The effects of the creation of a hydroelectric dam on small mammals' communities in central Brazil

Hydroelectrics are proposed as a solution to the increasing energy demand in developing countries. However, dams interrupt river flow; emit greenhouse gases, and cause habitat loss and fragmentation. Here, we evaluated changes in the diversity of small mammals during the construction of the Luís Eduardo Magalhães hydroelectric dam in central Brazil. Two sites, both located above the maximum filling of the dam, were sampled before (2001) and after (2002) the flooding. We used wire mesh traps and sherman traps for the total capture effort of 5,940 trap-nights. We captured 88 individuals from 13 species - 5 marsupials and 7 rodents. We expected an increase in the abundance of small mammals immediately after the flooding due to the fleeing of individuals from the flooded areas, with a following increase in density dependent mortality. However, our results indicated lower values of abundance and/or richness of small mammals after the flooding. In addition, live traps were frequently found overturned and with signs of attacks from potential predators of small mammals. Results suggested that predation pressure probably increased after the flooding, thereby causing a reduction in the abundance and/or richness of small mammals.