Turn down for what? For bats, with their sensitive hearing and reliance on sound to find food and get around using echolocation, unnecessary or unfamiliar noises can cause extra problems.
08.27.25
By Alyson Brokaw
When most of us think about pollution, we imagine oil spills in the middle of the ocean, radioactive waste leaking from power plants, or the thick, hazy smoke from burning wildfires. Unfortunately, human impacts on the environment and animals are not just limited to these physical and chemical forms of pollution. Regular activities like leaving the porch light on, driving along roads, rocking out at music festivals, or cheering with the crowd at a sporting event can all contribute to a different, more intangible type of pollution by altering the natural light and soundscapes of the environment.
Noise pollution is harmful to all sorts of animals, including humans. For bats, with their sensitive hearing and reliance on sound to find food and get around using echolocation, unnecessary or unfamiliar noises can cause extra problems.
Planes, Trains, and Automobiles
One major source of noise pollution is our transit system—highways, driveways, and airplane runways. A recent meta-analysis of data from 60 bat species worldwide suggests that noise associated with transportation and urban environments have the largest negative impact on bats. Lab and field data support these findings. In lab settings, mouse-eared bats (Myotis myotis) avoided areas of a flight room where traffic noise was played and pallid bats (Antrozous pallidus) took two to three times longer to capture prey when exposed to traffic noises compared to silent controls.
Free-ranging bats also change behavior in response to transportation noise. Traffic noise broadcast in natural areas in the United Kingdom resulted in reduced bat activity across five different species of bat, including the greater horseshoe bat (Rhinolophus ferrumequinum) and the soprano pipistrelle (Pipistrellus pygmaeus). Soprano pipistrelles also showed reduced foraging activity during and after playbacks, with noise affecting bats as much as 20 meters away (65 feet). Airport noise also negatively impacts bat activity, with Japanese pipistrelle bats (Pipistrellus abramus) reducing flight and foraging activity near airport runways.
Other sources of loud noises, such as concerts or music festivals may also have impacts on bats. In the Negev desert, bats were less efficient at drinking water after loud music was played and avoided foraging areas where music was being broadcast. In the U.K., loud music played along forest edges reduced activity for noctules and serotine bats (Nyctalus/Eptesicus spp.), but not other species like mouse-eared bats (Myotis).
Adapting to the Racket?
As auditory specialists, bats frequently face challenges regarding noise and some bats may be more adept at the task than others.
Noise is a natural part of the environment—from rushing rivers to wind rustling through the trees. As auditory specialists, bats frequently face challenges regarding noise and some bats may be more adept at the task than others.
Gleaning bats, who listen for prey-generated sounds (like insect footsteps) may be particularly vulnerable to anthropogenic noise. Traffic and other human-made sounds can mask these subtle cues, interfering with the bats’ ability to locate prey. Even species otherwise tolerant of urban environments can be negatively impacted by noise. In Chicago, lower frequency echolocators such as big brown bats (Eptescius fuscus), silver-haired bats (Lasionycteris noctivagans) and evening bats (Nycticeius humeralis) were significantly less likely to be in areas with loud noise, and the negative impacts of noise even outweighed potential benefits like proximity to water. This is also consistent with work that showed up to a 70 percent reduction in activity of low frequency bats (echolocation calls less than 35 kHz) near gas compressor stations compared to quieter sites.
When faced with noisy environments, some bats will adjust their echolocation calls to try and adapt. Mexican free-tailed bats (Tadarida brasiliensis) flying near gas compressor stations modified their echolocation calls, producing longer and more narrow frequency calls, which could also impact their ability to locate and capture prey. Within species, individuals may also vary in their ability to cope with noise. Pale spear-nosed bats (Phyllostomus discolor) trained on a discrimination task (used to detect the difference between two or more stimuli) and tested in different experimental noise treatments adjusted their echolocation calls in response to the noise, but some individuals were better able to cope than others.
It is also important to note that bats have to listen for more than just echolocation calls or the sounds of insects moving. Bats use a variety of social calls to communicate with each other, including courtship songs, aggressive buzzes and pup isolation calls. Although it is currently unclear how anthropogenic noise may impact bat social communication. Understanding how bats respond to all types of environmental change, including sensory changes like light and noise, is more important than ever. And while scientists have worked hard to measure the potential impacts on bats, there are still gaps in our knowledge, with most known work focused on temperate species in the United States and Europe. Bats do a lot of important things for us and the environment, from pollination to insect control. By filling in our knowledge gaps, we can better protect bat populations and ensure they continue their ecological roles for years to come.
Alyson Brokaw, PhD is a behavioral ecologist, sensory biologist and science communicator. When not talking about bats, she can be found cuddling with her dog, exploring her local Pennsylvania woods and throwing plastic on the ultimate frisbee field.
