Bat diversity in the Metropolitan Area of Asunción (Paraguay) and complementarity between mist-netting and acoustic monitoring

Abstract

Despite the rapid expansion of urban areas, their role in shaping Neotropical bat assemblages remains poorly understood. In Paraguay, no formal inventory has been conducted for the Metropolitan Area of Asunción. This study aimed to characterize bat diversity and evaluate the complementarity of mist-netting, active and passive acoustic monitoring. Sampling was conducted at 15 sites over 90 nights in the Metropolitan Area of Asunción using a standardized design integrating capture-based and acoustic survey techniques. A total of 26 bat species were recorded, representing 43% of the 60 species currently reported for Paraguay. Acoustic monitoring detected 18 species, whereas mist-netting recorded 15. Sampling completeness was higher for acoustic methods, particularly passive monitoring, while mist-netting underestimated species richness. Each method detected different components of the assemblage, indicating complementarity between capture-based and acoustic approaches. In contrast, acoustic methods showed a high degree of overlap in species composition, differing by only one species, suggesting limited additional benefits of their combined use for species detection. The detections of Myotis riparius through both mist-netting and acoustic monitoring, and Nyctinomops macrotis exclusively through acoustic data, represent a significant finding, as these species had not previously been reported for the study area. The integration of mist-netting and acoustic monitoring improved the characterization of urban bat assemblages. This work provides the first inventory of bats for Asunción and establishes a baseline for future research and monitoring efforts in Paraguay.