Steenbok

Raphicerus campestris (Thunberg, 1811)

Photo: Doug Lee

IUCN Conservation Status:

Survival threat rating: Lower Risk, least concerned (LR/lc)

This graceful buck has the misfortune to be named after a brick, perhaps because of its colour, and is the symbol of cleanliness among the African people. It has the second widest distribution of African antelope due to its ability to survive in marginal areas where larger, faster and more aggressive ungulates have disappeared following human pressure. In addition, its ability to feed almost exclusively on forbs in otherwise totally degraded and overgrazed habitat contributes significantly to its survival.

Taxonomy

Classification

The genus includes three species and two subspecies namely:

• Raphicerus campestris, the steenbok
• Raphicerus melanotis, the Cape grysbok
• Raphicerus sharpei sharpei, Sharp’s grysbok
• Raphicerus sharpei colonicus, the tropical grysbok

Former authors have recognised 12 sub-species of steenbok these being Raphicerus campestris bourguii, R.c. cunenensis, R.c. hoamibensis, R.c. horstockii, R.c. kelleni, R.c. natalensis, R.c. neumanni, R.c. steinhardti, R.c. stigmatus, R.c. tragulus, R.c. ugabensis and R.c. zukowskyi. Only six of these occur in the southern African sub-region. Taxonomic revision of the different sub-species is long overdue as there are only minute distinguishable differences between them.

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Description

It is a small gracious antelope with relatively long legs and a slender body. The skin is smooth, pale red-brown on the back and the belly and inner thighs a contrasting bright white. A darker brown, Y-shaped marking can sometimes be seen on the forehead. Ewes have four teats. Adult body size is reached within 14 to 20 months of age.

Comparison To Man

Trophy

Only rams bear fully developed horns. These are simple, straight and spaced widely apart. The tips are incredibly sharp and slightly bended forward. Most of the length is smooth except for two or three rings directly above the base. Ewes with deformed and inferior horns do occur.

Habitat requirement

Open and gently undulating plains with scattered trees and shrubs and a short to medium height (2-12 cm) grass layer of sweet, palatable, highly digestible grass species are favoured. Sourveld is completely avoided. The most suitable veld types occur within semi-arid savannahs, succulent Karoo and grasslands. The steenbok usually avoids rocky slopes, steep mountains, rugged country, sand-deserts, thickets and forests. Climatic conditions can vary from semi-arid (less than 200 mm annual rainfall) in the Kalahari, to sub-tropical (500-1 200 mm rainfall), with extreme temperatures of -10 degrees C to 50 degrees C. Patches of tall grass and scattered shrubs should be available as cover for protection. Disturbed areas such as roadsides, firebreaks, landing strips, the edges of cultivated lands and overgrazed patches are mostly favoured due to the abundance of pioneer, broadleaf forbs. Steenbok are totally independent of drinking water.

Optimum vegetation structure is the following canopy foliage cover:

• 40-80% cover between a height of 0 and15 cm
• 20-30% cover between 15 and 30 cm
• 15% cover between 30 and 45 cm
• 5% cover between 45 and 75 cm
• <5% cover above 75 cm.

Distribution

Feeding & Nutrition

The steenbok is a ruminant and a mixed feeder of both broadleaf forbs and short sweet palatable grasses of less than 12 cm that are low in fibre content. In the Kruger National Park its diet consists of 155 dicot forb species, 42 tree and shrub species, 15 creeper species and 20 grass species. It is a highly selective concentrate feeder with a definite preference for specific, most delicate, parts of plants. The feeding behaviour is dictated to by a high metabolic rate which requires a high protein and soluble carbohydrate intake. In general the diet consists 67% of dicot forb browse, 19% tree and shrub browse and 6% creeper browse and only 8% grass. However, studies on captive animals indicate that they prefer to browse exclusively, although in some habitats grass can form up to 50% of the diet. Steenbok are also known to dig for underground bulbs and succulent roots, especially in semi-arid environments. They drop down on the knees to feed at ground level and are strongly attracted to new growth on recently burnt veld. The mean feeding height for the steenbok is 21 cm, ranging from 0-53 cm. They are diurnal and remain active until 2-3 hours after sunset when they lie down under thicket, in tall grass patches or in old aardvark burrows. On moonlight nights feeding may extend later into the dark. Growing human disturbance has caused them to become increasingly nocturnal.

Social structure

Steenbok are mostly solitary or occur in male/female or mother/lamb pairs. They are strictly territorial, with the adult ram and ewe each having a separate, fixed territory. Frequent sightings of the same individuals in pairs in the same vicinity are a result of temporary meetings when individuals pass through the overlaps of adjacent home ranges. Such incidents can last up to three days and are frequently repeated. Pairs frequently form between the same individuals but only for courtship and mating purposes or as a mother with her lamb The common rapid development of horns in male lambs also contributes to the misconception of pair-bonding, as the ewe is seen in close association with her son for an extended period giving a false impression of adult pair-bonding.

Information Table

Bibliography