Click here to read about the National Park Service's Natural Sounds Program.

From their base in Fort Collins, Natural Sounds Program's acoustic biologists travel around the U.S., documenting everything from bear calls to the croaks of spotted frogs. These researchers collect recordings of the true sounds in a natural environment and use them to help shape sound policy in the country's national parks. This year, as the Grand Canyon faces the challenge of substantially restoring its natural quiet, the work of the Natural Sounds Program is especially important. Here, a collection of images and recordings from the biologists' fieldwork.

Black Bear - Yellowstone National Park

Steller's Jay - Bandelier National Monument

Ocean - Olympic National Park

Coyote - Rock Creek Park

Elk - Redwood National and State Parks

Northern Flicker - Presidio of San Francisco

Red Squirrel ¬- Wind Cave National Park

Ptarmigan - Yukon Charley Rivers National Preserve