An investigation of urban bat ecology in Baltimore, Maryland

Abstract

In North America, bats are a taxon of concern that play an important role in insect control, and their response to urbanization varies. I wanted to discover if evaluating environmental and socioeconomic variables present in an urban landscape can help determine what bat species were present and how active these species were. Research occurred in Baltimore, Maryland, a 'shrinking' city in the eastern US, which had no prior research on the bat community. For my first project, I used active acoustic monitoring to evaluate how bat activity levels (amount of detected acoustic sequences) and the bat community varied along both a direct and indirect rural to urban gradient. Nine sites along the Gwynns Falls watershed in Baltimore County and City were used the gradient. Over 1,500 sequences (detection files) were recorded from six species and I found that the direct and indirect measures of urbanization gradient used are not a predictor of bat presence and activity. For my next project I used passive acoustic monitoring to record bat activity at 32 vacant lots within Baltimore City to determine which environmental and socioeconomic variables best predict bat species richness and activity at these small, informal, understudied urban greenspaces. Environmental and socioeconomic data was obtained using on-site measures, GIS, and US Census data. There were no predictors for overall species richness. Canopy-associated measures at both the site and neighborhood scale, streetlights, site distance from water and the urban core, residential race and income, old housing, and rental housing were all common predictors of bat species' activity levels. Species relationships with these predictors varied and some species had additional predictors, suggesting that bats use the urban landscape to different degrees. Some larger lots could potentially be managed to have vegetation structural complexity (allowing both canopy cover and open space to accommodate bat species with different traits), but many lots are too small to do this. Vacant lots closer to water and larger patches of forests have the most potential to be managed for bats.