 Reference Base  The mammals of the southern African subregion, new edition |
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| Location: |
Africa - Southern Africa - South Africa |
| Subject: |
Ecology - Food |
| Species: |
Black Rhino |
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South Africa. In both Hluhluwe and Umfolozi Acacia spp or their close relatives comprised at least half of the 10 most preferred species, and as they grew in size they became less and less preferred (Emslie & Adcock, 1990b). The most preferred species were A. gerrardii, A. senegal and A. borleae. The more common A. karroo and Dichrostachys cinerea were less preferred, but more important in the diet, accounting for about a fifth of woody browse eaten in summer.
Despite the different species composition of the Umfolozi and Hluhluwe study areas, the striking feature of the black rhinoceros feeding was the very similar contribution to the diet by a number of important species that occurred in both areas (Table 296.1).
Table 296.1
Percentage contribution of the top 10 woody species in the woody diet of black rhinoceros, D. bicornis, in the Hluhluwe and Umfolozi Game Reserves (Emslie & Adcock, 1990b)
Hluhluwe Umfolozi
*Spirostachys africana 22,5 24,1
Acalypha glabrata 13,9
*Dichrostachys cinerea 10,8 10,5
*Acacia karroo 8,2 10,3
Berchemia zeyheri 6,1
Acacia caffra 5,2
*Acacia nilotica 3,8 4,7
*Acacia gerrardii 3,6 5,1
Hibiscus spp 3,4
*Maytenus nemorosa 3,2 3,1
Acacia borleae 5,4
Ehretia rigida 4,3
Acacia tortilis 4,3
Schotia capitata 2,9
Through browsing, rhinoceros prune the bushes on which they feed, so that they become rounded on the sides and top. The bushes show little sign of the breaking or tearing which characterises elephant feeding.
In Kaokoland, Namibia, of the 103 plant species encountered, rhinoceros utilise 74 (Loutit, Louw & Seely, 1987). Apart from expected species such as Acacia albida, Euphorbia virosa was also fed upon and this plant and Merrernic, spp had the highest water content. The high tannin content and other defence mechanisms such as formidable spines on E. viroso did not deter the rhinoceros from eating them, nor did the very high crude fibre content of Comrniphora virgato, Sterculia africana and Euphorbia darnarana. However, in deserts, food selection may be influenced by other factors than nutritional value. For example, in parts of East Africa. Euphorbia tirucalli forms 70% of their diet during the dry season (Goddard, 1968), the rhinoceros obtaining their moisture requirements in this way. This was also the case with D.b. michaeli in the Addo National Park where they selected succulent plants with a high moisture content in the dry season (Hall-Martin, Erasmus & Botha, 1982).
From studies undertaken in the Subregion, one can conclude that black rhinoceros feed on an unusually wide variety of species, and they are flexible, shifting their preferences according to availability of species. They can also utilise plants unavailable to other herbivores because of their formidable chemical and morphological defences.
In the Zambezi Valley, Zimbabwe in the 1982/83 and 1983/84 wet seasons, rainfall was only about half the mean over 17 years. This resulted in reduced vegetative growth and at least 38 rhinoceros died of malnutrition in the subsequent dry seasons. Most (22) of these animals were under 10 years of age, with the next biggest category (18) being those 31-40 years of age (Dunham, 1985). This indicates how important it is not to exceed carrying capacity with species such as rhinoceros which cannot be translocated rapidly from one area to another.
In the well-watered Hluhluwe Game Reserve, they drink nightly, as they do in the hot, dry months in the Etosha National Park, but in the cooler months they drink every second night (Owen-Smith, 1988).
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