 Reference Base  Observations on two introduced black rhinos in Liwonde Na... |
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Bhima, R.; Dudley, C.O., 1996. Observations on two introduced black rhinos in Liwonde National Park, Malawi. Pachyderm 21: 46-54, figs. 1-3, tables 1-2
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| Location: |
Africa - Southern Africa - Malawi |
| Subject: |
Ecology - Food |
| Species: |
Black Rhino |
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Reintroduced Diceros bicornis in Malawi. Vegetation mapping at Liwonde NP
After identifying the sanctuary site, the area was fenced off and bomas were constructed in readiness for the rhinos. The sanctuary site was located from aerial photographs taken in May 1981 at a scale of 1:25,000. Units of vegetation which appeared to be homogenous from the photographs were marked and mapped and their area was estimated. Each unit was then checked on the ground in terms of its general structure and flora.
Plant species eaten by the rhinos
The plant species eaten by the rhinos were recorded by observing the rhinos feeding while they were in the bomas, and by checking for damage of the plants along the rhino tracks after their release into the sanctuary. Rhino browse characteristics are quite distinctive and are unlikely to be confused with other browser signs in the sanctuary, such as those of the kudu or impala.
Feeding observations were also divided into threemonthly records in order to detect plant species eaten throughout the year as well as seasonal differences.
Plant species eaten
There are 40 species of woody plants from 18 families which have so far been selected by the rhinos, as listed in Table 2. Woody species which were eaten throughout the year were A. nigrescens, A. sp., C. mopane, Combretum fragrans, E. ingens and Ziziphus mucronata. In the drier half of the year, D. melanoxylon was eaten in large quantities.
Table 2. Plant species eaten by rhinos in the sanctuary during their first year in Liwonde, in four periods: January to March (J-M), April to June (A-J), July to September (J-S) and October to December (O-D). The list for J-M includes plants which were eaten in the Liwonde bomas.
Plant species eaten Period of year
J-M A-J J-S O-D
Annonaceae
Anisotes formosissimus +
Cleistochlamys kirkii + +
Friesodielsia obovata +
Asclepiadaceae
Fockea Multiflora +
Apolynaceae
Stophanthus nicholsonii +
Burseraceae
Commiphora africana +
Caesalpinoideae
Cassia abbreviala +
Colophosospermum mopane + + + +
Capparanceae
Capparis tomentosa +
Thilachium africanum +
Combretaceae
Combretum apiculatum +
Combretum fragrans + + + +
Combretum imberbe + +
Combretum mossambicense +
Terminalia stenostachya +
Euphorbiaceae
Croton gratissimus +
Croton megalobotrys + +
Euphorphia ingens + + + +
Phyllanthus reticulatus +
Malvaceae
Azanza garckeana + +
Mimosaceae
Acacoa sp. + + + +
Acacia nigrescens + + + +
Acacia polyacantha +
Acacia xanthophloea +
Albizia anthemintica +
Fabaceae
Dalbergia boehmii +
Dalbergia melanoxylon + +
Lonchocarpus capassa +
Melletia usaramensis +
Pericopsis angolensis + +
Rhamnaccae
Ziziphus mucronata + + + +
Rubiaceace
Canthium frangula +
Crossopteryx febrifuga +
Xeromphis obovata +
Salvadoraceae
Salvadora persica +
Sapindaceae
Lecaniodiscus fraxinifolius +
Solanacae
Solanum incanum +
Tiliaceae
Grewia bicolor +
Grewia monticola +
Grewia stolzii +
Discussion
Although 40 species of plants are listed as being eaten by the rhinos, the number will probably increase substantially, particularly when herbacious species are recorded and when observations intensify. Smithers (1983) stated that over 200 plant species are eaten by the black rhino, while Goddard (1970) recorded 102 species eaten in Tsavo National Park, Kenya. However, Emslie & Adcock (1994) found that only a few woody species (about ten) account for the bulk of black rhino's diet. In Liwonde, six 'key' species were utilised throughout the year, namely C. mopane, Acacia nigrescens, A. sp., E. ingens, C. fragrans and Z mucronata
Emslie & Adcock (1994) noted that plants with a high moisture content, such as leguminous plants and species in the Euphorbiaceae family, are important dietary items for black rhinos. Both Goddard (1968) and Loutit et al (1987) specified that the Euphorbia was an important food item and that Euphorbia species, along with other succulent plant species, provide rhinos with water in the absence of free water. These findings seem consistent with those of the Liwonde sanctuary study from which it was noted that ten leguminous species, four Euphorbia species and one species each from the Asclepiadaceac and Apolynaceae families, were among the list of browsed species.
We believe that E. ingens played an important role in providing moisture during the late dry season in 1994. This woody plant is filled with a white latex fluid which is toxic to some animals but does not seem to harm the rhino. The rhinos began to feed on the E ingens very soon after their release from the boma and have caused major destruction of the species over the last 16 months. In the western half of the sanctuary, where E. ingens is very common, all the E. ingens less than 17cm in diameter in the monitoring plots have been destroyed. The feeding is wasteful, as the rhinos usually push the plants over and feed on the stems lying on the ground. Plants over 20 cm in basal diameter are probably safe from being pushed over. There was a noticeable increase in the amount of woody parts from Euphorbia species found in rhino dung in the late dry season.
Fockea multiflora, a large, latex-filled liana, also showed signs of being fed upon heavily as the dry season progressed in 1994. Some of these plants have had most of their basal stems eaten away by rhinos. However, none of them has died so far due to damage. Hall-Martin et al. (1982) reported that F. edulis was eaten by rhinos in Addo National Park, South Africa.
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