Noise created by humans often disrupts normal animal or bird behaviors.  Just consider the consequences of human noise pollution. Disrupting ocean life is but one example.  Sadly, the negative outcomes are well documented in whales, dolphins, and other sea creatures.

A team from California Polytechnic State University and Boise State University wanted to understand the role of naturally occurring soundscapes on the behavior of other animals.

This team, led by ecologist Dylan Gomes, tested a hypothesis that natural sounds influence where bats and birds live and forage. Bats and birds were chosen because they are sound-dependent for critical behaviors such as communication, navigation, and hunting.

To test their hypothesis, the team created rushing whitewater sounds where gentle

Stream in Pioneer Mountains
Photo by Robert Crum on Dreamtimes

streams typically flow. They chose 60 study sites within the remote Pioneer Mountains of Idaho and set up the equipment.  Then they generated the noise, varying loudness and audio frequency.  

The results showed that both volume and pitch (frequency) impacted the bats’ and birds’ ability to go about their duties.  Pitch is important because it may mask or overlap with birdsong, as an example.  Consequently, subsequent increases in either decibel (for volume) or kilohertz (for pitch) caused both species to decrease their foraging behavior.  Some bats and birds even move away from the study sites.  The violent rushing river sounds appear to have been too distracting to continue life as usual.

Birds that stayed in the area were less efficient foragers. They harvested fewer insects.  In comparison, some bats were a bit more adaptable and made adjustments. They shifted from listening for their prey to using echolocation.  Despite this shift in behavior, foraging success still suffered.

More studies are warranted but if these species are this sensitive to natural sounds perhaps we have underestimated the impact of our noise-generating activities. 

For another example of naturally occurring noise impacts on a species, check out this earlier post about the waterfalls and the frogs.


Article at Cal Poly site –

 Research paper about this research –


@CalPoly   @BoiseState  

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