Noise in Nature

Human-generated sounds threaten to overwhelm wild creatures.

By Claire Sykes

October 2008

Mowers and leaf blowers, sirens and jets—we sure can make a racket. All that blaring and blasting invades our lives and assaults our auditory canals. Whether we’re aware of the noise or not, it can take its toll on us—and on other living creatures within earshot.

“For humans, noise causes stress. That’s when the brain has to spend energy filtering out unwanted sound so our ears can receive the information we’re trying to get,” says Bernie Krause, PhD, bioacoustician and founder of Wild Sanctuary (www.wildsanctuary.com) in Glen Ellen, California, and author of Wild Soundscapes: Discovering the Voice of the Natural World (Wilderness Press). This explains why you can’t help but wince when a motorcycle thunders by.
Little is known about precisely how wild creatures receive and process human noise in their natural habitats, although recent studies indicate that the effect can be profound, Krause says, adding that “if the acoustic fabric of their environment is interfered with, their communication is masked.” That means they can’t chirp about mating and migrating or grunt over foraging and fighting.

Scrambled Signals

In forests, tundras and other biomes (major ecological areas) undisturbed by human-generated noise—which Krause calls anthrophony—“all vocal creatures acoustically structure their aural signals in an interdependent relationship to one another [bio­phony]. They do so cooperatively or competitively, much like instruments in an orchestra, so that each one can be heard distinctly from another,” he says. “For example, in many healthy habitats, certain insects occupy a specific frequency—niches of the creature bandwidth—while birds, mammals and amphibians occupy others not yet taken and where there is no competition.” But repeatedly bombard them with the roar of dirt bikes and the rumble of ships, and these creatures may flee their homes or even perish.

Consider the snowmobiles that vroom through Yellowstone and other national parks. In “Snowmobile Activity and Glucocoricoid Stress Responses in Wild Wolves and Elk” (Conservation Biology 2002), Montana State University’s Scott Creel reported that the engines’ commotion jacked up the stress levels in these animals.

Then there’s the spadefoot toad in the Eastern Sierra Mountains of California. At Mono Lake, Krause has observed that their synchronized choruses (so predators can’t locate any one toad) are broken up by the high-level noise of military jets flying overhead, inviting great horned owls and coyotes into their midst. The toads don’t start singing again for 45 minutes, enough time for predators to find a tasty amphibian treat.

Some animals adapt to our ruckus. Krause says that killer whales in the Straight of Juan de Fuca, bordering the US and Canada, and Friday Harbor in Washington State, for instance, “have learned to change the pitch and timbre of their vocalizations, generating a series of harmonics to make them sound louder.” Other whales take a detour and adjust their migrational routes. But for many of their cousins around the world, underwater marine-engine noise interferes with their sleep or drowns out their ability to hear that swish of a school of fish, and the whales can go hungry. The overall effect is that human-produced sounds make natural habitats noisier places while muzzling the wildlife.

Be Still and Listen

Krause has listened to the consequences of human cacophony over the decades: He has recorded more than 3,500 hours of natural soundscapes from all over the world since 1968. Today, nearly a third of the ecosystems he has collected have aurally vanished.

“Entire wild biome voices are disappearing at a rate so rapidly, that within this century there may be none left to record of any type unaltered or intact without the presence of human noise,” Krause laments. “What are our children going to hear? The sounds of animals and insects are the sounds of the divine. And they’re screaming for our help. But we’re the ones who have to shut up.”

When we do we can open our ears says R. Murray Schafer, one of Canada’s pre-eminent composers and music educators (www.patria.org). In A Sound Education (Arcana Editions), he offers 100 exercises in listening to “help sensitize you to the sounds of the environment.” One asks readers to note everything they hear right at that moment, pointing out sounds nearest and farthest away. Another has them write all the sounds that have disappeared in our lifetimes, such as the metallic ring of a telephone. “You have to listen, first, so you can understand how beautiful some sounds are and how vulgar others are,” Schafer says. “Listening can change the way you think and act regarding the effect of sound on other people and living things.”

When you tune your ears to the sounds around you, you begin to hear things you never had before. You notice the mundane hum of your refrigerator, but you also marvel in the miracle of robins singing. And you become more aware of your own aural impact on the world. So use a manual push mower and ditch the car alarm. Then go to a park or the beach and be still among the sounds of our animal and insect friends. Let them have their say.

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