Determinants of microbat communities in urban forest remnants: a rapid landscape scale assessment

Urbanisation affects fauna in many ways; with some species persisting and going on to dominate urban habitats, while other species decline over time due to habitat disturbance and modification. Microbats comprise a major component of remnant mammalian fauna in urban areas but we have a comparatively poor understanding of how they respond to urbanisation compared to other taxonomic groups. We investigated the impacts of an urban gradient on microbat communities of habitat remnants on the Gold Coast, south-east Queensland, Australia. We conducted acoustic surveys of 34 sites categorised as urban, peri-urban or rural, with an additional five reference sites. A combination of landscape and habitat elements were quantified for each site and their influence on the richness and calling activity of microbats determined. Overall, more microbat species were detected in reference sites followed by peri-urban sites. Rural and urban sites had similar richness, but only 50 % overlap in species recorded. After accounting for sampling effort peri-urban sites were found to have the greatest species richness and calling activity. Three species accounted for 45.4 % of the variation in microbat species detected. Using generalised linear mixed models we found that site area and the extent of urban development in the landscape (i.e. urbanisation index) had the greatest impact on microbat richness and calling activity. Models including logging (clearfelling) and hollow-bearing tree measures were also important. Our results support the use of the urbanisation gradient as a key measure to quantify the impacts of urbanisation on biodiversity. Logging history plays an important role across the landscape as it is a potential driver of other landscape variables such as tree species diversity, stand density and hollow-bearing tree density.