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Research Area 2 - Bat communities and foraging ecology along an urban-rural gradient in Nanjing, China

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The relationships between urbanization, bat (Order: Chiroptera) community structure, and bat foraging ecology with insect prey will be investigated in Nanjing along an urban gradient. Many studies have examined the use of urban areas by bats and have found that bats prefer wooded or riparian areas within cities and avoid high density residential and commercial–industrial areas (Sparks et al. 2005, Hourigan et al. 2006, Walters et al. 2007). Fewer have examined the impact of urbanization on bat populations or community composition. These studies found that bat communities in urban areas had lower species richness than surrounding rural areas (Avila-Flores and Fenton 2005) or are dominated by a few common species that have adapted well to urban environments (Kurta and Teramino 1992, Sparks et al. 1998, Ulrey et al. 2005). A discouraging indicator is the negative effect of urbanization on insect abundance (McIntyre 2000, Kalcounis-Rueppell et al. 2007), the bat’s primary food source. No study has documented or tested how bat communities have responded to the fast transition from rural to urban in China.  

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The objective this study is to assess bat community composition, movement, and foraging ecology along an urban-rural gradient.  We will capture bats in the evening hours using two 12-m mist nets at 10 stream sites. Bats will be removed from the nets, identified using a taxonomic key, weighed, measured, sexed, and marked with a temporary dye on their dorsal fur. The bats will be held individually in a single-use bag for a sufficient time period (about two hours) for them to defecate so that guano can be collected. Time of capture will also be recorded.  Captures and recaptures will be recorded to estimate population size using the Lincoln Peterson method and movement from site to site. Abundance and species diversity will be computed and compared between sites that are heavily urbanized, moderately urbanized and not urbanized using a one-way ANOVA. While netting bats, a white tarp will be set up with a spotlight shining on it for insect collection. The insects will be collected using kill jars with approximately an inch of alcohol. Insects will be brought back to the lab and pinned/pointed accordingly to use for a reference collection in the guano analysis. The guano collected from the captured bats will be preserved in vials of 70% alcohol solution and analyzed separated by both species and site. Guano pellets will be examined individually under a dissecting microscope using a micro-dissecting probe. A ten-point grid will be used for qualitative analysis. The grid points will be spaced 2.5 mm apart. Insect specimens on each point will be identified to taxonomic Order and recorded using insect study guides and the reference collection. Three samples will be taken for each species of bat, or site captured if the species is caught in multiple locations. These procedures were used successfully in a recent NSF-REU sponsored investigation of bat diet composition in Alabama (Stone 2009). Prey selection between different bat species will be compared using a Chi-Squared Test or two way ANOVA (using species and site as main effects).The habitat, hydrological, land cover, and biological data can be integrated into a geospatial databases to show spatial patterns related to possible urbanization impacts.​

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