WILDLIFE MANAGEMENT - BUSHBUCK
Bushbuck biology and management
D T Rowe-Rowe

The bushbuck is one of the most widely distributed antelopes in KwaZulu-Natal, and enjoys popularity with hunters as well as with those who are happy merely to have them on their properties.

Some farmers have recorded the disappearance of bushbuck, some have noted that numbers are decreasing, but on the majority of properties on which they occur, numbers are stable or increasing. 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 of 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.

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.
Commercial forests or timber plantations provide cover in the mature growth stages, but do not provide food. During the early stages of plantation development or after felling and prior to replanting, the forbs and shrubs that grow are eaten by bushbuck.

Damage to pine seedlings in commercial plantations is generally limited to periods when natural food is in short supply.

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 1/20ha (or 5/100 ha). In ideal habitat, where there is plenty of dense cover, and a year-round supply of nutritious food at the correct height for browsing, they occur at 1/8ha (i.e. 12/100ha). Under exceptionally good conditions, the densities may be higher.

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 about 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 63 kg, 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 months. Bushbuck are non-seasonal breeders. A female can conceive about 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.

Threats
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, fruit or vegetables. 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.

Management
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, and an area from which poachers and dogs are excluded. 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 of 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. Furthermore, such fires destroy the forest margin, which is the area in which a variety of plants at the correct browsing height for bushbuck occur. Livestock should be kept out of forests as they too trample and reduce plants in the margin.

Harvesting
Questions, which are asked, are: When is the best time to shoot? How many bushbuck can be hunted? Which animals should be shot?

The first question is easiest to answer: Hold your shoots as early as possible during the hunting season. Bushbuck will be in much better condition at the beginning of June than at the end of July or August. An added advantage of removing animals early in the season, is that the reduction in population density will make more food available to those remaining.

It is difficult to obtain accurate figures on the number of bushbuck in an area. Some farmers, who have been hunting their bushbuck for many years, have a good idea of the population size. Or, if an estimate can be made e.g. from a drive count involving many observers, then this figure can be used - it is likely to be an undercount. A safe figure for annual removal is 10% of the total, but it could be higher, up to 20%.

In KwaZulu-Natal, the tradition is to shoot only male bushbuck and landowners often stipulate "only those with horns longer than their ears". Some of the reasons given for this are that fewer males and more females in the populations will result in more young and a greater population increase; that females are less wary than males and therefore easier to shoot; or that it is unethical to shoot females.

Approximately equal numbers of males and females are born which is why, in populations that are not hunted the sex ratio is 1:1. The continual removal of males only from a population is likely to result in an imbalance. If, for example, ten males are shot, then their ten sisters remain in the population; and if ten young of the year live to replace those shot, then only five will be males - and so on. The eventual high preponderance of females in a bushbuck population does not necessarily mean that the recruitment rate will be higher; it may actually decrease. As bushbuck are solitary, the chances of adult males and females coming into contact with eachother when the female is in oestrus are slim, and if there are too many females and too few males, then the chances of all females conceiving becomes even slimmer.

One should also take account of the fact that not all of the young born in one year will survive to the next. Investigations have shown that shortage of nutritious food during winter is the main factor influencing birth rate and survival of the young. In a population which has reached the maximum for an area, 100 females with insufficient food might produce and rear fewer young than 50 females with sufficient food. Harvesting animals in the same ratio as males may therefore actually increase the size of the calf crop.

Females in many of our bushbuck populations may not be as wary as males and may be easier to shoot, but does this matter if one is removing bushbuck on a sustained yield basis? In some of the large game cropping operations, which have been undertaken, operators have found (as is the case with most other antelope) that the females actually become more wary than males when hunted.

It is unwise to shoot too many of the largest, oldest males. They are key members in a healthy bushbuck population, being most successful at mate acquisition, and will pass their genes for large powerful bodies and long horns on to future generations. Detailed investigations on bushbuck populations have shown that there is no evidence to support the belief that old males become sterile and prevent young males from breeding.

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 a 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.

KEY POINTS
Look after all indigenous bush and forest patches
Forest margins are important in providing food for bushbuck.
Encourage and improve woody vegetation on stream banks.
Check bushbuck habitats regularly for snares, and control dogs strictly.
Shoot bushbuck early in the season.