Navigating light and noise: Behavioural underpinnings of bat responses to anthropogenic disturbance

More than 50% of bat species have unknown or declining population trends, often driven by human-induced rapid environmental change. Efforts to safeguard these species are hindered by knowledge gaps regarding the effects of anthropogenic stressors on the behaviour of wild bats. Artificial Light At Night (ALAN) and anthropogenic noise represent two widespread environmental stressors to which many bats are sensitive because they are nocturnal, and echolocating species depend heavily on sound for both communication and navigation. Here, we review evidence for the behavioural impacts of ALAN and anthropogenic noise across 146 studies. First, we summarise underlying mechanisms via which these stressors can affect bat behaviour. We then evaluate their impacts across contexts (foraging, drinking, commuting, emergence and within roost), considering their (a) individual and (b) interactive effects. Overall, both stressors were associated with avoidance of disturbed areas and changes in foraging behaviour, whereas only ALAN consistently altered emergence behaviour. Clutter-adapted species were generally more sensitive, however, substantial behavioural plasticity was evident, and generalisations were limited by methodological variation across studies. Most studies relied on coarse activity metrics (58%), few examined in-roost behaviour (7%), and only 4% quantified both illuminance and noise amplitude. Although most studies did not explicitly test for interactive effects, available evidence suggests non-additive outcomes. We advocate for increased attention to within-roost behavioural responses and the adoption of a multistressor framework. Priority research directions include integrating behavioural and physiological measures and evaluating the fitness consequences of behavioural change. Together, these efforts will strengthen conservation strategies and inform research in other sensitive taxa.