Ecology and behaviour of the black rhinoceros diceros bicornis linn. 1758 in Masai Mara game reserve
The ecology and behaviour of maasai Mara Game Reserve rhinoceros was studied from May 1971 to August 1972. At the end of August 1972, the entire Mara rhino population consisted of 10 animals of which 73% were adults and 27% were immature animals which accompanied their mothers. The adult population consisted of 54% males and 46% females. The density of black rhino in the Mara Game reserve is 0.07/km2 considering the entire reserve area (1530 km2) and 0.14/km2 considering the area occupied by rhinos 2 (749 km). The recorded highest individual distribution area density was 0.?3/km2. There was no noticeable difference between the mean densities obtained from the ground and aerial count though an aerial count was not carried out in the Triangle area. In the entire study area, 13 rhino distribution areas were known. Bach of the 13 distribution areas had rhinos which associated with each other but individuals from one distribution area were never observed associating with individuals from another distribution area. The movement of rhinos out of the reserve was negligible. Rhinos were distributed over the plains, grassland with scattered trees, slopes of hills and thickets along river courses. Rhinos appeared to prefer areas with abundant cover for shelter, food, water, and with absence of human and domestic animals. The sex ratio of adult females: adult males was 1:1.1 and for immature females: immature males was 1:3.2. Out of 28 immature rhinos 11 were not sexed due to some difficulties hence the sex ratio for immature rhinos cannot be interpreted with confidence. The entire rhino population was divided into four age classes. Age class I representing individual rhinos from 0 - 1 year old, class II from 1 - 2 years old, class III from 2 - 4 years old and class IV over 4 years old. Although rhinos are known to mate at any time of the year, individuals of the Mara population were observed mating during the period between September and April. Usually, this is the hot period of the year. Mortality of adults and calves as found to be very low. Only one adult rhino died during the study period and none of the calves died. On social organization, black rhinos are solitary animals but occasionally, adult males and adult females can be observed together particularly during the feed.ing hours or during mating periods. Sub-adult rhinos are solitary but they can sometimes be seen joining their mother and in the case of females, joining adult males. The only form of organization which is rather permanent is mother-calf unit which is frequently observed until the time when calf leaves the mother. On some occasions mother-calf unit is observed associated with single adult male. rhino's pattern of association strengthens bond between mother and its calf and weakens the bond between adult individual rhinos. Group defence from enemies is minimal and individual rhino is left to defend itself alone. This pattern of association, on the other hand, makes it difficult to locate rhinos in the wilderness other than the times when they are on open areas carrying out their other daily activities. Rhinos have home ranges which are generally shared by males or females in the adjacent home range. The size of home range is dependent on available food, cover, ater, main activities and domesticated animals. The home range size varied with social units. Females with calves had lar cr home ranges than single females or single males. Females ith calves move a lot looking for palatable herbs and shrubs. movements of rhinos within their home ranges, either daily or seasonal, causes a considerable degree of home range overlapping. No indication of territorial behaviour was observed. Because rhino tend to remain attached to some particular area, the density can be quite hi h in some areas and less in other areas depending on the number of individual rhinos occupying these areas. In the game reserves or national parks the rhino attachment to particular areas makes it possible for ran ers to have a rough estimate of areas to the tourists. Also this attachment to particular area limits the degree of association with other rhinos other than its neighbours. Rhinos were also observed association ith the buffalo, giraffe, topi and wildebeest living within rhinos home ranges. Black rhino in Mara were observed feeding on varieties of plants with preference for Solanum incanum and Acacia species. About 70 different plants species ; from 30 different botanical families ere recorded. During the rainy periods a variety of palatable herb are easily available and it is during these periods that rhinos were observed selecting a wide variety of herbs and shrubs. However, during the dry period most of the herbs and shrubs dry up and climax of shortage of food is observed during the burning period which normally occurs during the dry period. It was observed that rhino's pattern of food selection is dependent partly on relative density and relative frequency of plant species used. Rhinos were observed feeding mainly in open grass and scrub with scattered trees habitats. These two habitats mainly carry most of rhino's food. Rhinos in Mara were observed to feed mainly on regenerating vegetation. Branches with leaves, and branches with leaves and inflorescences were mainly eaten. A portion of plant ranging from 7 to 26 cm is mostly swallowed by rhino. In some cases leafless remnants of plants were found uprooted. Observations indicated two feeding peaks within twelve hours'of the daylight. One feeding peak is in the morning and the other in the afternoon. However, other minor activities may be observed during the feeding peaks. here i no competition for food ith other animals. ~ild animals using the sa e plants used by rhinos have different feeding levels. Rhinos in Mara were observed to be mainly group~ feeders. Rhinos were observed to visit salt licks in distribution area A. Other animal species like topi and buffalo were also observed in this salt lick places. Salt lick places contained odium, magnesium, potassium and calcium. Rhinos were observed drinking water mainly from sunset or just after the sunset. Ho ever, there is no doubt that they also drink early in morning or spend most of their night time near the water places because they were mostly located in the morning near the water places walking to their feeding rounds. mating was observed mainly during the period from September to April. However, though no record was made, rhino can mate at any time of the year. allowing is mainly limited to the rainwater pans or standing water along the seasonal streams or rivers. alloing takes place during mid-day which is normally the hot part of the day. However, wallowing activities ere frequently observed during the wet days rather than during dry periods. This is probably due to availability of water in the rainwater pans. After alloin~ rhinos were observed rubbin their bodies against a tree, tree branch or termite mound. Rhino maintain dung piles. Some of the dung piles are along tracks frequently used by the rhinos to the water places or to feeding areas. Over 90% of dung observed was scraped. Dung piles were aleo observed being shared and tne"degree of sharing dun piles may depend on how often the part of the home range where the dung piles are located is used by another rhino. rhinos have no definite urinals and were not observed defecating and urinating simultaneously. rhinos normally walk as observed during the feeding hours. However, when disturbed they can run at a speed of 60 km/h. Then running females with calves are followed closely behind by their calves but sometimes, though rarely, calves can be observed leading their mothers into sheltering places. Rhinos were observed resting during the mid-day if they were not wallowing. Rhinos were observed lying down under a tree shade or resting while standing next to a tree which provided shade. Rhinos reaction to strangers reveal that a rather small number of tendencies are involved in varying proportions. These tendenciea are curiosity, fear, anger and inertia. A number of other lines of possible res arch are suggested.