Abstract:We sampled the seasonal diversity of rodents and shrews in two neighboring game reserves in the savannah biome and assessed the influence of competition and abiotic processes on species composition patterns at habitat and reserve scales. We used null models and multivariate analyses to test whether the observed patterns differed significantly from those expected by chance. Species richness estimators indicated that rodent and shrew inventories were relatively complete. Rarefaction curves showed that small mammal species richness was higher at the Mkhuze Game Reserve than the Kube Yini Game Reserve, though it was highest in the Acacia woodlands. Rodent diversity was highest during winter. Rodent and shrew species composition was significantly correlated with grass height, tree density, and ground cover. Furthermore, rodent and shrew assemblages were nested at the reserve scale. Only nestedness at the broadest scale (both reserves, both seasons combined) was significantly correlated with landscape and microhabitat variables. Conversely, there was little evidence that competition influenced rodent and shrew species composition. Results showed that species composition patterns of small mammals in the savannah biome are related to abiotic processes operating at local and regional scales, suggesting that microhabitat characteristics and regional processes like immigration and extinction drive assemblage structure.