Population dynamics of small rodents in a grassland between fragments of Atlantic Forest in southeastern Brazil

Population dynamics and reproduction of four species of muroid rodents (Akodon cursor Bolomys lasiurus, Oligoryzomys nigripes, and Mus musculus) were studied through capture-mark-recapture in a grassland between fragments of Atlantic Forest from March 1998 to February 1999. A. cursor and B. lasiurus accounted together for 93.5% of all captures. O. nigripes and A musculus reached highest population sizes by the end of the dry season. A. cursor was most abundant during late dry/early wet season, however, its population sizes were higher in the wet season than in the dry season. Populations of B. lasiurus were highest during the dry season, although their population Levels varied less than those of A. cursor. The differences in the pattern of population fluctuations of the two latter species can be explained by differences in their feeding habits, as B. lasiurus feeds mostly on grass seeds (most abundant during the dry season), whereas the diet of A. cursor includes a high proportion of insects, which are most abundant during the wet season.