- Abiotic Factors - Biological Factors

Human-induced limiting factors

1. Veterinary control measures: Veterinary fences are probably the single most important determinant of buffalo distribution and numbers within Namibia and across the entire subregion.

   Figure 14: Present and potential buffalo range in the Caprivi Figure 10: The location of veterinary fences Figure 6: Mean annual rainfall in Southern Africa Figure 7: Potential buffalo densities in Southern Africa based on rainfall

   Large parts of the potential range (Figure 14) are not available to buffalo and within the allowed range many populations are becoming totally isolated as a result of the placement of fences (Figure 10).
2. Land Use Planning: Within the Caprivi and northern Botswana, the de facto location of human communities and their cattle not only dictates the application of veterinary measures but also results in direct competition with buffalo for land and grazing resources.
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3. Fragmentation: The subpopulation in the west of the Caprivi (Mahango and the western "Core Area") is effectively isolated from other buffalo in the Caprivi by lack of water in the central part of the Caprivi Game Reserve and it is also effectively isolated from Botswana by the veterinary fence (Figure 10). In the extreme western Caprivi a large part of the potential range is denied to buffalo by the settlement on both banks of the Kavango River north of the main road. If settlement and subsistence agriculture continue to develop in the vicinity of the Kwando River in Namibia, the buffalo populations in Mamili, Mudumu and the western "Core Area" of Caprivi Game Reserve (Figure 14) will become isolated subpopulations linked only through Botswana. In the area east of the Kwando River 'ribbon' subsistence cropping restricts buffalo access to water and creates a barrier to the Forest Reserve to the east. Settlement between Mudumu National Park and the conservancies to the north and along the southern boundary of the Forest Reserve is creating a barrier which will separate 'southern' buffalo from 'northern' buffalo. Settlement along the northern boundary of Mamili National Park will soon isolate this buffalo population completely.If the Salambala Conservancy is ever to maintain a sustainable buffalo population, it will come about through colonisation from Botswana across the Chobe River rather than through any eastwards migration of buffalo from Mamili or Mudumu. However, the potential buffalo range (Figure 14) along the Chobe River is severely threatened by an almost continuous belt of settlement.
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4. Fires have always been an important and natural process, and it is often argued that they have important benefits to plant communities.In recent years, however, the number of fires set has increased as human populations have grown, so areas get burnt much more frequently.

   Mendelsohn and Roberts (1997, pages 24-25) present a compelling picture of the gravity of the fire situation in Caprivi with burns commencing as early as April each year and continuing until December when over 60% of the vegetation has been burnt and the total count of individual fires may have exceeded 3,000. Fire management is needed to control this situation. It seems that at one time there was an extensive network of firebreaks in the Caprivi to control fires and it would obviously be beneficial if these could be resuscitated.
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5. Illegal Hunting: Although there is undoubtedly a high level of illegal offtake in the project area (in parts of Angola this hunting may be totally unsustainable), this may be less important than the previous factors. The illegal hunting is carried out in situations where the higher-valued uses of buffalo cannot be realised due to lack of empowerment over natural resources, the failure to develop management institutions and a lack of incentives for conservation.

Abiotic limiting factors

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Buffalo are regulated by their food supply - more particularly, it is the decline in quality and quantity of available food below the minimum maintenance level required by buffalo during the dry season that limits the population (Sinclair 1975).

1. Rainfall (Figure 6) is the primary driving vector which affects
   • surface water: notwithstanding any food production as a result of good rainfall, habitats may be rendered unavailable to buffalo if there is insufficient surface water. The development of game water supplies in the large Kalahari Sands area of the Western Caprivi Game Reserve would not only address this problem but would also allow the persistence of buffalo populations in areas away from the main rivers on a perennial basis. The difficulties of doing this are not underestimated: Mendelsohn and Roberts (1997, p. 39) show the average depth of water below the surface in western Caprivi as varying from as much as 300 metres in the west of the Caprivi Strip to 35 metres in the east. A number of boreholes have been sunk in the area but most are non-functional and would not provide the water needed for large buffalo herds.
   • the overall carrying capacity of land (Figure 7) for buffalo through food production;
   • Nutrition effects the fecundity of female buffalo;
   • the maximum growth rate of buffalo populations;
2. Soil fertility influences overall food production to a secondary extent.
3. Temperature is a determinant of buffalo behaviour in that they are obliged to seek shade whenever temperatures exceed a certain threshold.