Urban Bats: Distribution, Roost Selection, and Foraging Site Selection

The global trend of urbanization has led researchers to examine the influence of human dominated landscapes on wildlife populations. While many species have not been able to thrive in cities, some species have shown the ability to adapt to the urban environment. This dissertation study focused on how bats adapted to a medium-sized city in the United States, with emphases on their general distributional patterns, roost selection, and foraging site preference. In the first project, I conducted acoustic driving surveys to map the distribution of bats in and around the city of Waco, Texas. Bayesian spatial modeling showed that distributional patterns of different bat species were affected by each bat species' functional guild. Modeling also showed that socioeconomic heterogeneities with in the city influenced bat distributional patterns. This project suggested that the urban environment was not a homogenous patch and bats responded to fine scale urban heterogeneities. In the second project, I concentrated on the roost selection of Mexican free-tailed bats (Tadarida brasiliensis), the most common species in this study. Based on 54 day-roosts identified in buildings, I found that this bat species tended to choose tall buildings that were abandoned or empty. The presence of bird nests was also an indicator of the presence of a bat roost. In contrast to literature, factors affecting the thermal condition of a roost were not significantly influential in roost selection. I suggest that alternative roosts should be provided when bat-preferred buildings are involved in urban developments. In the third project, I investigated how urban night illumination affected insect prey availability and bat foraging activity. Findings showed that insects were usually more abundant at sites with stronger illumination, thus attracted more foraging activities. However, during the winter bats still foraged more often at sites with stronger illumination, although insect availability was not necessarily better at those preferred sites. Overall, it is evident that a medium-sized city like Waco provides sufficient resources to support several bat species. However, more research is needed to fully understand urban bat ecology to achieve the greater goal of harmonious coexistence of humans and wildlife in urban settings.