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3.3 Wildlife and forestry/agriculture
Wild animals exert significant influences on food production systems which may be positive or negative. Positive influences include the role of wild animals as seed dispersal and pollination agents as well as use of wild animal droppings as fertilisers. Many species of birds and mammals such as bats, monkeys, baboons and squirrels are known to spread fruit trees by their feeding action. A study in the Cote d'Ivoire found that sites where elephants had vanished long ago lacked saplings of certain tree species which are known to be dispersed by elephants (Alexandra, 1978)
On the negative side, some wild animals species are known as reservoir or intermediate hosts for parasites and disease pathogens which can be transmitted to man and his domestic stocks. Other wild animal species including both vertebrate and invertebrate species cause destruction to food and cash crops both during crop development and post-harvest storage. Vertebrate damage involves a wide range of wild animal species and a variety of crops (Table 3.13). The activities of the pest may result in direct crop losses, i.e. actual destruction of the food by the feeding of the pest and contamination or indirect losses which may occur through damage to production systems and equipment. Major vertebrate pests causing crop damage in Africa include a wide range of rodents and birds (see e.g., Ward? 1979; Elliot, 1979; Taylor, 1984; Ntiamoa-Baidu, 1988; 1989 (a); (b); Elias, 1988).
Birds, sometimes numbering in millions, can cause serious damage to grain fields. Species of birds causing damage to agricultural crops in Africa include weaver birds (Ploceidae), waterfowl (Anatidae), Parrots (Psittacidae) and seed eaters (Fringillidae), and crops frequently attacked include rice, maize, sorghum and oil palm. The main losses result from feeding of the birds on maturing crops, but losses at storage sites can also occur through feeding activity of the birds and contamination by roosting birds. The red-billed quelea Quelea quelea is the most important granivorous bird pest in Africa. The range of the species extends over 20% of the land area of the continent and affects the food production capacity of some 25 countries.
Estimates of annual losses of cereals to the red-billed quelea range from at least $1 million in Somalia to $ 6.3 million in the Sudan (Elias, 1988). Other weaver birds which often cause seasonally localised but serious damage to grains include the red-headed quelea, Quelea erythrops, the red bishop Euplectes orix and the yellow crowned bishop E afra Ntiamoa-Baidu (1989) reports destruction of whole rice fields, mainly by these three species in northern Ghana. Once the birds arrive in a good feeding area, their numbers can build up very quickly to several thousands and whole fields can be rapidly destroyed within a very short time. The population of birds at one roost monitored in the northern Ghana study increased from a total of 85,000 at the end of April when the birds started arriving in the area to over 400,000 within one month.
Table 3.13 The major
vertebrate pests of Africa.
(Adapted from Taylor; 1984 Ntiamoa-Baidu, 1988)
|Widespread pests of cereals|
|Red-billed quelea Quelea quelea||Small-grained cereals||Savannah||W, E, S|
|Multimmate rat Mastomys natalensis||All cereals, cotton, ground nuts,||Savannah, Forest||W. E, S|
|Nile rat Arvicanthis niloticus cane, cotton||Most cereals, sugar||Savannah||W. E, Nile Valley to Egypt|
|Local agricultural pests|
|Village weaver Ploceus cucullatus||Cereals||Forest, Savannah||W, S|
|Spanish sparrow Passer hispaniolensis||Cereals||Cultivated areas||N|
|Red-headed quelea Quelea erythrops||Cereals||Wetlands' savannah grasslands||W|
|Jirds Meriones spp.||Cereals, ground nuts||Sandy areas||N|
|Giant Rat Cricetomys sp||Cocoa, oil palm||Forest||W|
|Squirrels Oenomys, Stochomys, Funisciurus spp||Cocoa, oil palm||Forest||W|
|Gerbils Gerbillus, Tatera, Taterillus spp.||Cereals, ground nuts||Semi-desert, savannah||W, N, E, S.|
|Zebra mouse Rhabdomys pumilio||Cereals, conifers||Highlands||E, S|
|Grasscutter (Cane rat) Thryonomys swinderianus||Rice, maize, sugar cane, cassava||Forest||W, E, S|
|Urban and peridomestic pest|
|House sparrow Passer domesticus||Cereals||Built-up and agricultural areas||N, W, E, S|
|Black rat (Roof rat) Rattus rattus growing crops||Post-harvest and irrigated fields||Ports, towns, farms||N, W, E, S|
|Brown rat (Norway rat) Rattus norvegicus||Post-harvest and manufactured produce||Ports, towns||N, W, E, S|
Crops destroyed by rodents include rice, maize, sorghum, millet, wheat, cocoa, oil palms and coconut. Sugar cane is particularly susceptible to rodent damage. The gnawing of the rodents opens the rind and the subsequent fermentation reduces the sugar content so dramatically that often the entire stalk is rendered useless. Rodent damage is not limited to field crops as considerable damage is also caused to stored products.
A wide range of other mammalian animal species including bats, baboons, monkeys and elephants can also cause significant damage locally to food crops such as plantains, bananas, cocoyam as well as cocoa and oil palm plantations. Bell (1984) reports that in the Lilongwe area of Malawi, crop damage was mainly caused by elephants, bush-pigs, baboons, vervet monkey Cercopithecus aethiops, eland Taurotragus oryx and Kudu Tragelaphus strepsiceros, with elephants and bush-pigs accounting for 80% of the total damage. In Zambia, the main wild animal pests were bush-pigs, monkeys, baboons, elephants, hippopotamus and porcupine Hystrix cristata (Table 3.14)
Table 3.14 Wild animals as pests in the Upper Lupande Game Management Area, Zambia. (Source. Balakrishnan & Ndhlovu, 1992)
Frequency of damage mentioned (n=135)
|Bushpig Potamochoerus porcus Vervet monkey Cercopithecus pygerythrus||
|/Chamca baboon Papio ursinus||
|Elephant Loxodonta africana||
|maize, sorghum. fruits|
|Hippopotamus Hippopotamus amphibius||
|maize, rice, vegetables|
|Porcupine Hystrix cristata||
|Warthog Phacochoerus aethiopicus||
|Kudu Tragelaphus strepseceros||
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