Gakahu, C.G., 1991. African rhinoceroses: challenges continue in the 1990s. Pachyderm 14: 42-45, figs. 1-4, table 1
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| Location: |
Africa |
| Subject: |
Distribution - Status |
| Species: |
African Rhino Species |
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Numbers, distribution and the trend of population, are vital data for conservation of rhinos. In 1981 Hillman provided the first scientifically-based continental estimates for African rhinos. These figures were updated by Western and Vigne in 1984, who estimated 800-900 black, 3,920 southern white and 20 northern white rhinos. Another survey conducted in 1987 estimated 3,800 black rhinos, 4567-4635 southern white and 22 northern white. The survey reported here looks at the fate and performance of African rhinos in the last six years. The survey was conducted by the African Elephant and Rhino Specialist Group (AERSG) of IUCN with funding from Wildlife Conservation International.
Surveys Methods
Questionnaires were sent out to 30 individuals in rhino range states. The questionnaire requested information on numbers, distribution range, density, recent population trends, and aspects of rhino horn trade. Other information concerned overall management needs and problems. Population estimates data were ranked using the following categories:- A. aerial or ground census; B. non-scientific reconnaissance survey; C. informed guess.
Levels of reliability of data as percentages of all the returned questionnaires for the three species are as follows:-
Species A B C
Black 55 20 35
Southern White 68 16 16
Northern White 100 - -
Category A estimates for black rhinos were all from southern Africa and Kenya in eastern Africa. The northern white rhino is extinct except for the single Garamba population in Zaire, hence the 100% score in category A.
Rhino Numbers
The national estimates and trends of black and white rhinos in Africa since 1980 are summarized in the Table. Black rhino numbers have dropped from 8,800 in 1984 to 3,390 in 1990, a 61% decline in 6 years or 20% per year. In some countries like Sudan, Uganda, Mozambique and Somalia the species has become extinct. These local extinctions had been predicted in surveys conducted within the last ten years.
Another significant feature is the change in the location of the large populations. In 1984 Tanzania had the largest number of animals and accounted for 35.5% of the continental total; this has dropped to only 5.5%. Similarly Zambia's 18% in 1984 has become 1.2% today. A contrary change has occurred in southern Africa. South Africa and Zimbabwe accounted for 19% and 7.3% in 1984 while today their respective figures are 50.1% and 18.5%. This positive shift is not due to increased numbers but becaise of decline in most of the other African countries.
Regionally, in 1984, southern Africa represented 52%, eastern Africa 44% and west-central 3% of the continental total. These proportions have shifted to 82%, 17% and 1% respectively. Finally, it is worth noting that 90% of all remaining black rhinos are to be found in Zimbabwe, S. Africa, Namibia and Kenya. Alongside the drastic decline in numbers the species range has contracted considerably. This has isolated small populations in the once expansive and ecologically diverse black rhino range in Africa. However , it is worth noting that the overall continental rate of decline has dropped in the last three years as shown by the flexing of the curve in Fig.2.
The increase in southern white rhino reported by Western and Vigne in 1984 has been maintained in South Africa, Namibia and Kenya. The species population in Zimbabwe remained stable but declines were recorded in Swaziland and Botswana. South Africa, Zimbabwe and Namibia have 97% of the continental total. The introduced Kenyan population in sanctuaries has grown at the rate of 16% per annum from 25 to 65 individuals over the last 10 years. Southern white rhino total population in Africa now stands at 4,745 compared to 3,841 in 1980, an increase of 2.35% per annum. The northern white rhino has decreased by over 97% in the last decade although the Garamba population, which had dropped to 20 individuals by 1984, now stands at 26.
Trends in Population Sizes
The size distribution of existing black rhino population displays a larger proportion of even smaller populations than the 1984 survey. No population has more than 400 individuals. In 1980 75% of the continental populations had less tham 100 individuals: this has gone up to 80% today. Fig 3. shovel percentage cumulative frequencies of populations of various sizes in 1980 and in 1990. The two curves are significandy different (Kolmogorov-Smirnov 2-sample test: D=O. P =0.001, N=24), with the shift left due to an increase i proportion of small size populations. The percentage quencies of the number of black rhinos within various p lation sizes in 1980 and 1990 is shown in Fig 4. The difference between the two curves is also significant when subjected to the same test (D=0.666, P=0.001, N=24). Fig 4 shows the 15% of all rhinos living in populations of 100 individuals or less in 1980 has increased to 30% today. Similar figures for populations of 400 individuals are 32% and 80% respectively. A significant factor that has contributed to the shift of both ogives is the extinction of some populations which had under 10 individuals in 1980. Generally the survey reveals that the alarming decline of rhinos continues over most of the species range although at a lower rate. The exceptions are southern Africa and Kenya where rhino popula- tions are stable or increasing, which is a reflection of the commitment and efficiency of wildlife authorities and, especially, the development and implementation of rhino management plans.
In countries which have experienced major civil unrest in the last decade rhino numbers are negligible; to all intents and purposes the rhino is extinct. The ready availability of automatic weapons, allocation of nearly all resources to war and the fact that poaching becomes a means of survival for people in remote areas during civil disturbance, are the main reasons for the demise of rhinos in these countries.
The cause of continuing pressure on rhinos is the intolerable trade in their horn which is used mainly for making traditional medicines in the Far East. The limited supply has caused prices to rise to a level which encourages poachers to take great risks. What needs to be done has been repeated time and again: reinforce anti-poaching measures; improve regional co- operation of management and law enforcement authorities; find acceptable substitutes for rhino horn as medicine; enforce CITES regulations.
Half of all the world's black rhinos are in Zimbabwe and three other countries have more than 80% of the rest. South Africa holds nine of every ten white rhinos. Even to a layman the `all eggs in one basket' risk is obvious. For the conservationist questions of genetic depression, biased sex ratios and age structures and active management are the obvious challenges. Conservationists most often operate in areas of peace but the risk of future civil unrest in the countries with nearly all rhinos cannot be ruled out. Personally, I see a future challenge: endeavour to influence sociopolitical and economic systems so as to prevent those civil wars whose impact on rhinos and other wildlife is only too evident.
Nearly all rhinos are in parks or on private lands. Those outside protected areas and some in the larger parks are either scattered individuals or live in very small populations. Such conditions expose the animals to biological and environmental problems that accelerate their extinction and, because of limited resources, their protection is beyond the capability of wildlife authorities. Sanctuaries are often the rhinos' only chance of survival but require much forethought and careful planning.
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African rhinoceroses: challenges continue in the 1990s
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