Influence Of Urban Expansion on Bat Diversity Roosting Patterns and Foraging Behaviour in Metropolitan Areas

Abstract

Urban growth is one of the main contributors to biodiversity losses around the world, but their influence on bat communities is still not well known within metropolitan environments. In this study, bats' diversity, roosting preference and foraging behaviour were assessed in five different habitats from a gradient ranging from urban to rural, in one of the largest metropolitan regions. Acoustic sampling took place in 45 different sites during 24 months, using full spectrum bat detectors. A total of 16 different species of bats were identified, showing that species richness decreases significantly from peri-urban reserves (13 species, Shannon index H′= 2.18) to urban core (3 species, H′= 0.62; p<0.001). Roost surveys have demonstrated a change from natural structures (hollow trees and cracks of rocks) in less urbanized zones to artificial ones (building cracks and bridges). The foraging behavior, measured by echolocation pass rates, showed that foraging behavior was highest in green corridors (47.3 ± 6.8 passes/hr) but lowest in urban core (18.4 ± 3.1 passes/hr). The regression analysis found artificial light at night and noise as significant negative predictors of bat activity (R² = 0.74). This study proves that urbanization is filtering out bats, retaining only ecologically plastic generalists while habitat specialists are being excluded from the ecosystem. Bat species richness and activity are high where there is more greenery such as riparian corridors and trees. From this study, it is evident that it is necessary to reduce light and noise pollution, and conserve green space to ensure the survival of diverse bat populations. These approaches will contribute significantly towards biodiversity and maintenance of foraging habitats in urban environments.