Shift in diet composition of a riparian predator along a stream pollution gradient.

Terrestrial insectivores in riparian areas, such as spiders, can depend on emergent aquatic insects as high-quality prey. However, chemical pollution entering streams from agricultural and urban sources can alter the dynamics and composition of aquatic insect emergence, which may also affect the riparian food web. Few studies have examined the effects of stressor-induced alterations in aquatic insect emergence on spiders, especially in terms of chemical pollution and diet composition.

Increased bat hunting at polluted streams suggests chemical exposure rather than prey shortage.

Streams and their riparian areas are important habitats and foraging sites for bats feeding on emergent aquatic insects. Chemical pollutants entering freshwater streams from agricultural and wastewater sources have been shown to alter aquatic insect emergence, yet little is known about how this impacts insectivorous bats in riparian areas. In this study, we investigate the relationships between the presence of wastewater effluent, in-stream pesticide toxicity, the number of emergent and flying aquatic insects, and the activity and hunting behaviour of bats at 14 streams in southwestern Germany.