Population ecology of oribi, grey rhebuck and mountain reedbuck in Highmoor State Forest Land

Abstract

Populations of oribi, grey rhebuck and mountain reedbuck in Highmoor State Forest Land experienced seasonal population fluctuations that were unrelated to jackal predation. All three antelope species had a peak in deaths during the winter months, and it is possible that winter malnutrition is a major population-limiting factor. In oribi, the sex ratio did not depart significantly from unity, but in both grey rhebuck and mountain reedbuck the ratio was very significantly biased in favour of females. Both grey rhebuck and oribi had a significant peak of births in the summer months, whereas mountain reedbuck bred throughout the year. Mountain reedbuck favoured the steeper valley sides with their scattered Pro tea tree-veld and avoided the plateau area occupied by oribi and grey rhebuck. The overall standing crop of all three species was very low when compared with the estimated potential carrying capacity for wild ungulates in highland sourveld. Home range estimates were made for oribi and grey rhebuck, and all three species were compared on both crude and ecological density basis. Provisional observations on social organization suggest that all three species may be territorial.