| Popis: |
Rivers and their associated floodplains are natural wildlife corridors used by a wide range of animal species. Most British rivers in both rural and urban areas have been significantly affected as a result of drainage, flood defence structures, urban development and direct habitat loss. This has, in some cases, fragmented the river corridor and affected the structure and function of the riparian zone. As landscape-scale conservation schemes aim to restore the ecology of rivers, I consider what affect the quality of the riparian zone (an area where the river channel, bank and flood plain interact) has on the foraging and activity of important riparian users, British bats, and assess their relevance as bioindicators of ecosystem health. A matched pairs design was used to test the effect of 'undisturbed' (high quality) and 'disturbed' (lower quality) riparian zones based on riparian width, habitat complexity, connectivity, and surrounding land use, on bat activity. In general, wider and more complex riparian zones did not show sign ificantly more bat activity overall, though exhibited significantly greater foraging activity expressed by the number of feeding buzzes recorded. However, species-specific responses showed that Pipistrellus pygmaeus and Myotis spp. (probably mainly Myotis daubentonil) were influenced by the quality of the riparian zone more so than known habitat generalists, such as P. pipistrellus. Small differences in the complexity and width of the riparian zone positively affected the foraging and activity of P. pygmaeus, whereas the presence of wider stands of wet woodland positively affected the foraging and activity of Myotis spp. Broader landscape features and the availability of insect prey also affected the activity of two sympatric species, P. pipistrellus and P. pygmaeus. Both species were positively associated with the presence of urban habitat within a 2 km radius of survey sites and aquatic invertebrates, and showed niche differences related to known dietary preferences. The association with invertebrate abundance may make Pipistrellus bats potential bioindicators of riverine health. Pipistrellus bats select riverine habitats that are associated with urban areas, which may indicate a dependency on rivers in urbanised areas. The composition of the riparian zone and floodplain habitat affects the foraging and activity of riparian specialist British bats and should be considered when designing landscape-scale conservation schemes that include British rivers. |
