Experimental noise and light pollution alter prey detection in a nocturnal bird of prey.

Urban expansion has led to ever increasing noise and light pollution, which impairs the audio-visual perception of wild animals and drives changes in key activities and behaviours. Nocturnal predators may be especially affected in detecting prey, with potentially dramatic consequences for their fitness. However, the combined effects of noise and light pollution on predator performance are still mostly unstudied. We experimentally exposed tawny owls (Strix aluco), nocturnal acoustic raptors, to traffic noise and artificial light. We provided both visual and acoustic prey cues to assess potential non-additive effects among multiple sensory stressors on the ability to detect prey. We found that, in control conditions, owls responded equally to both acoustic and visual prey cues. In contrast, noise and light individually decreased owls' ability to locate acoustic, but not visual, prey cues. When owls were exposed to noise and light combined also visual detection worsened, but not beyond the additive expectation. Conversely, the presence of light seemingly buffered the negative impact of noise on acoustic detection, suggesting an antagonistic interaction. Our findings show that both anthropogenic noise and light affect the hunting behaviour of a nocturnal avian predator, but with a stronger effect on acoustic than visual detection, suggesting that the magnitude of their disruptive impact might depend on the type of prey cue. This implies that sensory pollution might lead to increased reliance on sight-oriented hunting strategies. Importantly, our study shows that the co-occurrence of noise and light can have complex and unexpected impacts on behaviour, underscoring the importance of examining sensory pollution in a multimodal context.