The effect of artificial lighting on bats in Britain
Thesis or dissertation
University of Exeter
Artificial light pollution is increasing on a global scale at an annual rate of 6 per cent. Recent advances in artificial lighting technology are being developed at a faster rate than the ongoing replacement of conventional street lighting. This new technology is consumer driven for a broad band light spectrum, suitable for human vision, but little research has been conducted on its ecological impacts. Although it is known that light pollution can have major adverse affects on a wide array of species and ecological systems, research into the extent of these impacts is in its infancy. The most likely species to be adversely affected are those adapted to dark environments. Due to this, the focus of this thesis is on bats, a common nocturnal taxa in the UK, and the affects of artificial lighting on contrasting species within the taxa. In this thesis, two approaches were taken; a large scale observational landscape investigation of the impacts of artificial lights (street lights) under current environmental conditions; and a small scale experimental investigation of the responses of bats to three lighting treatments: dark, UV-LED lighting, and filtered UV-LED lighting. In the former investigation, the focus is on a generalist species; Pipistrellus pipistrellus and a specialist genera; Rhinolophus. In both investigations the activity of P. pipistrellus, the most common bat in the UK, did not differ significantly at dark compared to artificially light locations. However, in the landscape study, the rate of foraging was 35% higher in dark locations (0.03 passes per detector night ± SE 1.17) compared to at street lit locations (0.02 ± SE 1.29; P = 0.027). In contrast, the activity of Rhinolophus spp. was 79% higher at dark locations (0.21 ± SE 1.00) compared to at street lit locations (0.04 ± SE 1.00, P = 0.052). No significant effects were found in the experimental study, possibly due to the high variability of bat activity, insufficient replicates and insufficient differences between the light types. The landscape study confirms that increased artificial lighting will have adverse effects on Rhinolophus spp., limiting the available habitat in the landscape for commuting and foraging. In contrast, P. pipistrellus activity was not affected by artificial lighting. However, reduced foraging was found in these locations, possibly due to altered insect composition at artificially lit locations, which may have negative indirect affects for this species. These results highlight the wider importance for all species of the ecological impacts of artificial lighting and contribute to the growing body of research in this area which discourages the continued trend for illuminating naturally dark environments.
Masters by Research in Biological Sciences