Frequency of movements of small mammals among Atlantic Coastal Forest fragments in Brazil

Rates of interfragment movements were estimated for small mammals inhabiting a group of eight Atlantic Coastal Forest fragments, surrounded by grassland matrix, in order to understand the degree to which each species' population was isolated. Didelphis aurita showed the greatest movement rate (19.4% of recaptures showing interfragment movements), followed by Metachirus nudicaudatus (10.0%), Philander frenata (7.5%), Nectomys squamipes (3.6%), Micoureus demerarae (1.2%) and Akodon cursor (0.25%). Interfragment movements were not detected for Caluromys philander, Oecomys concolor and Oligoryzomys nigripes. Species can be placed along a continuum which goes from species that are represented by a single population in the whole study area, through those with metapopulations, to species that have isolated populations in each fragment. Ability to move among fragments was not related to abundance in the matrix; nevertheless, such ability helps to explain the persistence of species in fragments otherwise too small to support viable populations.