Spatial and temporal population dynamics of rodents in three geographically different regions in Africa: Implication for ecologically- based rodent management

As part of a three years study to develop ecologically-based rodent management (EBRM) in southern Africa, a Capture Mark Recapture study was carried out in Tanzania, Namibia and Swaziland to establish the demographic patterns and population dynamics of rodents. Two study -grids were established in each country. In Tanzania, ten species of rodents and one shrew (Crocidura sp.) were identified in the study area. The rodent species consisted of Mastomys natalensis, Aethomys chrysophilus, Arvicanthis neumanni, Gerbilliscus vicina, Acomys spinosissimus, Lemniscomys griselda, Lemniscomys zebra, Rattus rattus, Graphiurus sp. and Mus minutoides. Mastomys natalensis was dominant and contributed more than 70% of the captures. In Namibia, five species were captured, namely Mastomys natalensis, Gerbilliscus leucogaster, Saccostomus campestris, Mus minutoides and Steatomys pratensis. Mastomys natalensis contributed about 50% of the captures. In Swaziland, only M. natalensis was captured in the study grids. There was a clear pattern in the population dynamics, with breeding confined to the wet seasons in the three countries. Mastomys natalensis was the dominant pest species, for which EBRM should focus on. The highest population density of M. natalensis occurred during and after the rains, which coincided with the most susceptible phenological stage of crops. The breeding seasonality and density fluctuations observed in the three countries conform to observations made elsewhere in Africa, which support the hypothesis that rainfall events promote primary productivity on which murid rodents depend. Development of EBRM in these countries will be determined by the local conditions and how they influence the demographic processes of the rodent populations. EBRM should make use of the available ecological knowledge of the local rodent pest species and the focus should be on (ecological) management practices applicable at the community level including community based intensive trapping, field hygiene, removing cover and sources of food for rodents.