Mitigating the deceptive effects of smooth surfaces: subtle surface modifications can eliminate maladaptive drinking attempts by bats

The amount of artificial smooth surfaces in the environment increases continuously with urbanization on a global scale. There is growing evidence that smooth surfaces such as windows, solar panels and other objects can serve as sensory traps for many animal species. Artificial smooth surfaces can function as acoustic mirrors, disrupting echolocation of bats and consequently causing maladaptive behaviours such as drinking from and colliding with these surfaces. Therefore, investigating opportunities to mitigate the effects of artificial smooth surfaces is important from a conservation viewpoint. Here, we conducted a field experiment with bats, an ensonification experiment in the laboratory, and a computer simulation, in order to study the effect of mechanical surface modification on the acoustic characteristics of smooth surfaces. In the field experiment, we presented a horizontal smooth plate alone or with strings (diameters between 0.25–2.5 mm) and the behaviour of bats around the plate was video recorded. Bats significantly decreased the frequency of drinking events with increasing diameter of the strings. We also found an indication that a crossed pattern of the strings on the plate may be more effective than a parallel arrangement. The results of the ensonification experiment and the mathematical modelling revealed that a subtle modification of the smooth surfaces with long, linear thin objects can effectively modify the acoustic characteristics of smooth surfaces in general and thereby potentially change the behaviour of bats. Further investigations from sensory, behavioural and ecological viewpoints are proposed to better understand the impact of smooth surfaces on bats and the mitigation solutions that are needed. This research underscores the significance of exploring innovative approaches to minimize the negative impacts of urbanization on wildlife, highlighting the potential of practical interventions to promote coexistence between anthropogenic environments and threatened species.