Population dynamics and breeding patterns of Mastomys natalensis Smith 1932 in irrigated rice in eastern Tanzania

The population dynamics and breeding patterns of the Multimammate rat, Mastomys natalensis, were investigated in irrigated rice cropping systems in eastern Tanzania in 2010/ 2011. Population abundance varied with habitat and crop growth stages. In both rice fields and fallow land, the highest population peak was observed during the dry season from July to October. The results show that M. natalensis is sexually active throughout rice cropping season in the study area, although it reaches the highest level at maturity stage of crop growth. Breeding occurred in the dry and wet seasons, and suggests that it was highly influenced by the presence of a rice crop in both seasons. More juvenile individuals were recorded at transplanting stage in each season and few in the subsequent crop growth stages in all habitats. Breeding, therefore, was not seasonal and seemed not to be associated with rainfall patterns. The sex ratio of M. natalensis was not skewed to either males or females.