Whitewater River Loud Noise Affects Hunting of Birds While Bats Switch to Echolocation

New research recently found birds and bats frequently avoid environment that's swamped with loud noise coming from the whitewater river.

Science Codex report specified that, according to the first author on the paper, Dr. Dylan Gomes, naturally-loud environs have been greatly neglected in ecological studies.

Gomez, a recent PhD graduate of Boise State University added, they, through the research, aimed to test hypothesis that strong natural noise can shape both distributions and behaviors of animals by experimentally broadcasting whitewater river noise at a huge scale.

The researchers even had to transport tons of gear through "roadless" territory to install solar-powered speaker arrays in about 50 percent of their 60 sites in Idaho's Pioneer Mountains where they observed bat and bird populations for two summers.

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Whitewater River Noise

The speaker arrays were placed along with riparian sites, filling every bubbling brook with a rushing whitewater river's auditory experience.

In their study, Phantom rivers filter birds and bats by acoustic niche, published in Nature Communications, the researchers took advantage of their experimental method to broadcast both the river noise's realistic reproductions and the river noise itself, that had been lifted upwards in frequency to understand how the noise resulted in changes in animal quantities.

The predominant hypothesis for the reason a lot of animals are avoiding noise is called "masking." This takes place when noise is overlapping in frequency, commonly perceived as pitch, with a biological cue or signal.

Through broadcasting of different frequencies' noise, Boise State University's Dr. Jesse Barber, the study's senior author said, they hoped to analyze the role that masking of essential sounds like birdsong for one, is playing in the avoidance of noisy environments.

The researchers discovered that overlap between-song frequency and background noise projected bird decreases until acoustic environments turned out about as loud and noisy as a highway, at which point other forces like not being able to hear prey and predators, likely turned out to be more vital.

Birds That Stayed in Naturally-Loud Sites

To examine foraging in birds that stayed in naturally loud sites, the researchers set out hundreds of caterpillar decoys across their sites of research. The said decoys were made of clay.

By carefully evaluating the mark types left by predators in the clay, the researchers discovered that louder noise meant less hunting by birds.

It also means that after controlling for the fact that lesser birds were discovered in loud environments, birds were less efficient when it comes to visually hunt for the silent, decoy caterpillars in the presence of noise.

This is different from the difficulty humans can experience when they are attempting to listen to a friend talk while a muted television is turned on, with divided attention.

Study in Bats

To understand how bats that stayed in noisy areas managed, the research team positioned two scavenging puzzles to solve.

The first puzzle was called a "robo-moth" that attracted bats with its insect-like wing beats. Meanwhile, the second puzzle was a speaker that played mixed tape containing katydid and cricket calls and sounds of insect walking.

In a similar report, Phys.org specified that for nearly 150 nights of collecting data, the researchers discovered that, as the world produces louder noise, some bats are switching from listening for sounds of prey to the use of echolocation.

Such a behavioral switch, according to Dr. Gomes, is likely driven by prey calls and footsteps which the river noise and this kind of problem-solving possibly explain the reason some bats can stay close to the disturbance of raging whitewater river.

A related report on bat echolocation is shown on Smithsonian Channel's YouTube video below: