This article was originally on Highland news.
The first grainy clip of film shows a black bear exploding out of the trail camera frame. In another, a mule deer stops chewing wildflowers, backs away, and takes off in the opposite direction. In a third, a moose does not move at all, but remains alert.
All three animals responded to sound bites from boomboxes in the woods, part of a study looking at the effect of the sound of outdoor recreationists on wildlife. The sounds included people talking, mountain bikers running down trails – even just silent footsteps. Each clip was less than 90 seconds long.
The new study, currently being conducted in Wyoming’s Bridger-Teton National Forest, adds to mounting evidence that the mere presence of human noise, no matter how loud or quiet, fast or slow, changes animal behavior.
Don’t start feeling guilty about going for a walk just yet, though. Researchers are also trying to understand the meaning of those reactions. For some species, walkers and cyclists may be an afterthought in a forest full of natural disturbances. For others, recreationists can have an impact similar to that of terrifying predators, which invade habitats where food can be found, resulting in lower birth rates and even more deaths.
“The whole point of the study is not to vilify recreationists,” said Mark Ditmer, a research ecologist at the U.S. Forest Service’s Rocky Mountain Research Station and one of the study’s co-leaders. “It’s to understand where and when we cause the most nuisance.”
The idea that we need to know and love the outdoors in order to protect it has been prevalent for over a century. Recreation built up a constituency that helped protect wild places. But even decades ago, there was evidence that the use of wilderness – whether formally designated or not – as a human playground caused much of the collateral damage. Paths crossed forests without rhyme or reason; used toilet paper hung from backwoods bushes. Groups like Leave No Trace began reminding people to take their trash, leave wild animals alone, and defecate responsibly.
Still, “non-consumptive recreation,” the weird term for enjoying the outdoors without hunting or fishing, is generally considered a net good. At best, outdoor recreation connects people to the land and sometimes inspires them to protect it — to write to legislators, attend land-use meetings, support advocacy groups, perhaps remind others to stay on trails. At worst, it seems harmless.
“The whole point of the study is not to defame recreationists.”
But recent studies show otherwise. There is one from Vail, Colorado, showing an increase in trail use by hikers and mountain bikers disturbed moose so much that the cows gave birth to fewer calves. Another from Grand Teton National Park showed that backcountry skiers frightened bighorn sheep in winter when food was scarce, with potentially deadly consequences. A 2016 review of 274 articles on how outdoor recreation affects wildlife revealed that 59% of interactions were negative.
But most of the research looked at the impact of random encounters with hikers, backcountry skiers and others. Few have wondered what exactly it is about humans that disturbs wildlife so much, whether it’s the way we look, the way we smell, or the sounds we make.
“Often wildlife hears us before they see us, which is why we can rarely perceive whether it’s a negative response,” said Kathy Zeller, a co-leader of the new study and a research biologist at the Aldo Leopold Wilderness Research Institute and Rocky Mountain. ResearchStation.
Ditmer and Zeller decided to capture cycling and walking people in the woods. Last summer, they brought boomboxes of those recordings into the woods and put them on game trails away from heavily traveled areas.
On and off for about four months, when a motion-sensing camera at one end of the trail detected an animal, a boombox about 20 feet away played human sound bites — nothing like a 90s dance party, just recordings of two walkers getting on it was chatting or walking quietly, or of large and small groups of mountain bikers. Two more cameras near the boomboxes and one on the other side of the trail recorded wildlife responses. They also played forest sounds and even blank numbers to make sure the animal wasn’t simply reacting to sudden noises or the almost imperceptible sound of a speaker going on and off.
“Often wildlife hears us before they see us, and so we can rarely tell if it’s a negative response.”
Judging by an initial analysis of data from last summer, large groups of mountain bikers were the most likely to run away from animals like mule deer and moose. Smaller groups of mountain bikers and hikers talking also provoked a reaction. The animals stopped and listened to humans walking, but didn’t flee as often.
Researchers are still figuring out how harmful those reactions are. Joe Holbrook, a professor at the University of Wyoming who was not involved in the study, suspects it depends on the species and time of year. He and his team have spent years studying the reactions of wolverines to backcountry skiers and snowmobiles. His most recent work shows that female wolverines do not stick around to feed on carcasses when backcountry recreationists are nearby. That suggests they’re losing access to good habitat, but he still doesn’t know if that means they’re also having fewer babies or dying more often.
And some wildlife is getting used to the presence of humans: the herds of elk that roam the streets of Mammoth, Montana, the mule deer that chews roses in towns to the west, the pronghorn that roam golf courses and through subdivisions. Ditmer and Zeller found that in areas of more recreation, some species were less likely to flee.
Not all wild animals adapt to humans, however, and Ditmer said that when planning trails and other projects, consideration should be given to the impact we have on them — whether we can see them or not.
Christine Peterson lives in Laramie, Wyoming, and has been involved in science, environment and outdoor recreation in Wyoming for over a decade. Her work has appeared in National Geographic, Outdoor Life and the Casper Star Stand, among other things. We welcome reader letters. E-mail Highland news at editor@hcn.org or send an letter to the editor. See our letters to editors.