Patterns of Bat Distribution and Foraging Activity in a Highly Urbanized Temperate Environment

Abstract

Understanding how to manage biodiversity in urban areas will become increasingly important as density of humans residing in urban centers increases and urban areas expand. While considerable research has documented the shifts in biodiversity along urbanization gradients, much less work has focused on how characteristics of dense urban centers, effectively novel environments, influence behavior and biodiversity. Urban bats in San Francisco provide an opportunity to document changes in behavior and biodiversity to very high-density development. We studied (1) the distribution and abundance of bat foraging activity in natural areas; and (2) characteristics of natural areas that influence the observed patterns of distribution and foraging activity. We conducted acoustic surveys of twenty-two parks during 2008–2009. We confirmed the presence of four species of bats (Tadarida brasiliensis, Myotis yumanensis, Lasiurus blossevillii, and M. lucifugus). T. brasiliensis were found in all parks, while M. yumanensis occurred in 36% of parks. Results indicate that proximity to water, park size, and amount of forest edge best explained overall foraging activity. Proximity to water best explained species richness. M. yumanensis activity was best explained by reduced proportion of native vegetation as well as proximity to water. Activity was year round but diminished in December. We show that although bats are present even in very densely populated urban centers, there is a large reduction in species richness compared to that of outlying areas, and that most habitat factors explaining their community composition and activity patterns are similar to those documented in less urbanized environments.

Need for multiscale planning for conservation of urban bats

“…At broad scales, patterns, and distributions of habitat characteristics may influence the importance of characteristics at finer scales (Turner & Gardner ). Urban bats may select forest edges for foraging (Krauel & LeBuhn ). Perhaps open vegetation at larger scales is indicative of increased forest edge and thus increased foraging habitat.…”

“…). Many bat species can live in urban spaces (Kurta & Teramino ; Gehrt & Chelsvig ; Krauel & LeBuhn ) and directly or indirectly provide ecosystem services to such environments (Kunz et al. ); thus, creating, managing, and monitoring bat habitat in urban environments should be a conservation priority.…”

Life in a northern town: rural villages in the boreal forest are islands of habitat for an endangered bat

“…, Coleman and Barclay , Threlfall et al. , Russo and Ancillotto , Jung and Threlfall , Krauel and LeBuhn ). This decline has been attributed to reduced prey abundance (Geggie and Fenton , Avila‐flores and Fenton , Threlfall et al.…”

“…, Lausen and Barclay , Johnson et al. , Coleman and Barclay , Krauel and LeBuhn ). However, white‐nose syndrome (WNS) has killed several million little brown bats in northeastern North America since 2006 (Frick et al.…”

“…), and this may be particularly true in urban environments. Wetlands, ponds, lakes, and rivers may facilitate the persistence of bats in developed areas, where foraging habitat is otherwise lacking (Krauel and LeBuhn , Straka et al. ), and where insect biomass may be reduced (Threlfall et al.…”