosing foraging habitats, Sable preferred mid slope and gentle flat landscapes between wet and dry seasons respectively (χ² = 23.740, d.f = 3, p < 0.05). Statistical analysis of canopy cover indicated that it did not affect significantly the choice of Sable foraging sites (χ² = 0.843, d.f = 2, p > 0.05). There were strong positive correlations between acceptability and availability of grass species in the Sable feeding sites (r = 0.863) and (r = 0.909) in dry and wet season respectively. The quality of Sable vi forage varied significantly across the seasons with relatively high crude protein (p < 0.05) and phosphorous (p < 0.05) levels reported during wet than dry season. The reported decline in the species numbers and skewed age structure of more adults than young ones in the population indicate lack of stability in the population that needs to be investigated for potential causes. This study recommends establishment of a long-term habitat use monitoring program to precisely determine possible changes in the species foraging habitats. The study also recommends for more local community engagement to raise awareness about the declining Sable numbers and assess their possible roles in conservation of the species.