 Reference Base  Ranging patterns of the black rhinoceros ( Diceros bicorn... |
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Kiwia, H.D., 1989. Ranging patterns of the black rhinoceros ( Diceros bicornis (L.)) in Ngorongoro Crater, Tanzania. African Journal of Ecology 27: 305-312, figs. 1-3, tables 1-3
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| Location: |
Africa - Eastern Africa - Tanzania |
| Subject: |
Ecology - Population |
| Species: |
Black Rhino |
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Data for range size determination were collected concurrently with those for other studies (Kiwia, 1983) and not systematically. Location points for nine resident rhinos of different sex and age classes were plotted on 1:50,000 maps with grids of 1 x 1 cm, each equivalent to an area of 0.25 km 2 . The Crater floor is flat and open so that it was fairly easy to pinpoint the locations of the rhinos on the maps. The 'Minimum Area Method' (Hamilton, 1976) was used to determine range sizes. An area was calculated from a polygon obtained from connecting the peripheral location points of each individual. Wet (January-June) and dry (July-December) season location points were marked differently so that seasonal ranges could be calculated and the extent to which these ranges overlapped could be determined. Annual ranges were calculated from the polygon obtained by connecting all peripheral location points of each individual, regardless of the season.
Results
Adult male A occupied the largest annual range (69.0 km? ) in the Crater, followed by the females and sub-adults in that order (Table 1), but the sample size was too small for any differences in range size to be tested statistically. Wet season ranges for most individuals appear to be larger than the dry season ranges (Table 1), but the difference was not significant (Wilcoxon matched pair signed-rank test t= 19, n=9, P < 0.05).
Seasonal ranges for the nine individuals overlapped extensively by values ranging from 46 to 100 %. Apart from males E and F, which were seen together most of the time, male annual ranges overlapped only slightly and any overlap was due to occasional forays by male A. Female annual ranges overlapped with those of other females by 27-100% and ranges for males and females overlapped by 67-100% (Table 2).
Table 1. Annual and seasonal range sizes ( km?) and seasonal range overlaps (%) of nine resident rhinos in Ngorongoro Crater (January 1981 to May 1982).
Adult male range Adult female range Subadult
A E & F G H I J K & L M N
Annual Range 69.0 - 27.8 33.0 12.5 20.8 47.3 22.8 25.
Wet season range
(Jan-June) 43.0 26.0 26.0 31.8 9.8 19.8 28.5 21.5 22.
Dry season range
(July-Dec) 59.6 - 18.0 16.6 11.8 14.0 41.3 14.0 21.8
Seasonal range
overlaps (%) 74.0 - 80.0 61.0 84.0 76.0 46.0 76.0 84.
Kiwia 1989b
Table 3. Comparison of mean annual-range size ( km? ) of black rhinoceros in Ngorongoro Crater during 1964-1966 (Goddard 1967) and 1981-1982 (this study)
Sex/age class 1964-1966 1981-1982
n mean range n mean range
Adult males 16 15.8 2.6-44.0 1 69.0 -
Adult females 13 15.0 2.6-26.2 6 31.5 12.5-47.3
Subadult males 2 36.0 13.9-58.0 1 22.8 -
Subadult females 7 27.7 14.2-58.0 1 25.0 -
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