 Reference Base  Black rhinoceros (Diceros bicornis (L.)): population size... |
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Kiwia, H.D., 1989. Black rhinoceros (Diceros bicornis (L.)): population size and structure in Ngorongoro Crater, Tanzania. African Journal of Ecology 27: 1-6, fig.1, tables 1-2
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| Location: |
Africa - Eastern Africa - Tanzania |
| Subject: |
Ecology - Census Methods |
| Species: |
Black Rhino |
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All individual black rhinoceros in the Crater were photographed at close range, on both sides, and identified using various morphological characteristics. The photographs of each individual were mounted on an index card, below which a detailed description of the individual was written. Some of the features used for identification were: sex (external genitalia), age class, horn structure, ear marks and permanent scars. The same method was used with success by Klingel & Klingel (1966), Goddard (1966), Mukinya (1973, 1976) and Frame (1980). The characteristics for horns proved very useful for identifying individuals in the field especially when they were at a distance or lying down.
Makacha, Mollel & Rwezaura (1979) compiled data to show the trend of the rhino population in the Crater since 1958. However, since three different census methods were included in the compilation (aerial, vehicle and individual recognition), the data should be interpreted with caution because possible biases were not allowed for. Goddard (1967b) and (Western 1982), for example, found that aerial counts consistently under-estimated the actual number of rhinos in an area. Single-day vehicle or foot count methods also underestimate the population size of rhinos in the Crater. Throughout the study period, rarely could more than ten individuals be located in a single day despite the fact that each rhino's locality in the field was roughly known to the observer. In fact, on some days no rhinos were seen. The Ngorongoro staff use vehicles once or twice a year to conduct total animal censuses in the Crater. In September 1981, I participated in one such census and not a single rhino was spotted by the five groups involved in the exercise. Thus, it seems likely that the best method for counting rhinos in any area is that of individual recognition. This method was feasible here because the Crater floor is relatively small with good visibility, the rhinos were relatively sedentary and few in number, and the observer had enough time to conduct the study.
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