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THE GREY DUIKER

14 April 2014

www.leopard.tv

The grey duiker Sylvicapra grimmia is sometimes called the common duiker because it occurs so commonly in Africa south of the Sahara. It is often also called a bush duiker or Grimm’s duiker. The latter name, as its scientific name indicates, is in honour of the explorer R Grimm who first read a description of a grey duiker that was seen at the Fort in Cape Town. Grey duikers are a valuable asset on a wildlife ranch but are often overlooked. They are also commonly being used as bushmeat by the rural people in Africa.

There are many types of duiker in Africa where their subfamily, the Cephalophinae, first developed some 6 million years ago in the deep forests which covered most of Africa then. Nevertheless, duiker-like fossils are known that are some 12 million years old. This makes the duikers one of, if not the oldest, types of antelope in Africa. They occupy a diversity of habitats and are known as three genera with Cephalophus, to which the red duiker Cephalophus natalensis belongs, being the most diverse. The blue duiker Philantomba monticola is relatively rare. Sylvicapra is a monotypic genus because it only contains one species, although its wide geographical range has lead to the development of at least 11 subspecies. Abbott’s duiker Cephalophus spadix is unusual because it occurs on the highest peaks of Mount Kilimanjaro in Tanzania.

The grey duiker was originally regarded as a type of bush goat because of its appearance. That is why Grimm originally described it scientifically as a type of goat Capra sylvestra africana in 1686. Capra is the generic name for the goats. Domesticated goats were developed from the common wild goat Capra hircus of Sweden. When he developed his scientific classification system in the mid  1700s, the Swedish botanist Carolus Linnaeus renamed the grey duiker Capra grimmia in 1758. In 1837, Ogilby placed it in a new genus as Sylvicapra grimmia  when it was realised that the duikers were not goats but antelopes.

The grey duiker occurs throughout southern Africa and there are five subspecies in this subregion with Sylvicapra grimmia grimmia occurring along the south Cape coast and in the Western Cape, Sylvicapra grimmia caffra in north-eastern KwaZulu-Natal and the northern provinces, and Sylvicapra grimmia steinhardti in the Kalahari region of the Northern Cape, Botswana and Namibia.

In the grey duiker the adult ewe is heavier than the ram although they are both around 55 cm tall at the shoulder. The adult ram in Botswana has a mean weight of 18.7 kg (range: 15.3 to 21.2 kg) as opposed to 20.7 kg (range: 17.1 to 25.4 kg) in the ewe. Because of its wide geographical range, the coat colour varies considerably from grey-brown in KwaZulu-Natal to reddish-yellow in the more northern parts of Africa. There is a characteristic wide black band along the muzzle from the eyes to the nose. The belly is white and the short, thin tail has a black tuft of hair. Only the ram has horns which are short and straight with only the lower part having ridges. Depending on the region of occurrence, 0.6 to 12.7 percent of the ewes can also carry vestigial horns. The grey duiker has pedal, inguinal and preorbital glands that are used in scent-marking. The preorbital glands are conspicuous as they occur in two black patches just below the lower corners of the eyes.

The habitat of the grey duiker marginally includes grasslands but it mainly consists of open to closed woodlands such as are found on Shayamanzi. Grey duikers can often be found in the ecotones (ecological intergradation zones) between two vegetation types such as riverine bush and bushveld or grassland and bushveld. The diet consists of 83 percent browse, 12 percent grasses and 5 percent wild fruits which makes the grey duiker a mixed feeder. When it browses it is a concentrate browser and the woody plants are cropped as high as 45 cm above the ground. Young grass sprouts are especially eaten after veld fires and under exceptional circumstances the grey duiker eats insects, lizards and smaller birds such as nestlings and may also feed on larger carcasses in the field.

The seeds of especially the sweet thorn tree Acacia karoo and the bushveld gardenia Gardenia volkenssii are distributed by grey duikers in their dung, while those of the kudu berry Pseudolachnostylis maprounifolia and the marula tree Sclerocarya birrea are regurgitated. In the Kalahari the grey duiker feeds on the flesh and seeds of the tsamma melon Citrullus lanatus which has a moisture content of 90 percent. The grey duiker has the most rapid through flow rate of food of all the African antelopes, which explains its wide geographical distribution. It is, for example, twice that of the greater kudu Tragelaphus strepsiceros which also mainly browses. A grey duiker eats some 348 g of plant material per day on a dry basis or 1.4 kg per day on a wet basis. Although it is independent of surface water, it will drink 0.5 to 1 litres of water per day when water is available. In doing so, it prefers natural or natural-looking waterholes.

The ram becomes sexually mature at an age of 12 to 16 months and the ewe when she is 9 to 12 months old, the latter the age when mating first occurs. A grey duiker is a solitary animal and a ram will mate with two or more ewes on ranges that are adjacent to his. The ram visits the ewe in her range for two to four days when she is in oestrus. Mating and births occur throughout the year without any peaks of occurrence. A single lamb of 1.4 to 1.9 kg is born in isolation in thick vegetation after a gestation period of 195 to 202 days. It remains hidden for up to three weeks but it can be active within 24 hours of birth. Up to 97 percent of all the adult ewes in a population will give birth during a given year. The ewe has four inguinal mammae. The lamb weans when it is three to four months old and grows rapidly to reach its weight as an adult when it is six months old. A grey duiker population in the wild normally grows at a rate of 20 percent per year and the life expectancy of a grey duiker in the wild is 15 years. However, in captivity it can be as long as 26 years.

Grey duikers are solitary animals, each staying within its own range. The ram has a territory that varies from 1.9 ha in the thickets of the Eastern Cape to 21 ha in the bushveld of KwaZulu-Natal. The range of an ewe is somewhat larger than the territory of a ram and she sometimes may be accompanied by her most recent lamb. Territory and range sizes depend on the quantity and quality of the food resources. Adjacent ranges of ewes may also overlap.

The grey duiker is active for most of the day and until around midnight. It then rests until around 04:00 before becoming active again. In areas where they are disturbed, grey duikers become totally active at night. Latrines and scent-marked objects are visited repeatedly and they mark fixed escape routes with the secretions of their pedal glands. Ranges that become vacant are soon occupied by young, dispersing animals.

The main grey duiker mortality agents in South-Africa are the lion Panthera leo, leopard Panthera pardus, black-backed jackal Canis mesomelas, side-striped jackal Canis adustus, honey badger Mellivora capensis, baboon hamadryas, serval Leptailurus serval, caracal Caracal caracal, python Python natalensis, and large birds of prey such as eagles and owls.

References:

Grubb, P 1999. Types and type localities of ungulates named from southern Africa. Koedoe 42(2): 13 - 45.

Grubb, P 2005. Order Artiodactyla. In D E Wilson and D M Reeder (eds), 2005. Mammal species of the world: a taxonomic and geographic reference, third edition. Baltimore: The Johns Hopkins University Press, pp 701 and 716.

Pfitzer, S and L Colenbrander 2005. The duikers. In J du P Bothma and N van Rooyen (eds), Intensive wildlife production in southern Africa. Pretoria: Van Schaik, pp. 230 - 232.

Skinner, J D and C T Chimimba (eds) 2005. The mammals of the southern African subregion, third edition. Cambridge: Cambridge University Press, pp. 672 - 675.

Article by Prof J du P Bothma

 

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