Human Sounds Affecting Wildlife

A mule deer buck crosses the road in front of traffic along College Street in Bozeman in September 2011.

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Wild animals don’t like living near high-noise areas any more than people do, yet, while people can close their doors, animals have no alternative but to leave.

Now, a Bozeman-based scientist has created a computer model that can predict the ways human-caused noises invade natural environments, helping scientists learn how increasing development could damage ecosystems.

Sarah Reed of the Wildlife Conservation Society said most sound-modeling programs she tried were not only expensive but were developed for cities, where the racket of jackhammers and traffic bounces off hard buildings, or where the roar of airplanes rattles kitchen windows. She could find no models that considered the sound-absorbing characteristics of trees and grasses.

Plus, the programs focused only on the sound frequencies and volumes heard by people.

“A number of species rely on sounds that are 20 decibels below the human threshold,” said Kurt Fristrup, National Park Service scientist in the Natural Sounds and Night Skies Division.

So Reed and two other scientists developed a model that could be added to common data-mapping software. It allows users to add layers for different terrain, vegetation and even weather factors.

Then she gave it away for free.

Since 2011, hundreds of users from more than 25 countries — including Forest Service and Bureau of Land Management scientists, recreational planners and community organizations — have downloaded the program, Reed said. One graduate student may even carry it a step further by meshing it with Google Earth.

Scientists at the Natural Sounds and Night Skies Division have used Reed’s program, plus two others, to help NPS managers make policy decisions.

“It’s easier to get the data in and export it to maps to give decision-makers and the public more information,” Fristrup said.

The NPS is required to preserve natural conditions for the enjoyment of visitors along with the wellbeing of wildlife, and since 2002, natural sounds have received more emphasis.

Sound modeling was used in the decision regulating flights over Grand Canyon National Park and in the Yellowstone National Park winter travel plan.

“Modeling with maps is best suited for long-term planning because it allows us to look at changes in the amoeba-shaped sound field with changing sound levels and locations,” Fristrup said.

Such information is invaluable to groups demanding more development in and around public lands because with development comes noise.

A large body of research shows that wildlife avoid busy roads, snowmobile trails and development areas, such as oil and gas fields. But in the past decade, more studies have pinpointed noise as a specific stressor associated with those areas.

Continuous noise, even if it isn’t loud, affects many species, including those that use keen hearing to hunt in low-visibility conditions, like bats.

Noise is also hard on prey species, such as elk and mule deer, that can’t depend on their hearing to warn them, so they spend valuable grazing time looking for predators.

Reed’s model can identify if proposed development would be too close to species’ habitat, or it can be used to find locations that aren’t as detrimental.

“This is one of those rare areas where we identified a need and filled it,” Reed said. “It also seems really clear that there’s a growing interest in how sound affects everything.”

Laura Lundquist can be reached at 582-2638 or llundquist@dailychronicle.com. Follow her on Twitter at @llundquist.

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