Bushbuck ecology and management at Shongweni Dam and Game Reserve.

Abstract

Msinsi Holdings (Pty) Ltd are considering the introduction of nyala to Shongweni Dam and Game Reserve in KZN. This reserve has a naturally resident population of bushbuck and is located beyond the natural distribution of nyala. Concerns for competition between these two species causing declines in bushbuck numbers elsewhere prompted the present study. The main aim of the present study was to determine some aspects of the ecology of bushbuck within the reserve to assist with decision-making regarding the introduction of nyala and species specific-management of bushbuck at the study site. Bushbuck home range and habitat utilisation was investigated with the aid of radio telemetry and Geographical Information Systems. Estimates of total home range size for males using minimum convex polygons (MCPs) and fixed kernels (FKs) were 33.9 ha and 32.1 ha respectively. Estimates of total home range size for females using MCPs and FKs were 12.0 ha and 13.5 ha respectively. A significant difference between total home range size for gender (male and female) was found but there was no significant difference for age (adult and subadult). Bushbuck typically utilised one core area within their home ranges in which 50 % of their time was spent in approximately 17 % and 11.7 % of their total home range for males and females respectively. A substantial overlap in total home range and core areas between animals was found. Bushbuck showed preference for short thickets and avoidance of low closed grasslands. High reedbeds were utilised in proportion to their availability and tallwoodlands were not utilised by the study animals, but were observed to be utilised by other non radio-collared bushbuck. Habitat preference was a consequence of favourable cover being provided by the structure of the vegetation and the occurrence of favourable foraging species. Bushbuck utilisation of topographical aspect was largely determined by the vegetation type that occurred on the respective slopes. Estimations of bushbuck density and abundance were made using sighting efforts, drive counts, and mark-resightings. Sighting efforts using distance sampling during spring were found to be the most effective in terms of accuracy and man-hour costs, however, these were still not considered to be precise estimations of the total bushbuck population at SDGR, but would be useful for monitoring population trends as a result of the high repeatability and simplicity of the method. Sex, age ratios and nocturnal activity were determined using field classification. The field classification method of age and sex ratio determination used during the present study was found to be very subjective and was therefore suggested to have produced ratios which may be largely biased towards the female component of the population. This in turn also effected the determination of social organization and was evident when compared to previous studies. Bushbuck activity determined from radio telemetry and sighting efforts produced results that corresponded with all previous studies, showing bushbuck to be largely nocturnal, moving much larger distances at night than during the day, and spending most of their time walking and feeding at night. The status and management of synoptic bushbuck and nyala in KwaZulu-Natal was also investigated by means of a questionnaire survey. From the opinions of landowners and reserve managers, the status of bushbuck sharing a sympatric relationship with nyala in KwaZulu-Natal (KZN) appeared to be stable to declining, whereas nyala status was increasing. This trend was suggested to be a result of competition for resources between the two species. Northern KZN recorded a higher frequency of this trend (57.7%, n = 26) compared to the Midlands (35.7%, n = 14), as did Ezemvelo KZN Wildlife Reserves (85.7%, n = 7) compared to privately owned properties (42.4%, n = 33). Very little species-specific management for nyala and bushbuck occurred in reserves that participated in the present survey.