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Wildlife more sensitive to humans than thought

ELI FRANCOVICH Statesman from Idaho

We have a people problem.

That was the message Laura Prugh received several years ago from the US Park Service in Glacier Bay, Alaska. To Prugh, who studies human-animal interactions in the relatively busy state of Washington, the claim seemed a bit exaggerated.

After all, only 40,000 people visit the 3.2 million-acre park each year — absurdly low numbers for anyone accustomed to recreation in the Washington or Oregon Cascades, for example.

In fact, Glacier Bay is only accessible by boat or plane, and 94% of visitors arrive via cruise ship. But park service workers were reporting more and they wanted to know how — or if — that trend was affecting native wildlife. So visited Prugh, an associate professor at the University of Washington School of Environmental and Forest Sciences.

“I was just shocked at how few people were there,” she said. “And I thought, ‘Wow, these people really have lost track of what a lot of visitors are.'”

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Still, she agreed to conduct the research. Over the course of two summers, she collected footage from 40 motion-activated cameras in 10 locations, targeting wolves, black bears, brown bears and moose. She fully expected to find little to no “difference in animal activity between the high-use and low-use sites.”

In a study published this month, Prugh and her coauthors found that when humans were present, the cameras detected fewer than five animals per week in all four species studied. In most cases, this probably meant that animals avoided areas where humans were present. Second, wildlife detections in backcountry areas fell to zero each week once outdoor recreation levels reached the equivalent of about 40 visitors per week. The researchers note that in some places where animals are more used to humans, the response to human presence will be less.

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While it’s just one study, in one place, the findings have implications for recreation management.

“Our research indicates that if people want to recreate and minimize their impact on wildlife, it would actually be better to go hiking on busier trails, because those locations disturb nature anyway,” she said. “I think there’s a trade-off with human experience and the impact on wildlife, unfortunately.”

A field in development

The question of how, or even if, human outdoor recreation of the non-hunting variety affects wildlife is “kind of an emerging field,” Prugh said. Despite its relative youth, numerous recreation ecological studies have shown that animals change their behavior in response to human presence.

Some mammals have become nocturnal, abandoning their normal daytime routines in the hope of avoiding human presence. In Montana, wolverines and bighorn sheep avoid areas where backcountry skiers shred. According to another study, wild reindeer flee farther and longer for backcountry skiers than for snowmobiles.

That’s all well documented; what hadn’t been looked at, however, was the minimum disturbance threshold or, more simply, how many people it would take to send a grizzly pack, said Joel Berger, a professor at Colorado State University and the author of “The Better to Bring You to eat: Fear in the animal world.”

The UW study is beginning to answer that question, he said. Berger was not part of Prugh’s study and has not met her, although he said he admired her research.

“The Prugh study provides the first quantitative evidence, in my opinion, of animal species’ responses when exposed to humans in these low-density situations,” he said.

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He said it also showed variation in species’ response to human activity, noting that Prugh’s study found moose were more active when humans were around, indicating that the large ungulates used human presence as a shield against more wary animals, such as wolves. That’s known as the human-shield hypothesis, a term coined by Berger.

“The question is, what do animals need to learn?” he said. “To be able to apply this anti-predator strategy against harassment.”

In addition to these questions, the study also raises a conundrum for recreation planners and outdoor enthusiasts, both in remote and more urban settings.

Consequences for recreation

The balance between recreation and wildlife is something Paul Knowles, Spokane County’s park planner, thinks about often.

“As a land manager, in a sense, you sacrifice some areas so that others can be devoted primarily to wildlife habitats,” he said.

When county planners design and build trails, they try to include “natural disturbance buffers.” These buffers are built using the best available science about how much space species of humans need. However, in an urbanized environment like Spokane County, it’s not always possible to take up that space.

Anecdotally, at least, Knowles said he’s heard “over and over again” that once a property is acquired by the county and developed for recreation, wildlife sightings plummet.

“We are acquiring these protected areas for multiple purposes and multiple benefits, including recreation,” he said. “So we have to find a way to balance that out. It is heavy.”

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