Through the magnifying glass: Untangling fine-scale foraging choices of bats between cropland and adjacent dry grassland

Abstract

Insectivorous bats forage opportunistically on ephemeral prey. However, fluctuating resources in open agricultural landscapes pose challenges, especially during energetically demanding periods such as lactation. While protected semi-natural dry grasslands provide more stable conditions compared to unpredictable croplands, it remains unclear how bats choose between these two habitats when they are adjacent. We investigated fine-scale foraging choices of bats by comparing feeding intensity on a short distance between cropland and adjacent dry grassland. We accounted for interaction effects of agricultural management and season, reflecting resource availability and energetic requirements. Data were obtained through repeated acoustic monitoring of 25 pairs of crop and grassland in different agricultural areas in Germany. In early summer, when energy demands peak, open-space bats showed higher feeding intensity on dry grasslands than on conventionally managed cropland. A similar pattern emerged for edge-space bats when grasslands had more shrubs and trees. Conversely, bats preferred high-quality organic cropland over adjacent grassland in heterogeneous landscapes. In late summer, the foraging choices were generally less pronounced. By examining interaction effects of landscape and seasonal variables on feeding intensity, we revealed bats’ small-scale selections of habitats offering comparatively higher foraging value within a given spatial and temporal context, especially during energetically critical periods. Understanding bats’ seasonal flexibility in habitat selection is crucial for developing effective and future-oriented conservation strategies. We emphasize the importance of incorporating alternative habitats such as dry grasslands as potential foraging refuges into conservation planning to enhance bat resilience amid ongoing agricultural intensification and environmental changes.