13 Dec Bushbuck of Zimbali
First impressions count. At Zimbali the overwhelming vista is one of natural beauty, ecological richness and biological diversity. The luxuriance of this reserve is reflected in its eight different vegetation types ranging from pioneer dune vegetation through to towering dune forest. All this provides a secure home to no fewer than 34 mammals and 220 bird species as well as countless butterflies and insects – all of which are vital to the sustainability of these sensitive ecosystems.
Zimbali as a coastal estate prides itself in being home to a healthy bushbuck population. These antelope roam throughout the Estate and provide pleasure to Members and visitors alike. The management programme of these mammals is monitored by the Zimbali Estate Environmental Management Committee and the relocation of existing bushbuck and also the introduction of new blood into the Estate is an ongoing exercise. Due to the absence of predators, the numbers of the bushbuck must be managed to avoid overgrazing and inter breeding. See Page 116 of the Zimbali Fauna Book. The bushbuck is one of the most widely distributed antelopes in KwaZulu-Natal.
In this article, information is presented which may lead to a better understanding of the biology of the bushbuck and perhaps impart some ideas on management.
Diet and Habitat Preferences
Bushbuck eat mainly leaves and soft stems or shoots from trees, shrubs and forbs(small broad leafed plants), while ferns, flowers, fruits, fungi and grass are minor items in the diet. On farms they will also feed on lucerne, oats, or ryegrass, provided that they are fairly near to the bushbuck daytime retreats. See 112 Plants for you and your Bushbuck. A Zimbali publication to help homeowners use plants that are suitable for these animals to browse on.
The most favoured habitats are indigenous forest, thickets or riverine wooded areas, where dense vegetation provides cover. When feeding, bushbuck move to more open localities, such as the forest margins or the edges of clearings, where there is sufficient food plants at the correct height.
Social Organisation and Area Requirements
Solitary animals are most commonly seen. On the few occasions that one sees more than one bushbuck, it is usually a female with her young, which remains in contact with the mother until the age of about eight months. Bushbuck are not territorial, therefore their ranges overlap those of other bushbuck. A dominance hierarchy appears to operate, with the strongest adults breeding and having access to the most suitable areas.
In unhunted populations, the numbers of adult males and females are equal, but where males only have been shot, females predominate.
On average, bushbuck density 1/20 ha (or 5/100ha). In ideal habitat, where there is plenty of dense cover, and year-round supply of nutritious food at the correct height from browsing, they occur at 1/8ha (i.e. 12/100ha). Under exceptionally good conditions, the densities may be higher. At Zimbali the density is at about 1Bushbuck to 1 hectare of suitable habitat. Zimbali Estate Management Association (ZEMA) is removing Bushbuck from the Estate to reach the density of 1 Bushbuck/ 3 hectares of suitable habitat.
Reproduction and Development
Males are sexually mature at 11 months, but are prevented from mating by the older, larger, more dominant males. Horns first appear at 14 months, they equal ear length at 21 months, and are 1,5 x ear length at 30 months when the colour change is usually complete. Bushbuck males, which have a mean mass of 63kg, grow throughout their expected lifespan of 13 years. Generally, the older the animal, the longer its’ horns, but trophy horns (longer than 380mm) have been recorded in 7 to 10 year olds.
Females, which reach their mean maximum weight of 36kg at 3 years, usually have their first young at two years, after a gestation of 6 weeks after giving birth; therefore it is possible to have an infant every 8 months. The reproduction rate will, however, depend on bushbuck populations’ density and the year round food supply.
In most parts of KwaZulu-Natal stored fat reserves are highest at the end of Summer when the bushbuck reach a peak condition and are lowest at the end of Winter or early Spring.
Although widespread in KwaZulu-Natal, there are some threats to bushbuck; the most important of which are loss of habitat and habitat changes.
Much indigenous bush has been cleared for the planting of crops and housing developments. Numerous forest patches all over KwaZulu-Natal are shrinking, owing to the practice of burning grassveld right up to the forest. Indigenous forest patches have also suffered from the planting of commercial timber right up to them, therefore reducing or removing the forest margin, and from felled commercial timber falling into the forest.
Poachers that actively hunt or set snares for bushbuck, and uncontrolled dogs have serious effects on numbers. A biological problem that has manifested itself is the introduction of Nyala to farms on which bushbuck occur and where Nyala did not formerly occur. The Nyala, which belongs to the same family as the bushbuck, is a larger animal. It too lives by browsing, but being larger than the bushbuck requires more food and can reach browse, which the bushbuck cannot. If the introduced Nyala do well in an area, their numbers increase rapidly and the bushbuck numbers decline, sometimes to levels of local extinction. The Nyala threat is not applicable at Zimbali.
Management may be aimed at building up a bushbuck population, which can generally be achieved by habitat improvement and protection. The important requirements for bushbuck are suitable cover, the right type of food. Once the population has reached the maximum for the area one can consider another aspect of management, namely that of using the surplus.
Special care should be taken of all patches or indigenous bush and forest – no matter how small the patch. To prevent these patches from shrinking, ensure that veld fires do not burn right up to them, as each time this happens, the forest recedes a little. Not really applicable to Zimbali where the Bushbuck are not hunted and the habitat is managed by ZEMA.
Current Legal Status
(regulations for the new conservation act still have to be promulgated)
In KwaZulu-Natal, by request of our hunters and landowners, the female bushbuck is classified as “protected game” and may only be shot on a permit issued to the landowner. The male is “ordinary game” and may be shot by anybody in possession of a hunting license, who has the landowner’s permission, during the hunting season. Landowners who wish to remove females for management purposes should contact the KwaZulu-Natal Nature Conservation Service. A permit is issued free of charge after consultation with the District Conservation Officer in the area.