Our Loan Program for students has once again yielded remarkable results in the field of environmental research.
Rani Davis, a talented researcher from the University of Queensland, conducted a ground-breaking study investigating the impact of Artificial Light at Night (ALAN) on insectivorous bat activity in Brisbane, Australia.
Through our support, Rani was equipped with Anabat Swift and Chorus detectors to carry out her research, which has provided essential insights into the behaviour of bat species in response to artificial lighting.
Summary of Findings
Rani's research was the first in Australia to investigate how the flight activity of two insectivorous bat species changed with increasing distance from artificial light sources. The findings and implications of her study are summarized as follows:
1. Light-Sensitivity of Slower-Flying Bat Species
As predicted, Rani observed that ALAN negatively impacted the activity of the slower flying bat species, M. australis. This confirmed the species' light-sensitivity and was in line with previous studies (Haddock et al., 2019a, 2019b).
2. Extent of ALAN's Impact on M. australis
Contrary to expectations, the negative effect of ALAN on M. australis did not diminish with increasing distance from the light source. The species showed reduced activity across all distance steps on the treatment transects (0, 10, 25, and 50m), indicating that the impact of ALAN on M. australis likely extends beyond 50m.
3. Attractant Effect on Faster-Flying Bat Species
In contrast, the faster-flying species, A. australis, exhibited increased activity near the position of the streetlight (0m). This suggests that A. australis may exploit artificial lights as foraging resources, but the attractant effect is limited to a very short distance. Similar effects were reported in Europe for light-exploitative bat species (Azam et al., 2018).
4. Implications for Conservation and Lighting Policies
Rani's study has critical implications for conservation efforts and urban lighting policies. Simply reducing the intensity of artificial lights may not be sufficient to protect very light-sensitive species like M. australis, as they were still negatively affected even at low illuminance levels. Instead, Rani recommends minimizing light spill through improved lighting designs, which can be achieved by mounting lights closer to the ground, adding luminaire shields, or using directional lighting (DEE, 2020; Gaston et al., 2012; Schroer & Hölker, 2017).
Rani Davis's research represents a significant contribution to understanding the effects of artificial lighting on insectivorous bat activity in Brisbane. By identifying the light-sensitivity of certain bat species and exploring the extent of ALAN's impact, her study highlights the need for thoughtful urban lighting designs that consider the well-being of wildlife. We commend Rani's dedication and applaud her for presenting her findings last month at the Ecological Society of Australia Annual Conference (ESA 2023) held in Darwin, NT. Through our Loan Program, we are delighted to support young researchers like Rani, who are driving positive change in environmental science and conservation.
References (in order of appearance)
Haddock, J. K., Threlfall, C. G., Law, B., & Hochuli, D. F. (2019a). Light pollution at the urban forest edge negatively impacts insectivorous bats. Biological Conservation, 236, 17–28. https://doi.org/10.1016/j.biocon.2019.05.016
Haddock, J. K., Threlfall, C. G., Law, B., & Hochuli, D. F. (2019b). Responses of insectivorous bats and nocturnal insects to local changes in street light technology: Insectivorous bats and street light technology. Austral Ecology, 44(6), 1052–1064. https://doi.org/10.1111/aec.12772
Azam, C., Le Viol, I., Bas, Y., Zissis, G., Vernet, A., Julien, J.-F., & Kerbiriou, C. (2018). Evidence for distance and illuminance thresholds in the effects of artificial lighting on bat activity. Landscape and Urban Planning, 175, 123–135. https://doi.org/10.1016/j.landurbplan.2018.02.011
Gaston, K. J., Davies, T. W., Bennie, J., & Hopkins, J. (2012). Reducing the ecological consequences of night‐time light pollution: Options and developments. Journal of Applied Ecology, 49(6), 1256–1266. https://doi.org/10.1111/j.1365-2664.2012.02212.x
Hooker, J., Lintott, P., & Stone, E. (2022). Lighting up our waterways: Impacts of a current mitigation strategy on riparian bats. Environmental Pollution, 307, 119552. https://doi.org/10.1016/j.envpol.2022.119552
DEE. (2020). National light pollution guidelines for wildlife. Department of Environment and Energy, Australian Government.
Schroer, S., & Hölker, F. (2017). Light pollution reduction. In R. Karlicek, C.-C. Sun, G. Zissis, & R. Ma (Eds.), Handbook of Advanced Lighting Technology (pp. 991–1010). Springer International Publishing. https://doi.org/10.1007/978-3-319-00176-0_43
Rani Davis presenting the
Swift deployed with
Chorus deployed on
Chorus making friends in