Insectivorous bats alter their flight and feeding behaviour at ground‐mounted solar farms

Efforts to mitigate the climate crisis result in a green‐green dilemma: the development of renewable energy technology is required worldwide to reduce greenhouse gas emissions but can have negative impacts on biodiversity. Impacts are being documented for wind farms, but effects of solar farms (photovoltaic power stations) on habitat use of vertebrates remain extremely poorly known. Using insectivorous bats as a biological model for high trophic levels, we tested whether the presence of ground‐mounted solar farms affected flight and feeding behaviour. We assessed behaviour using three‐dimensional flight path reconstruction systems from echolocation calls, via standardised paired sampling of 16 control and 16 solar farm (treatment) sites. We quantified bat flight and feeding behaviour as flight speed, sinuosity of flight trajectories, and the probability of emission of feeding buzzes (acoustic signatures of prey capture attempts), and demonstrated that feeding was characterised by slow, sinuous flight with feeding buzzes. We recorded 15,273 three‐dimensional bat positions, resulting in 1317 flight trajectories. We found strong behavioural responses to ground‐mounted solar farms in two of three bat guilds and five of seven taxa. Specifically, bats shifted their flight towards faster (+10 to +44%) and straighter trajectories (+33%) with lower probability of prey capture attempts (−18 to −39%) at solar farms. Since these changes in flight features are explicit indicators of a decrease in bat feeding behaviour, the implementation of ground‐mounted solar farms is likely to result in reduced feeding habitat quality for bats. Synthesis and applications: The negative effects of solar farms on bat flight and feeding behaviour should be considered when solar energy projects are planned. Research is needed to understand the mechanisms underlying the effects; for example, shading underneath solar panels may reduce plant biomass and therefore insect prey availability. Until exact mechanisms are identified, efforts should be made, first to avoid building solar farms on sites with great feeding potential for bats, and second to offset residual effects by improving the surrounding land and/or solar farms to provide better foraging opportunities. In this way, populations of bats can be supported alongside the generation of renewable energy. Résumé Les efforts d'atténuation de la crise climatique génèrent un dilemme écologique: le développement d'énergies renouvelables est n