Forest structure and vertical stratification of small mammals in a secondary Atlantic forest, southeastern Brazil

This study investigated the differential capture rates of small mammals in different strata of a secondary forest, Minas Gerais State, Brazil. From March through October 1994 mammals were live-trapped at ground, understory and mid-story level. Five species of marsupials and six species of rodents were recorded. Didelphis aurita, Marmosops incanus, Metachirus nudicaudatus, and Oryzomys spp. were captured mostly on the ground, while Caluromys philander, Micoureus demerarae, Rhipidomys mastacalis and Sciurus aestuans were sampled mainly at 5-12 m, height. Species richness was correlated with structural complexity of the forests surveyed. On the other hand, a relationship between species richness and habitat heterogeneity was not detected. These results suggest that local saturation of small mammal species, rather than regional species richness, is determined by the level of habitat complexity. The conservation of stratified forests, such as those found at the Parque Estadual do Rio Doce and the other sites in the Rio Doce valley, are therefore essential for the maintenance of local species diversity.