THESIS FOR DEGREE OF DOCTOR OF PHILOSOPHYThe ecology of rodent pest species is an important aspect that enables understanding of population characteristics and the type of crop damage caused by rodents in different locations. It is a basis for effective Ecologically-Based Rodent Management (EBRM) strategies. Rodent pest species are found in different parts of the world and have adapted to different life-styles such as terrestrial, aquatic, arboreal and underground dwellings. Rodent pests are seed/seedlings predators and cause high crop yield losses in the field and the storage. They also transmit many diseases to humans and animals. Studies carried out in areas with bimodal rainfall patterns in Tanzania and elsewhere have reported that rodent pests are generalists as well as omnivorous. Their breeding patterns depend on food availability and/or rainfall. The current research aimed at understanding the ecology and population characteristics of the dominant rodent pest species in semi-arid areas of Tanzania as a basis for effective EBRM.funded by the Bill and Melinda Gates foundation.