 Reference Base  Habitat preference of the white rhino in the Kruger Natio... |
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Pienaar, D.J., 1994. Habitat preference of the white rhino in the Kruger National Park: pp. 59-64, figs. 1-2
 | In: Penzhorn, B.L. et al. Proceedings of a symposium on rhinos as game ranch animals. Onderstepoort, Republic of South Africa, 9-10 September 1994: pp. i-iv, 1-242 |
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| Location: |
Africa - Southern Africa - South Africa |
| Subject: |
Ecology - Habitat |
| Species: |
White Rhino |
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Kruger NP. A study was begun in 1988 to ascertain the landscape and habitat preferences and dispersal of the white rhinoceros in the KNP. The objective of this study was to ascertain which landscapes in the KNP white rhino select for and why they selected them.
Methods
Details of the methods used to establish white rhinoceros landscape preference in the KNP have been described by Pienaar et al. but will be briefly outlined below.
A preference index was used to get a perception of the ratio of habitat use to habitat availability. A chi-square test was then performed to test for the goodness-of-fit of utilized habitat to available habitat types. The null hypotheses tested by the chi-square test was:
H01: Usage occurs in proportion to availability, considering all habitats simultaneously, with the option of testing
H02: Usage occurs in proportion to availability, considering each habitat separately.
When the chi-square test detects a significant difference in usage versus availability, a Bonferroni z-statistic is used to construct confidence intervals based on the proportion of time an animal uses each habitat type, in order to determine which habitat types are used more or less than expected. The landscape preference was determined for the summed aerial count data from 1979 to 1991.
Fifteen white rhinoceroses were tracked using radio telemetry to ascertain their activities and habitat use. The immobilization and collaring procedures are explained by Pienaar & Hall-Martin. All rhinoceroses fitted with transmitters occurred in areas of high white rhinoceros density (>0,5 per km?). These high density areas were mapped using the aerial census data which are collected annually in the KNP. The collared rhinoceroses were regularly tracked and observed on foot and all the locations were mapped on 1:50 000 topographic maps.
When the animals were located, data for the following variables were recorded: time, number of animals, activity, landscape type, habitat type, grass cover, air temperature, grass height and composition and the structure of the woody vegetation. A Canonical Discriminant Analysis was performed to determine canonical variables (linear combinations of the quantitative environmental variables) that best summarised variation between activity classes.
Landscape preference
The southern KNP is zoned into nine landscapes. A landscape is an area with a specific geomorphology, macroclimate, soil and vegetation pattern and associated fauna.
In the present study the moderately undulating granitoid plains with Combretum woodland, is clearly the most preferred landscape of the white rhinoceros in the southern KNP on a long-term basis. It is also the principal landscape according to white rhinoceros distribution. The Combretum woodland landscape has an undulating topography with distinct bottomiands where accumulation of clay and minerals take place. The low shrub stratum is open and the field layer is moderate to dense and usually less than 1 m in height. Field observations have shown that in the mornings white rhinoceros feed by preference on the shade-loving grasses such as Panicum maximum that grow on the riverbanks. When it gets warm they utilize the watersheds to rest in the shade. White rhinoceroses are also very partial to wallowing in the mud-holes that form on the clayey soil on the bottom-lands. It seems thus that the Combretum woodland landscapes fulfil most of the white rhinoceros's needs.
Landscapes avoided by the white rhinoceros on the long term were the granitoid mountain bushveld and the granitoid lowland Acacia thickets.
The granitoid lowland Acacia thickets landscape is the largest landscape in the southern Kruger National Park but the white rhino density is low. This landscape is characterised by a dense woody vegetation with a particularly dense low shrub stratum. The grass layer in this landscape is sparse. Field observations have shown that white rhinoceros are not partial to areas with a dense low shrub stratum such as occurring in this landscape. The more open, brackish areas along riverbanks are the only areas used to some extent by white rhinoceroses. Other landscapes such as the Karoo Sediment plains with Acacia welwitschii thickets, also have a dense woody vegetation but the low shrub stratum is open, and hence white rhinoceros do not avoid those landscape.
The granitoid mountain bushveld landscape is characterised by steep slopes with shallow leached soils and bush-savanna vegetation. The avoidance by white rhino is probably related to poor grass quality, a species composition that consists mainly of unpalatable grasses as well as to the topography.
Water Requirements
White rhinos are dependant on regular access to surface water and will drink daily or twice daily during the wet season when water is abundantly available.
Diet composition
White rhino are selective grazers; no browsing was observed in the KNP or in the Umfolozi Game Reserve. Forbs were also avoided and white rhino even avoided favoured grass patches that contained plenty of forbs.
Habitat use
The catenary sequence (Figure 2) in the Combretum landscapes in the KNP affects the habits of white rhino. During the early morning white rhino typically feed on the bottomlands, riverbanks and brackish areas adjacent to the water courses. The soils on the footslopes and valley bottom have a high clay component and small pans form here during the rainy season. White rhino are very fond of wallowing or lying in these pans.
Structure of the woody vegetation
The structure of the woody vegetation plays an important role in the habitat choice of white rhino. Very open plains with sparse tree cover are not good white rhino habitat. Such areas do not have adequate shade for the animals to rest in. Conversely, areas with a very dense low shrub strata (< 2m) are also not favoured by white rhino. White rhino have a broad, sensitive upper lip that they use to pluck grass off and where the low shrub strata is dense they can not get to the grass. Knee high shrubs that grow between the grass also inhibit their feeding activities.
The most favoured woody vegetation structure consists of an open low shrub (< 2m) stratum, and a moderate high shrub (2-4m) and tree (>4m) strata. Habitats with such a woody vegetation structure usually contain a moderate to dense grass cover with a high proportion of palatable grass species. These features are consistent with the drier types of woodland savanna.
Discussion
The relocation of white rhino should be approached with caution as they are very specific in their habitat requirements. The recipient area should be inspected beforehand to assess if the necessary habitat is available. White rhino relocation to areas outside their historical distribution should be cautiously considered before implementation. The distribution of white rhino in the west of their historic range seems to coincide with the 400 mm rainfall isohyet. Consequently, white rhino should not be moved to areas where annual rainfall is less than 400 mm. White rhino are dependant on regular access to surface water although they can go for 3 days without drinking. The occurrence of mud wallows will increase the appeal of an area for white rhino. White rhino select for the more palatable grasses when grazing and they will not prosper in sour grassveld areas. The structure of the woody vegetation is very important in deciding if an area is suitable for white rhino. White rhino will avoid areas if the low shrub (< 2m) stratum is very thick or if the habitat consists of open plains with no shade. Similarly will mountainous areas with poor, leached soils not be suitable white rhino habitat.
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