The Influencing Mechanisms Of Airport Noise On Foraging Behavior In Japanese Pipistrelle Bats

Anthropogenic noise is changing the soundscape of ecosystems at an unprecedented rate and scale,posing a threat to the survival and reproductive success of animals and humans.Consequently,anthropogenic noise is recognized as an emerging environmental pollutant.Previous researches have focused on direct effects of anthropogenic noise on foraging behavior in various animals through noise masking,physiological stress,or distraction.However,the indirect impacts of anthropogenic noise on foraging activity in animals are widely neglected.Bats are typically nocturnal animals that rely primarily on echolocation for spatial orientation and foraging,making them an ideal taxon for the study of noise pollution.For the first time,we used Pipistrellus abramus as a model to disengage the influencing mechanisms of airport noise on foraging behavior from the perspective of insect prey.Pipistrellus abramus frequently initiates foraging activities in Nanchong Gaoping Airport.We monitored foraging activities of these bats at 11 sites around the runway.We quantified noise level and spectra,aircraft activity,insect abundance,habitat type,nightly temperature,wind speed,and moon phase per site.To examine the influence of truck and aircraft noises on bat foraging and insect abundance,we performed playback experiments at the most common foraging site exploited by P.abramus.We collected faecal pellets from P.abramus and identify their dietary compositions using fecal DNA sequencing.Playback experiments in the wild and laboratory were conducted to determine whether P.abramus and insect prey(Drosophila melanogaster,Aedes albopictus,and Cnaphalocrocis exigua)would exhibit avoidance response to truck and aircraft noises.The level of airport noise was negatively associated with the number of passes and feeding buzzes in P.abramus based on our field survey,although there was no marked spectral overlap between airport noise and their echolocation pulses.The number of bat passes and feeding buzzes declined with the presence of aircraft.The duration and spectral parameters of echolocation pulses emitted by P.abramus were dependent on airport noise level,aircraft activity,and habitat type.Field playbacks revealed that truck and aircraft noises induced a marked decline in the number of bat passes and feeding buzzes compared with silence control.The number of bat passes and feeding buzzes were also predicted by insect abundance and nightly temperature.Path analysis confirmed that truck and aircraft noises not only exerted direct effects on the number of passes and feeding buzees in P.abramus,but also exerted indirect effects on their foraging activities via influencing insect abundance.Playback experiments in the laboratory demonstrated that P.abramus showed no marked differences in body surface temperature and the number of crawling under silence control versus noise playbacks,but the number of echolocation vocalizations was significantly reduced during playback of aircraft noise.The diet of P.abramus was composed of four orders of insects according to fecal DNA sequencing,including Diptera,Ephemeroptera,Lepidoptera,and Coleoptera.The mosquitoes from the families Chironomidae and Culicidae were the most common prey consumed by P.abramus.Despite the nonsignificant role of truck noise,we found that the number of crawling and flight in D.melanogaster,A.albopictus,and C.exigua increased following playbacks of aircraft noise.These insects also showed speciesspecific responses to playback stimuli.Taken together,these results provide evidence that airport noise can effect foraging behavior of P.abramus,even if there is no spectral overlap between airport noise and ultrasonic pulses.The airport noise can affect foraging behavior of P.abramus via reducing the abundance and activities of insect prey.The results support the prey avoidance hypothesis proposed by us and suggest that airport noise has indirect effects on foraging behavior of bats.The direct effects of airport noise on foraging behavior of P.abramus may be attributed to physiological stress instead of noise masking and reduced attention.This study broadens the current knowledge of the mechanisms behind the impacts of noise pollution on foraging behavior in bats,and provides implications for bat conservation and management in the context of global noise pollution.