Sub-adult males and bulls spray-urinated when walking from one station to the other and especially when bulls were courting females. Bulls spray-urinate more often when courting females than when engaged in other activities. Also when courting, male A was twice observed scraping dung piles very vigorously using both hind legs and horns. It seems these activities have some social role within the species.
Owen-Smith (1974) found white rhinoceros bulls to be territorial, although they foray outside their territories to look for water in the dry season. Territorial borders are marked by large hollowed-out dung piles. Ritualized urination is most pronounced when bulls are patrolling the border regions. Subordinate bulls reside in these territories and use the same dung piles as the territorial bulls but they neither scatter their dung nor spray-urinate. The interpretation of results obtained from field studies as to whether the black rhinoceros occupy home ranges or territories are controversial. Goddard (1967), working in Ngorongoro Crater, found that home ranges of the black rhinoceros overlap extensively, with no evidence of territoriality. Klingel & Klingel (1966), working on the same rhino population, suggested that males may establish true territories because bulls stayed within well-defined home areas from which they never dispersed. Schenkel & Schenkel-Hullinger (1969) concluded from studies in Tsavo East National Park-Kenya, that the black rhinoceros was not territorial, whereas Frame (1980), in a brief study of black rhinoceros on the Serengeti Plains, concluded that '. . . the overlap in home ranges of males and tolerance between others suggest that the rhinos could have a territorial system similar to that described for the white rhinoceros'. Unfortunately the situation in the Crater at the time of the study did not offer a good opportunity for the study of territoriality, mainly because only male A inhabited the floor permanently after males E and F were killed at Seneto Plain. The other three males (B, C & D) were non-residents and rarely came onto the floor. Male A's core area is the Lerai-Gorigor region, which is the best rhino habitat in the Crater and where most females reside. The fact that the Crater wall males do not enter this area possibly indicates that male A is dominant. Contact between males was seen only once when male B from the Crater wall, on his way to Mandusi swamp, met males E and F at Seneto Plain and chased each one separately for 0.5 km or so. Otherwise, each male (except A) restricted his movements to within their own range. Male A patrolled two-thirds of the Crater floor and was occasionally seen in the ranges of males B and C probably looking for females. Encounters with these males were not observed. Space utilization by females shows a clearer pattern. They occupied ranges which overlapped extensively. No physical conflicts were observed between them and whenever they met, they greeted each other before parting peacefully (Kiwia, 1983).
study 1981-1982. During the present study, two males (E & F) and two females (G & P) were killed by poachers.
The ranging pattern of the resident black rhinoceros (Diceros bicornis) in Ngorongoro Crater (Fig. 1), was first studied by Goddard (1967) during the period 1964-1966.At that time there were seventy-eight resident rhinos on the Craterfloor. During the pre
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 - End
Habitat quality The distribution of food, water and shelter also determines range sizes. At the Lerai-Gorigor area where the three resources are close together, the resident rhinos have much smaller ranges compared to the Seneto Plain rhinos, where resources are more widely spaced. This was also found to be the case with the Masai-Mara rhino population (Mukinya, 1973). The higher values for seasonal range overlap of the Lerai-Gorigor rhinos indicate that they were more sedentary than those of Seneto Plain. The probable reason is that food was available at the Lerai-Gorigor area throughout the year. The Seneto rhinos on the other hand moved to the Lerai-Gorigor area during the dry season, presumably to seek food and water.
Individual rhinos were identified using methods described by Klingel & Klingel (1966), Goddard (1966) and Mukinya (1973, 1976). Individuals were classified as adults, sub-adults or calves to accord with the technique used by Goddard (1967).
