The Eastern Arc Mountains (EAM) contain some of the most biologically diverse and endemic-rich montane ecosystems in all of Africa. Because of the staggering degree of biodiversity, how little we know about the biota of the EAM and the rapid degradation of the remaining montane forests of these mountains, we are studying the natural history and biogeography of the small mammals (shrews and rodents) of this archipelago. We are also interested in specific questions such as the effects of forest fragmentation on and elevational distribution of EAM small mammals. To date we have surveyed the South Pare, East Usambara, West Usambara, Nguru, Uluguru and Udzungwa Mountains. We have documented a rodent fauna that is widespread across the archipelago, although restricted to montane and submontane habitats. Shrew species are much more patchy in distribution with each EAM or subset of mountains holding at least one seemingly endemic species, suggesting that speciation has contributed to the current pattern of species richness in insectivores. However, further analysis is required to discern how dispersal, extinctions and/or speciation have contributed to this pattern. Importantly, we have found very few introduced, exotic or savannah dwelling species in our surveys of undisturbed forests, even in forests in close proximity to disturbed areas or human habitation.