Population ecology of Mastomys natalensis (Smith, 1834). Implications for rodent control in Africa. A report from the Tanzania-Belgium Joint Rodent Research Project (1986-1989)

Abstract

The population ecology of multimammate rats Mastomys natalensis (Smith, 1834) was studied in a fallow land population in Morogoro, Tanzania. Monthly data were collected by removal trapping and a capture-mark-release study between November 1985 and February 1989. Population size fluctuations, reproduction, growth and survival are strongly related to rainfall patterns. The main breeding season starts after onset of heavy rains in the second half of the wet season (April-May) and continues until September when adults disappear. In most years the young do not mature before the start of the next main breeding season. When however rain is abundant early in the wet season, there is already reproduction in January-February. The produced extra generation participates in the main breeding season and creates a potential for outbreak densities later in the year. Reproduction is possibly induced by environmental triggers, perhaps chemicals in sprouting vegetation. Mastomys prefers dense vegetation but has a wide habitat tolerance and an opportunistic diet. Daily movements are short but dispersal is very important. Recommendations for pest control of Mastomys are formulated. Preventive control actions or habitat sanitation are unlikely to be effective because of the opportunistic generalism and high dispersal rate of the rats. A model to forecast outbreaks, utilizing rainfall data, is proposed. The model is consistent with earlier outbreaks in Tanzania.