The multimammate mouse,Mastomys natalensis (Smith,1834) ,is an important agricultural pest in sub Saharan Africa where it can cause severe crop losses.The eruptive nature of this rodent species raises serious concerns to farmers in the region.The population dynamics of this species seems to be influenced by local conditions within a locality.The aim of this study was to investigate population dynamics and the breeding pattern of M.natalensis in three locations with different rainfall patterns and agricultural practices.Population densities were higher in rice irrigated systems compared to maize fields and fallow land.M.natalensis showed extended breeding in irrigated rice and in maize fields in the wetter areas.The breeding period was shorter in areas that were relatively much drier.The study suggests that food availability is the major factor contributing to the observed trend in population dynamics in the different locations.