An autecological study of bushbuck and common duiker in relation to forest management.
Allen-Rowlandson, Timothy Simon.
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Frequent reports of damage caused by bushbuck and common duiker browsing on commercially important timber seedlings, and an interest in the potential and feasibility of hunting these two species on State land were the primary factors responsible for the Directorate of Forestry's motivation of this study. The study area at Weza State Forest comprised approximately 21 000 ha of plantations, grasslands and indigenous forests which were considered representative of timbered areas throughout the Natal midlands. Several methods of age determination were investigated and these findings permitted assessments of growth, fecundity and population structure. The physiological condition of both antelope species was examined in relation to age, sex, reproduction and management strategies, and the results discussed in conjunction with mortality patterns. Principal foods of both bushbuck and duiker were determined from rumen analyses while 112 marked animals were regularly monitored to facilitate assessments of habitat selection and levels of spatial and social organisation. of these largely solitary and Estimates of the abundance nocturnal antelope were influenced by local movements in response to the availability of food and cover which varied seasonally and also fluctuated dramatically with forest succession and timber management activities. Although bushbuck and duiker bred throughout the year and had almost identical rates of reproductive performance, different factors were responsible in limiting the sizes of these two populations. All the available evidence gathered in this study indicated that food resources during winter and early spring were inadequate for bushbuck, particularly in 1983 when 33% of the marked population died from starvation and/or exposure. Notable differences in forage utilization and habitat selection inferred little interspecific competition at this time of the year. In contrast, territorial duiker appeared to be susceptible to highly localised habitat modifications (including the availability of food and cover) which occurred throughout the year and resulted from silvicultural and timber harvesting practices. Rumen analyses and quantitative damage assessment surveys revealed that browsing on timber seedlings was usually confined to localised areas during the winter months and was much less severe than had been originally suggested. Conifers were regarded as a starvati~n food and methods of reducing damage to these young trees were recommended for potential problem areas. Both antelope species were considered overabundant at Weza and recommendations for the future management of these populations included the limited utilization of surplus animals, by sport hunting on a sustained yield basis, and methods of manipulating and improving forest habitats.