Many summer visitors to America's national parks hope for a glimpse of a moose or a bighorn sheep — or perhaps to spot a wolf or a bear.
A newly published study by a multinational group of wildlife scientists took advantage of the opportunity offered by the 2020 COVID-19 shutdowns to better understand why such glimpses can be so elusive.
Using GPS collar data, researchers tracked 229 animals from 14 U.S. national parks and protected areas. They compared the animals' movements while the parks were closed to visitors during the 2020 COVID-19 pandemic to movements during a similar time frame in 2019.
Some of America's most beloved national parks were included in the study, such as Grand Canyon National Park in Arizona, Yellowstone National Park in Wyoming, Yosemite National Park in California, Zion National Park in Utah and Glacier National Park in Montana. The movements of five predator species — wolves, mountain lions, grizzly bears, black bears and foxes — and five ungulate species — moose, mule deer, elk, mountain goats and bighorn sheep — were tracked.
John Benson of the University of Nebraska–Lincoln was part of the team of more than 60 scientists representing 13 universities and nearly 40 other entities, including the National Park Service and state agencies. Benson, an associate professor in the School of Natural Resources, helped conceptualize the study, which sought to tease out whether animals shy away from human infrastructure like campgrounds, parking lots, roads and trails even in the absence of human beings.
"COVID provided ecologists with a valuable natural experiment," he said. "We know that animals can respond strongly to humans, but it is often not clear whether they respond to the 'human footprint' of roads, trails and development, or to the humans themselves. Our study allowed us to separate the foot from the footprint to an extent."
Wide range of responses
The study showed that the presence of humans and human infrastructure has lasting effects on the large animals that call U.S. national parks home. These findings contribute to a better understanding of how human activity influences animal behavior within protected areas — an important step toward understanding how humans might influence their survival and reproduction.
"Wildlife all around the world fear people and avoid areas of high human activity, but it was surprising to see that this holds true even in more remote protected areas," said Kaitlyn Gaynor, a zoologist at the University of British Columbia and lead author of the paper published July 30 in the Proceedings of the Royal Society B .
While overall animals tended to avoid infrastructure such as roads, trails, parking lots, buildings and campgrounds, closer analysis showed responses varied across populations, species and individual animals.
"There are so many factors that influence animal behavior: local environmental context, species, sex, age, seasons," Benson explained. "In a large-scale analysis with many species across so many parks, it was important to separate variation in behavior resulting from all these other sources, from changes in behavior due to reduced human activity during COVID."
"Some species are just more wary of people than others, like bighorn sheep and mountain lions, while others have learned to associate humans with some benefit," Gaynor said. "The mule deer and elk in Zion National Park prefer being closer to developed areas and around humans. That could be because their predators might be avoiding people, so if deer and elk can learn to live with us, they can reduce the risk of becoming prey."
Avoidance even during lockdown
The researchers found animals in more developed areas switched from avoiding human infrastructure when the park was open in 2019 to using it more when the park was closed in 2020. Without any people around, animals were apparently more willing to explore the developed areas of the park.
"We heard from managers in Yosemite National Park that when people came back, the black bears stayed, which caused a lot of problems because the bears got used to the abundant food in Yosemite Valley and didn't want to give it up," Gaynor said.
But in most other parks, avoidance of human infrastructure persisted even during the lockdowns.
"While some individuals and populations showed a strong response to the absence of people during park shutdowns, most did not," Gaynor said. "Because a lot of headlines in 2020 implied that animals were taking back our national parks and were on the streets everywhere, we expected to see a bigger effect. But it takes just a few individuals to start changing their behavior to create the perception of a larger impact."
The researchers speculate that due to the relatively short duration of park closures — an average of 58 days — many animals may not have had enough time to perceive and respond to the change in human activity, particularly those with low exposure to human development in their home ranges. Additionally, risk-averse individual animals and species may have already been displaced prior to the pandemic, while those animals with a high exposure to humans were already habituated.
A fox rests in the snow near Fort Collins, Colorado.
Balancing recreation and conservation
Human presence influences both the resources available to animals and the risk of using those spaces, with differing effects on animal species. The responses of animals may shape which species eat and compete with each other, changing ecological dynamics, the researchers say. These responses may also affect the ability of animals to persist alongside people in protected areas.
"The national parks have a dual mandate to preserve natural and cultural resources, while also providing enjoyment of the parks to people," Benson said. "This made national parks really interesting places to study animal behavior during COVID closures. While we often think of national parks as some of the last truly wild places on earth, some also receive intense visitation by humans."
U.S. national parks hosted more than 327 million visits in 2019, prior to the COVID closure. The number rose to a record 331.9 million visits in 2024.
"Yellowstone National Park, Yosemite National Park and the Grand Canyon are international destinations that are crowded at peak times of year, but the crowds are concentrated near the roads and visitor centers and parking lots," Gaynor said. "The study provides evidence that conservation is compatible with recreation at low levels but that we do need to keep some areas exclusively for wildlife."
