Effects of urban habitat fragmentation on common small mammals: species versus communities

There is an increasing interest in understanding how species respond to the modifications of habitat attributes in urban areas. Patterns in the occurrence and abundance of small mammal communities in 15 isolated patches of remnant natural and semi-natural habitat of Porto Metropolitan Area (Portugal) were assessed against environmental characteristics (from both the patch and the surrounding matrix) of each patch using multiple regressions and canonical correspondence analysis. Four species of common small mammals were found: wood mouse (Apodemus sylvaticus), greater white-toothed shrew (Crocidura russula), Algerian mouse (Mus spretus) and house mouse (Mus musculus). Our results showed that both relative abundance and species richness were negatively affected by urbanization. The species richness also displayed a negative association with the increase of forest around the patch but relative abundance showed the opposite trend. At the species level, the relative abundance of A. sylvaticus and C. russula showed a negative association with urbanization. Our results reveal that these two species also benefit from a mosaic of habitats and pervious areas in the surrounding matrix. The relative abundance of M. spretus and M. musculus showed a negative effect of forest area around the patch. Understanding how the increase of urbanization affects small mammals will be particularly useful for the managers of urban landscapes, as these animals occupy a pivotal position in the ecosystems.