Soundscapes of the Upper Amazon: Seasonal Activity Patterns of Insectivorous Bats in Cordillera Escalera, Peru

Abstract

Bats, the second most diverse group of mammals, play essential ecological roles in insect control, pollination, and seed dispersal. In Peru, insectivorous bats remain poorly studied, particularly in high-elevation rainforest ecosystems of the upper Amazon region. This study used passive acoustic sampling to examine the nocturnal activity patterns of insectivorous bats in the Cordillera Escalera Regional Conservation Area, San Martín, Peru, during the wet and dry seasons of 2024. We evaluated activity and hourly activity patterns at both community and species levels to assess seasonal variation in temporal behavior. Ten insectivorous bat species were recorded. Overall bat activity was substantially higher during the wet season than the dry season, with some variation in species-specific responses. High-flying species exhibited increased activity during the wet season, whereas low-flying species maintained or intensified their activity during the dry season. The wet season was characterized by higher temporal synchrony, whereas the dry season was characterized by greater temporal partitioning. Most species exhibited unimodal activity patterns that peaked early at night, but some species displayed bimodal patterns, suggesting temporal segregation related to foraging strategies and habitat structure. This study represents the first assessment of hourly activity patterns of insectivorous bats in the upper Amazon montane rainforests and establishes a baseline for long-term acoustic sampling aimed at understanding how seasonal and environmental variability shape bat temporal niches.