- North central Namibia -

Caprivi

The main hippo population in Namibia is in the Caprivi (Figure 13) and was estimated at 1,387 animals by Stander (2004) of which 872 were in State Protected Areas, 69 in conservancies and the remainder (446) in communal land.2 Martin (2005b) calculated that some 390 of these animals should probably be regarded as 'belonging' to neighbouring countries. It is difficult to infer any trends in the population because there are no survey data which compare readily with those of Stander (2004) and because the earlier data are too sporadic to permit any meaningful trend analysis.

Stander (2004) carried out the first survey in the Caprivi specifically designed to count the numbers of animals on the Caprivi floodplains, he estimated that there were some 1,400 hippo in the Caprivi (Table 1).

Table 1: Estimates for Hippo in Caprivi

The survey strata included the following areas :

Although the most extensive floodplains in the Caprivi occur along the Zambezi River, the hippo numbers are disappointingly low. This is entirely due to high density human settlement and cattle populations (Map 3). The high density hippo population in Mamili national park has been used to estimate the possible carrying capacity for hippo in the Caprivi - about 5,000 animals.

The hippo populations on the floodplains along international boundaries (Kwando, Linyanti, Chobe and Zambezi rivers) are shared with neighbouring countries (Botswana and Zambia). This has significant implications for any potential hippo harvesting programmes within Namibia.

The estimates for hippo numbers made in the course of other air surveys since 1980 are shown together with Stander's (2004) estimates in Analysis 5 and Figure 12. It is difficult to infer any trends in the population because there are no survey data which compare readily with those of Stander (2004) and because the earlier data are too sporadic to permit any meaningful analysis.

Stander's overall total for the Caprivi (1,387) and his estimate for Mamili National Park (560) are the highest yet obtained but both fall within the 95% confidence intervals of Craig's (1998) survey. Stander's estimate for Mudumu is lower than several earlier estimates and falls outside Craig's 1998 estimate. Stander's estimate for Mahango is lower than three previous estimates but falls within the confidence intervals of Craig (2000). Because of the mobility of hippo along watercourses it would be unwise to draw any conclusions about upward or downward trends in numbers.

It could be reasonably expected that some form of relationship exists between hippo population numbers and rainfall but, as stated above, the data are too scant to permit any meaningful exploration of this idea.

As might have been expected, the highest numbers of Hippo occur in State protected areas with more than 40% of the Caprivi total in Mamili National Park (Figure 13). An exception to this generality is on the Chobe River where slightly under 200 hippo were counted: in this case, the protected area is on the Botswana side of the border (Chobe National Park). Some 68 hippo counted along the Kwando River were allocated to the three conservancies (Mashi, Mayuni and Kwandu) and the number seen on the western side of the river within the Eastern Core of Babwata was significantly higher (91). However, these proportions are likely to vary as hippo move from one bank of the river to the other. The low numbers along the Zambezi and in Salambala conservancy (where there are extensive floodplains) is disappointing.

All hippo occur within the floodplains and riverine woodlands except in Mudumu where a small number occur on river banks fringed with mopane woodland (Figure 13). The most extensive floodplains occur along the Chobe/Linyanti and Zambezi river systems and these contain the fewest hippo: this can be attributed entirely to human population densities and cattle densities in the east of the Caprivi. The floodplains in Mamili support a relatively high density of hippo.

High cattle densities generally coincide with high human populations. Whilst it is generally clear that hippo avoid areas of intense human settlement, there are some exceptions to this rule (Figures 14). Some 60 hippo on the Okavango occur in an area of high human and cattle densities upstream of Mahango national park and a similar number occur in the Mayuni and Kwandu conservancies under the same conditions. Immediately upstream of Mamili on the Linyanti River is an area of dense human settlement with cattle which supports 50 hippo. Hippo exclusion due the effects of high human and cattle densities is most obvious in Salambala, Impalila and Kasika conservancies and along the entire the length of the Zambezi within Namibia. An area where more hippo might be expected is on the upper reaches of the Linyanti river where there are substantial floodplains coupled with low human and cattle densities.

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North Central Namibia

A small number of hippo occur on the Cunene River in the vicinity of the Ruacana Falls although it is not certain whether there are now any hippos downstream of the falls. Staff of the Cunene River Lodge estimate 25 hippo on the Cunene (Peter Erb pers.comm.). Recent information from reliable tour guides operating in the area (through Chris Roche pers.comm.) is fairly conclusive that there are no hippo west of the Ruacana Falls. Even if there were, the arid conditions of the area will always limit hippo numbers to a few individuals.There are also a few pockets of hippo on the Okavango River outside the Caprivi (less than 40 in total). Although the floodplains are not as extensive on this part of the Okavango River as, for example, below the Popa Falls, there are nevertheless numerous areas which would be suitable for hippo were it not for the fairly dense human settlement, crops and cattle along the river. The newly formed Joseph Mbambangandu conservancy near Shambyu on the Okavango River may well attract hippo to the floodplains in that area in the future ( Figure 11).The vegetation map of Joseph Mbambangandu conservancy has been done based on interpretation of aerial photography (Figure 11). It is possible that the effects of fires could have caused errors in the boundaries selected for the vegetation types.

The full extent of the Okavango River in Namibia appears in Figure 11 showing the few remaining localities with hippo and the floodplains which could provide suitable habitats for hippo. Mendelsohn & Obeid (2004) mention a few hippos remaining on the 'upper' Okavango. Current reports suggest that a few hippo occur in the area around Nkurenkuru and at the Cuito/Okavango confluence. Shortridge (1934) remarked on the paucity of floodplains associated with the Okavango River in Namibia above Andara.

There are few options for extending the range of hippo in the remainder of Namibia because of the absence of suitable permanent water supplies. The general feeling is that it would not be worthwhile stocking hippos in any of the large dams in the interior of the country because of the low carrying capacity of the pastures surrounding the dams. Reintroduction of hippo to the Orange River may be worthwhile and could assume the status of a flagship project. However, it should not be expected that the Orange could ever support large numbers of hippo as it falls below the 100mm rainfall isohyet.