Urban bats show dietary flexibility in aquatic arthropod consumption at urban and rural waterbodies

Abstract

Urban waterbodies are critical for biodiversity and provide feeding grounds for insectivorous bats. Yet, how urbanisation affects bats' food choices at urban waterbodies and the role of emergent aquatic arthropods remain poorly understood. We compared the diet of three urban bat species – Vespadelus vulturnus, Chalinolobus gouldii,and Myotis macropus – in southeastern Australia that vary in their consumption of emergent aquatic arthropods. Our aims were to assess 1) their dietary composition, 2) the proportion of aquatic compared to terrestrial arthropods in their diet at urban and rural waterbodies, and 3) the proportion of consumed versus available arthropods. We analysed faecal pellets from V. vulturnus (n = 38 individuals), C. gouldii (n = 38), and M. macropus (n = 19) alongside arthropod samples from light traps. High-throughput sequencing techniques revealed 12 arthropod orders in the diet of V. vulturnus, seven in C. gouldii, and three in M. macropus. Chalinolobus gouldii and V. vulturnus shared some prey arthropod families, but M. macropus fed on distinct families. All three bat species consumed arthropods with aquatic larval stages, with the most in M. macropus (32.4%) and least in C. gouldii (8.0%). Vespadelus vulturnus also consumed a significant amount of aquatic arthropods, with this proportion higher in rural than urban sites. Molecular Operational Taxonomic Units (MOTUs) of Lepidoptera and Diptera dominated the diet of all three bat species, despite the availability of more arthropod orders found with light trapping. Our results confirm the role of waterbodies as foraging grounds for urban bats, but also emphasize the importance for supporting both aquatic and terrestrial arthropods in urban areas to provide diverse arthropod prey to bats.