An integrated approach to the management of common reedbuck on farmland in Natal.

Abstract

This study was motivated by the Natal Parks Board which has been receiving a growing number of complaints from farmers concerning reedbuck grazing of commercial crops. The reedbuck is an important conservation species, which has recently disappeared from 80 % of its previous range in South Africa, and has become extinct in the Cape Province and the Orange Free State. The study was intended to look objectively at the crop damage problem and conservation status of reedbuck on private land in Natal, and make recommendations for management. A postal questionnaire was used in assessing the species' present distribution in Natal, and an intensive study was undertaken in the Underberg district of the Natal highlands. The study area comprised approximately 10 500 ha of semi-intensive agricultural land, divided into 23 farm properties, and was considered representative of farmland throughout the highland and midland regions of the province, where nutritious food in the form of irrigated pasture grasses is available throughout the year. Four animal census techniques were critically evaluated, and reedbuck numbers assessed throughout the study area. The study area was divided into no-cull, low-cull and high-cull blocks, and population trend examined over two years in each. Population stability was demonstrated in all blocks. Post mortem examination of nearly 200 reedbuck showed that the animals were in excellent physiological condition throughout the year, and the population appeared to be at, or close to its genetic potential as regards productivity. A 20 % annual 'surplus' of animals appeared to be produced. Eighty four reedbock were marked, and resightings of some of these far from their place of capture confirmed that emigration of young animals is an important population regulatory process. A multiple regression analysis of reedbuck-habitat relations, based on observed reedbuck numbers on the 23 farm properties, demonstrated that population size appeared to be llinited by the availability of cover. An examination of social organisation and behaviour led to the belief that cover is limiting because it is a resource that is monopolised by dominant territorial males at the time when females are attracted to it to give birth. Within two months these females, nursing their newborn lambs, become oestrous again, and are mated by the territorial males. Because of the relatively low densities at which stability is achieved, crop damage only becomes a problem in exceptional circumstances. A best estimate of 0,2 t of pasture grass lost per reedbuck per winter was made.