It is generally acknowledged that the population of black rhino Diceros bicornis michaeli in what is now the Masai Mara National Reserve (the Reserve) during the mid-1900s probably numbered between 150-200 animals (Brett, 1995). However, as a result of poaching, the thinning of the Croton dichogamus thickets (that are such a characteristic feature of the Mara and northern Serengeti), and an appreciable increase in elephant numbers (Dublin, 1991), this figure has been greatly reduced. By 1972 there were known to be only 108 rhinos remaining in the Reserve (Mukinya, 1973). In the following decade poaching continued and by 1985 the population of rhinos had been reduced by over 80% to fewer than 13 animals (Brett, 1995). The status of the black rhino had reached crisis point in the Reserve. Within a span of 12 years rhino numbers have trebled to a healthy population of 40 animals. The increase has been due to improved surveillance and monitoring, the cessation of rhino poaching within the Reserve, the birth of 25 calves and the identification of four, hitherto unrecorded animals during the period of this study. In the mid-1900s, the Masai Mara had a justified reputation as being a haven for wildlife. Rhinos were reported to have occurred in relatively large numbers in suitable habitats throughout the Reserve. The majority were located in the Triangle area, some in the Keekorok area and a few in the Musiara area - in total, an estimated 150-200 animals (Jack Barrah, pers.comm.). However, in the 1960s, as a result of extensive poaching for rhino, combined with the destruction of the habitat by constant, uncontrolled, annual (and even biannual) bush fires and an exceptionally heavy influx of elephants seeking asylum in the Reserve (Dublin, 1991), rhino numbers declined appreciably. By 1972 only 49 % of the area was occupied by 108 rhinos in 13 separate distribution areas (Mukinya, 1973), as shown in Figure 2A as areas A to M. Persistent and extensive poaching during the following ten years resulted in the further removal of many of the remaining rhinos. This was most noticeable in the Triangle area west of the Mara River, the area between Sand River and the Kuka Hills where rhinos have been eliminated, and in the Musiara area where only a single animal remains. Only 30% of the Reserve is now occupied by 40 rhinos in five distribution areas (A-E), all of which are located east of the Mara River, as illustrated in Figure 2B. The present study indicates that the configuration of rhino home ranges and distribution areas have altered considerably over the past 20 years.
40
< 13
108
150-200
Mara & Serengeti - Diceros bicornis. Not only is the Mara Reserve an integral part of the Mara/ Serengeti ecosystem on account of the annual migration of about two million ungulates, but also due to the movement, throughout the year, of at least 15 rhino
The Reserve presently has five distinct rhino distribution areas (Table 1) comprised of closely overlapping individual home ranges of more than one rhino except for Musiara (E), with only one remaining animal. Currently 22 (55%) of the Reserve's 40 rhinos are resident in area A, which has always had a relatively large number of these animals. Mukinya (1973) also records this as being a heavily populated area with 31 (29%) of the 108 rhinos then resident in the Reserve. However, area A is the largest. In terms of density, area D supports the highest number of rhinos per km?, as seen in Table 1. Table 1 Individual distribution areas, numbers of rhinos and their relative densities in June 1995. Area Number % of total Distribution Number of of rhinos population area in km? rhino per km? A 22 55.0 181 0.12 B 7 17.5 118 0.06 C 4 10.0 58 0.07 D 6 15.0 16 0.38 E 1 2.5 86 0.01 Total 40 100.0 459 0.09 Excluding area of overlap 40 100.0 399 0.10 Overlap of distribution areas Although four of the five distribution areas presently overlap (Figure 2B), Mukinya (1973) recorded that overlaps only occurred with home ranges and not with distribution areas, and that the latter were clearly separated from each other (Figure 2A). At present there are three distinct distribution area overlaps totalling 60 km? or 16% of the total area occupied by rhinos east of the Mara River (12 km? in areas A-B, 38 km? in areas A-C, and 10 km? in areas B-D). It is possible that these overlaps allow the exchange of genes between members of adjacent distribution areas. Rhinos from geographically separate distribution areas were seen consorting in these overlaps on at least ten occasions between 1992 to 1995 but no mating was observed. In each instance, the rhinos involved had returned to their respective home ranges within two to four days. Density Mukinya ( 1973) records that the total area of the Reserve occupied by rhinos in 1972 was 749 km?, thereby giving a density of 0.14 rhino per km?. At present the total area occupied by rhinos is only 399 km?, with a density of 0.10 rhino per km? However, taking into account the 60 km? overlap of distribution (figure 2B), the total area occupied by rhinos is 459 km? with a corresponding density of 0.09 rhino per km?. Movement of rhinos into and out of the Reserve Not only is the Reserve an integral part of the Mara/ Serengeti ecosystem on account of the annual migration of about two million ungulates, but also due to the movement, throughout the year, of at least 15 rhinos (the majority being females with their calves) between the Mara and northern Serengeti. These movements are not without their dangers. Although the rhinos move from one protected area to another, they run the considerable risk of being poached by cattle raiders which infiltrate the Park and Reserve along the Serengeti/ Mara international boundary to steal Maasai livestock on the Reserve's western and eastern boundaries. There could also be the occasional movement of one or more rhinos between the Reserve and the Laleta Hills, four to five kilometres east of the Reserve. Two or three times each year, reports are received of rhinos being seen within the Maasai group ranches, up to eight kilometres north of the Reserve. These could be sub-adult animals from the Reserve trying to establish home ranges, or adults in search of mates.
There could also be the occasional movement of one or more rhinos between the Masai Mara Reserve and the Laleta Hills, four to five kilometres east of the Reserve. Two or three times each year, reports are received of rhinos being seen within the Maasai group ranches, up to eight kilometres north of the Reserve. These could be sub-adult animals from the Reserve trying to establish home ranges, or adults in search of mates.
Figure 4 illustrates the number of calves born between 1985 -1994 and shows that the mean number of calves born per annum over the past ten years is 2.4. Assuming that the population remains stable and that in average of 2.4 calves continue to be born each year it should be possible for the population to reach 50 rhinos by the year 2000.
Despite the accomplishments of FOC and the NCC over the past decade, there is no room for complacency. What has been gained in ten years could be lost overnight. The following recommendations are made in the long-term interests of rhino management within the Reserve. Fire management Uncontrolled, annual (and sometimes biannual), hot fires, are having a notable and deleterious effect on the remaining thicket and woodland habitat of the rhino, specifically with regard to food resources. Fire is not a new phenomenon for the Reserve for it has played an important role in the vegetation dynamics of the area over a long period (Dublin, 1991). If permitted to continue, uncontrolled fire will lead to the loss of even more valuable rhino habitat. The management authorities must decide now if the Reserve should remain a predominantly grassland habitat, which is what it is at present (and which is largely unsuitable for black rhino), or if fires should be managed and controlled, thereby maintaining and improving a mixed woodland and grassland habitat. Improved habitat management would cater both for the annual migration of grazers from the Serengeti and for the maintenance of the largest, free-ranging population of the black rhino in Kenya. The Reserve has had an approved fire management plan since 1993 but its implementation is now long overdue. This, together with a study of the impact of fire on rhino habitat, feeding patterns and browse availability, is a priority. Movement of rhinos between Masai Mara and the Serengeti Between 1992 and 1995 the standard of rhino surveillance and monitoring improved appreciably. An important outcome of this has been better knowledge of the individual rhinos and greater awareness of the extent of their movements back and forth between the Reserve and northern Serengeti. Rhinos require exceptionally close surveillance, monitoring and security. Although there is an anti stock-theft unit in the vicinity to monitor and combat cattle rustling and to help the security of visitors in the area, its duties do not officially include surveillance or security of the local rhino population. A dedicated ranger post should be placed at a strategic location along the Sand River, from here a minimum of six, suitably equipped rhino surveillance rangers can operate. In addition, some form of regular and joint Mara/Serengeti rhino surveillance and monitoring patrols should be undertaken along the Kenya/ Tanzania international boundary. Illegal encroachment of livestock Black rhinos are normally very shy of cattle and have had to abandon about 50 km? of two prime habitats in the Reserve, one immediately south of the Talek River, the other in the northern Ngama Hills. Continuous, illegal incursions into these two areas by hundreds of domestic livestock, which originate from neighbouring group ranches on the Reserve's northern boundary, are denying the rhinos two important habitat localities in the Keekorok area. The Reserve's new by-laws cater for the prosecution of illegal grazing and they should now be strongly enforced. Ranger training Since the inception of a ranger force specifically for rhino surveillance and monitoring, inadequate attention has been given to the practical and theoretical training of these men and their officers. A suitable in-service training programme similar to that of the Natal Parks Board (Sandwith, 1990), incorporating aspects of rhino biology and the status of the rhino as a highly valuable, endangered species is urgently required. After successfully completing such a programme, the rangers should not be withdrawn or replaced after only a few months of service as is frequently the case now. The long-term presence of motivated and well-disciplined personnel who have an extensive knowledge of the individual rhinos under their charge and a high degree of esprit de corps, is an essential component of an efficient rhino surveillance, monitoring and security programme.
In early 1980, in an attempt to halt the continued poaching and almost certain extinction of the species within the Reserve, a special rhino surveillance team was established and jointly administered by the Narok County Council (NCC), custodian of the Reserve, Friends of Conservation (FOC), then Friends of the Masai Mara, World Wide Fund for Nature, and the then Wildlife Conservation and Management Department of Kenya. Since 1983 the surveillance team has been administered solely by FOC in collaboration with NCC and their rangers.
In early 1980, in an attempt to halt the continued poaching and almost certain extinction of the species within the Reserve, a special rhino surveillance team was established and jointly administered by the Narok County Council (NCC), custodian of the Reserve, Friends of Conservation (FOC), then Friends of the Masai Mara, World Wide Fund for Nature, and the then Wildlife Conservation and Management Department of Kenya. Since 1983 the surveillance team has been administered solely by FOC in collaboration with NCC and their rangers.
Masai Mara. Diceros bicornis michaeli
Map of Maasai Mara in relation to Serengeti. Map of comparative distribution areas of black rhinos
The Reserve is centred on 1?30' S and 35?0' E in the Narok District of Kenya, approximately 200 km south-west of Nairobi. It covers an area of 1510 km? (Cumming et al., 1990). Altitude varies from 1450m ASL along the lower reaches of the Mara River where it crosses the Kenya/Tanzania international boundary, to 1950m on top of the Siria Escarpment and Ngama Hills tothe west and east respectively. The Reserve forms the northern portion of the Serengeti/ Mara ecosystem (Dublin, 1991). It is bounded on the north-east by the Loita Plains, on the east by the Laleta Hills, on the west by the Siria Escarpment, and on the south by the northern Serengeti National Park. There is an annual mean gradient in rainfall across the Reserve from ca. 900 mm in the east around the Ngama Hills to ca. 1.500 mm in the west along the Siria Escarpment (Masai Mara Ecological Monitoring records). The poorly drained `black cotton' soil areas supports the vast undulating areas of Themeda triandra grasslands that are the major vegetation community of the Reserve. This is the dry season habitat for the annual migration of wildebeests, zebras and Thomson's gazelles from the adjoining Serengeti National Park. The grasslands are intersected by the Mara, Talek and Sand Rivers and their numerous tributaries. The riverine forests and thickets provide shelter and security for rhinos. But it is the higher ground and hills with their shallow, porous, sandy soils, their greater cover of Croton and Euclea thickets, with the possibly greater abundance of herbs, legumes, shrubs and other favoured food plants, that constitute the preferred habitat for the majority of rhinos.
Mukinya ( 1973) records that the total area of the Reserve occupied by rhinos in 1972 was 749 km?, thereby giving a density of 0.14 rhino per km?. At present the total area occupied by rhinos is only 399 km?, with a density of 0.10 rhino per km? However, taking into account the 60 km? overlap of distribution (figure 2B), the total area occupied by rhinos is 459 km? with a corresponding density of 0.09 rhino per km?.
At the present time, the Reserve holds a modest and healthy population of rhinos, as shown in Figure 3, despite their near elimination in the Masai Mara between the 1960s and 1980s. The adult male: female ratio of 1:1.2 compares favourably with Mukinya's (1973) figure of 1:0.9, though the present cow: calf ratio of 1:0.6 is slightly less than Mukinya's (1973) figure of 1:0.8. However, indications are that between three to four calves might be born during 1996 which would improve this ratio.
Individual home range sizes were assessed by computing the area of a polygon by connecting the recorded peripheral points of each home range. Distribution areas were determined from groups of rhinos whose home ranges overlapped to a considerable extent. The measured home ranges, distribution areas, and population statistics were then compared with the findings of Mukinya (1973). Home range sizes for seven of the 11 adult males and five of the 13 adult females vary from seven to 126 km?, with a mean of 46 km?. Female home ranges are slightly larger than males. Females range from 12 to 126 km?, with a mean of 51 km?, while males range from seven to 83 km? with a mean of 42 km?. No account has been taken of eight adult rhinos whose home ranges extend into the northern Serengeti though the extent of their ranges within the Reserve are known. In 1971/72 when Mukinya (1973) did his studies, the Reserve rhino densities were higher and overall home ranges were smaller, varying from 5.6 km? to 22.7 km? with a mean of 13.l km?. The marked increase in the size of home ranges can be possibly attributed to each or a combination of the following: - Reduced competition for suitable habitat - Reduction in food resources due to annual, uncontrolled fires - Deterioration of the environment caused by excessive, off-road driving by thousands of tourist vehicles each year - Increased searching for mates by rhinos due to their lower densities.
Masai Mara, Kenya. The calving interval, to the nearest month, is known in 11 cases and varies from 16-34 months, with a mean of 25.4 months.
Masai Mara, Kenya. The only record of the age at maturity of a black rhino in the Reserve is that of Chebrech, who is recorded to have been born in May 1984 and who produced her first calf in December 1991. Based on a mean gestation period of 454 days (Hitchins & Anderson, 1983), Chebrech probably conceived in September 1989, at 64 months (5.4 years) of age.
