- conflict with humans -

Various aspects of hippo behaviour have already been mentioned in this report including the concept of a 'living space', feeding behaviour, hippo movements and factors leading to homeostatic population regulation . In this section it is perhaps only necessary to reiterate those behavioural characteristics of hippo which affect management.

Hippo have the dual requirement of a daily living space and a grazing range (Olivier & Laurie 1974). This affects the manner in which they use resources and survive in areas which are heavily populated by humans and where they are hunted. Their feeding behaviour is nocturnal and they are able to hide in narrow channels and impenetrable reedbeds during the day where they are relatively safe from human predation. They can remain under water for periods longer than five minutes and surface to breathe with only their nostrils appearing above the water.

It is generally considered that the hippo's nocturnal feeding behaviour arises from a need to avoid direct sunlight on their sensitive skins (HSG 1993). However, in areas where hippo are totally secure they frequently graze during the day and bask exposed to the full heat of the sun (e.g. Mana Pools on the lower Zambesi river in Zimbabwe). This would suggest that their nocturnal habits may be a survival trait arising largely from the avoidance of humans.

Hippo are capable of moving long distances in search of food and, in the extreme, to occupy new ranges. In the Caprivi, hippo move up to 90km from the Kwando river into the omurambas of the Western Caprivi during good rains (Mayes pers.comm.). The example of Huberta illustrates the ability of hippos to cover great distances without being detected and with considerable stealth. The colonisation of artificial pans and dams in Hwange National Park, Zimbabwe, entailed hippo moving more than 100km from the Zambesi River which they achieved without being noticed en route. This has relevance to conservancy development in Namibia: by creating conditions which are favourable for hippo (e.g. Joseph Mbambangandu conservancy), it is likely that sooner or later they will move in to occupy the vacant niche.

Hippo group size is an extremely variable parameter. Stander (2004) found that the average group size in the Caprivi was 5 but groups as large as 45 animals were observed. Group size is most likely to be small where hippo are limited in resources or under pressure from human predation. Single adult males are a feature of hippo populations and arise from unsuccessful competition to secure females. Lone bulls frequently carry the scars and wounds of intra-specific fighting and may be dangerous to humans. It would seem logical to target such individuals in any programme of hippo exploitation.

Hippo males spread their dung by vigorous 'paddling' with their tails both on land and in water. This behaviour is thought to be a signalling function rather than a territorial display (HSG 1994). The nature of this signalling may, in many cases, be a prelude to aggression either to humans or to other hippos and is often indicative of some degree of uncertainty on the part of the animal and, hence, potentially dangerous situations (Parker pers.comm.).

Although hippo are predominantly grazers of wild grasses and sedges, given the opportunity they will consume maize, sugar cane, pumpkins, beans, cabbages, melons and other vegetables. Their depredations on crops planted close to river margins can be devastating and, perhaps unwittingly, they discourage illegal stream bank cultivation.

Conflict with humans

Hippo damage crops and are a physical threat to humans. The data relating to hippo incidents in the Caprivi Conservancies are shown in Table 5 and Figure 7 (NNF 2004, Conservancy Event Book). The greatest conflict between humans and hippos occurs on the Kwando River frontage and it is clear from Figure 7 that the incidents reach a peak in the crop growing season. In 2003 the number of incidents involving hippo in the

eastern Caprivi conservancies was 263 - which exceeds the number of incidents involving elephant (253). O'Connell-Rodwell (et al 2000) estimated the value of damage to

crops by elephants from 1995- 2000 for the whole Kwando River region at about N$20,000 per year: it might be expected that

the value of hippo damage is similar. This has significant effects on household livelihoods.

It cannot be inferred from the data of Table 5 that the overall number of hippo incidents is increasing (as is the case with elephant). In the Kwando conservancies (including Wuparo) the number of incidents decreased from 2003 to 2004. Interestingly Wuparo conservancy suffers a significant number of hippo incidents. As Stander (2004) does not record any hippo in Wuparo it must be assumed that the animals originate from Mamili. In the extreme east of the Caprivi, despite far lower numbers of hippos, the numbers of incidents in Kasika and Impalila increased in 2004.