Why does Tim Mullet plan to collect moose poop for a two–year study of noise levels on Kenai National Wildlife Refuge in Alaska? Because bagging moose pellets is safer and easier than taking blood samples from wild horned animals weighing half a ton and up.

Mullet, a biological technician at Kenai Refuge and a PhD candidate at the University of Alaska Fairbanks, will test the moose poop for levels of glucocorticoids—hormones that are indicators of animal stress. Chronic high levels of these hormones can lower wildlife densities and displace animals from preferred habitat. Mullet hopes to find out whether exposure to human–made noise causes such stress.

One source of human-made noise is snowmobiles. Snowmobile use is permitted on the refuge under the provisions of the Alaska National Interest Lands Conservation Act (ANILCA), especially for hunting and fishing, even in wilderness areas.

Noise from human activity is penetrating deeper into Kenai Refuge’s 1.3 million acres of wilderness, and growing recreational use of snowmobiles has sparked some visitor complaints, says John Morton, supervisory wildlife biologist at the refuge for the past decade. The area also absorbs noise from Sterling Highway, which passes through the refuge on the Kenai Peninsula about three hours south of Anchorage.

“At this point, I’ve got an idea that 30 to 40 percent of Kenai’s wilderness could be affected by human–made noise,” says Mullet. His study will map a “soundscape” of the refuge, based on sound-level readings and recordings and predictive modeling. Sound is measured in decibels (dB), with conversation usually measuring about 60 dB and a jet take–off about 120 dB, loud enough to cause permanent hearing loss.

Readings previously taken on Kenai Refuge include 95 dB for low–flying aircraft and 120 dB on or near Sterling Highway.

The study—conducted with the Ecological Wildlife Habitat Data Analysis for the Land and Seascape, and overseen by Mullet’s academic advisor, Falk Huettmann—goes beyond simple decibels (loudness), though. It is a foray into the emergent field of soundscape ecology, which examines the interplay of anthrophony (human–induced sounds) and biophony (natural sounds).

“It’s Definitely Cutting Edge”

Loudness is “a piece of this study,” says Morton, “but another piece is the origin of sound—whether it’s human or nature—and developing a ratio between the two. It’s definitely cutting edge.”

Understanding the relationship between anthrophony and biophony is important to the refuge and wildlife conservation in general, Morton says, because “human–generated noise can drown out natural noises—and that can be a huge deal, to the point where animals can’t actually hear themselves.”

The study will focus on “recognizing how snowmobiles specifically affect the winter soundscape and how winter soundscapes differ from summer soundscapes,” Mullet says. In summer in wilderness, airplanes, singing birds, road traffic and raging rivers can be heard, he says. Winter, he says, generally is quieter because road traffic is lighter, wildlife is hibernating and snow has insulating properties. Motorized vehicles, aside from snowmobiles, are also absent from wilderness.

Sound samplings are beginning in earnest in this year. Conclusions from the study are not expected until 2014, in part because the work involves unwieldy data sets and “a heavy–duty analytical piece at the end,” Morton says.

“As far as I know, nobody has attempted to model sound in the landscape,” says Mullet. “We could encounter some big surprises there.”

Susan Morse is a writer–editor in the Refuge System Branch of Communications.