“Noise interferes with all of the syntax a mammal, reptile, amphibian, bird, or insect would articulate,” he says. “Human noise crosses all the communication lines, and covers all the frequencies.” Animals use sounds in many important ways, including to defend territory and attract mates.
Affects of Noise on Urban Birds
Increasingly, human noise is all but drowning out bird calls and songs in urban areas. Traffic noise occupies low frequencies in the sound spectrum, and studies show that urban birds are singing in increasingly higher frequencies, says Elizabeth Derryberry, a post-doctoral researcher at Louisiana State University’s Museum of Natural Sciences. Research suggests that the songs of any specific bird species falls within a relatively narrow acoustic frequency. Singing at slightly different frequencies may help the birds hone in on others of their species. City birds are essentially forced to compete for a smaller slice of the acoustic pie.
Birds in noisy environments are also forced to sing louder, reports the National Park Service, causing them to use more of their precious energy to attract a mate or warn of predators, just as a person uses more energy to shout than to talk normally. In addition, urban birds probably spend more time being disturbed by noises and, therefore, less time feeding, says Richard Heilbrun, Texas Parks and Wildlife urban wildlife biologist in San Antonio. That makes it more difficult for them to replace the energy used competing with the noise.
Noise Disturbs Nesting Birds
Noise is known to flush nesting birds off of their nests, which leaves eggs and chicks vulnerable to predators, and uses up more of the adults’ energy. Big Bend National Park occupies an extremely remote corner of Texas. Typically, it is a very quiet environment. However, the military conducts flying exercises in the area, and Raymond Skiles, chief of science at the park, reports that military aircraft were affecting nesting success of peregrines. Designating resource protection areas on aeronautical charts and essentially routing the aircraft out of airspace over the park solved the problem. More difficult to solve will be the problem of boats flushing nesting shore birds. The National Parks Conservation Association hopes a national boater education program it is developing will reduce this impact.
Affects of Noise on Other Wildlife
Birds aren’t the only animals affected. Because most cat species rely on hearing to hunt, Heilbrun says, their hunting success decreases as noise increases. “Mountain lions and ocelots will specifically avoid roads, and noise is one of the factors,” he says. Certain wildlife simply won’t use noisy areas, says Bryan Faehner, legislative representative for NPCA, so noise, in effect, limits the populations of these species by limiting their habitat.
Most frog species sing in chorus to prevent predators from singling out an individual. Airplane noise disrupts this synchronicity and makes it easy for predators to pick off a frog or two. “Frogs are diminishing everywhere,” including in Texas, Krause says, “and one reason is human noise.”
In 2001, a study measured stress enzymes in the feces of elk and wolves in Yellowstone National Park. “Whenever there were snowmobiles around,” Krause says, “elk and wolves showed incredible amounts of stress.” Stress can burn excess energy in animals, make them more vulnerable to illness, and affect reproductive success.
The National Park Service Organic Act mandates the preservation of natural resources, including natural acoustics, in national parks.
Affects of Noise on People
Noise in national parks and other natural areas doesn’t just affect wildlife. It can also degrade the experience for humans. Air tours of national parks pose a particular dilemma. A law passed in 2000 required the park service and the Federal Aviation Administration to work together on the issue. While many nature-lovers hoped this legislation would help protect the natural sounds of our parks – something a majority of park visitors cite as a primary reason they are there – a plan has yet to be developed. “We don’t oppose air tours altogether,” says Faehner. “But we want to make sure they take place in a manner that is appropriate for the park and that respects park resources.” In some instances, he would argue that air tours should not be allowed. “Helicopters hovering over Gettysburg, for example, would not be appropriate.”
Noise produces “incredible amounts of stress” in humans, just as it does animals, Krause says. Fortunately, solving this problem won’t require large sums of money, technological advances, or legislation. People can make a huge difference if they simply become aware of the problem, eliminate unnecessary noise, moderate the volume of noise where possible, and confine essential loud noise to times of day and seasons when it will cause less harm. DON’T honk if you love wildlife.
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