Patch or mosaic: bat activity responds to fine-scale urban heterogeneity in a medium-sized city in the United States

Many recent studies have suggested that cities are spatially heterogeneous. Only limited research has investigated whether urban heterogeneity influences the distribution of bats in a city. Between 2010 and 2012, we acoustically surveyed bats in Waco, Texas, a medium-sized city in the United States. Seven species were detected, five in adequate quantity for analyses. Three distinct distribution patterns were evident (Mexican free-tailed bats; red bats and evening bats; big brown bats and cave myotis), reflecting the distinct functional guilds of these species. Bayesian conditional autoregressive models indicated that tree-dwelling red bats and evening bats were influenced by variables describing heterogeneity of urban vegetation. Big brown bats and cave myotis were associated with variables related to water sources. Mexican free-tailed bat distribution could be explained well by variables related to urban buildings and other constructions. Our modeling also suggested that urban socioeconomic heterogeneity influenced bat distributions. Distributions of tree-dwelling bats corresponded to income level. Distributions of Mexican free-tailed bats, big brown bats, and cave myotis related to human density. These results support the idea that a city comprises a mosaic of habitats as perceived by various species of bats and likely by other species of wildlife in urban settings.