Factors Determining the Abundance of Vespertilionid Bats in Britain: Geographical, Land Class and Local Habitat Relationships

Abstract

1. Transect surveys of foraging bats in a stratified sample of 1030 1-km squares in Britain were used to compare bat abundance in different land classes. 2. Bat abundance remained constant from early to late summer but varied significantly between land classes. Increased ambient temperatures caused increased local abundance of bats. High abundance occurred within arable and pastural land class groups in the south, while low abundance occurred in arable, marginal upland and upland land class groups in the north. 3. Regression analyses identified a significant negative gradient in bat abundance on a south-north axis in Britain and also on a west-east gradient within a transect across North Wales and the English Midlands. 4. Regression analyses further outlined significant relationships between bat abundance and habitat availability within seven land class groups. Habitats included in the models were similar for each land class group. In general, bat abundance was positively related to the availability of woodland, vegetation corridors, lacustrine and riverine habitats and negatively related to the availability of arable land. 5. The models quantifying the relationship between bat abundance and habitat availability presented in this paper provide a basis for predicting the suitability of sites for foraging bats and a tool for further research to test the hypotheses relating the impact of past and future large-scale land-use change on vespertilionid bat populations in Britain.