Wildlife in national parks: How do they act when people are gone?

In the summer, wildlife watchers head to U.S. national parks hoping to catch a glimpse of a moose, a bear, or maybe even a wolf. But even with so much wildlife around, those moments are rare. A major study has just helped explain why.

The COVID-19 shutdowns in 2020 presented a unique opportunity to watch what animals do when people disappear. A multinational team of scientists from 13 universities, including the University of Nebraska–Lincoln, took advantage of this moment.

The researchers tracked how large mammals behaved in the absence of people across 14 national parks and protected areas in the United States.

When people disappeared

Researchers from the University of Nebraska–Lincoln were among more than 60 scientists who collaborated on this massive project. They worked with partners like the National Park Service and several state agencies.

Using GPS collars, the team tracked 229 animals, including predators like wolves, mountain lions, grizzly bears, black bears, and foxes, as well as herbivores like moose, elk, mule deer, mountain goats, and bighorn sheep.

The experts compared animal movements during the pandemic shutdowns in 2020 to the same period in 2019, when parks were bustling with tourists.

A natural wildlife experiment in parks

The parks studied included Yellowstone, Yosemite, the Grand Canyon, Zion, Glacier, and others – some of the most iconic and heavily visited in the country.

“COVID provided ecologists with a valuable natural experiment,” said John Benson, one of the study’s researchers.

“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.”

Wildlife reaction in different parks

The main finding? Human activity leaves a mark – even when people aren’t there. While animals generally avoid roads, parking lots, trails, and campgrounds, their reactions aren’t all the same.

“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 of the University of British Columbia, lead author of the study.

The team noticed that some species and individuals took advantage of the quiet, exploring areas they usually avoided. Others stuck to old habits, avoiding human infrastructure even when it was empty.

“There are so many factors that influence animal behavior: local environmental context, species, sex, age, seasons,” Benson said.

“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.”

Wild animals that benefit from humans

Some species are more cautious. Others seem to adapt. “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 explained.

“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.”

Most animals didn’t change their behavior

In parks with more development, wildlife was more likely to explore previously avoided areas during closures. But the shift wasn’t as dramatic as headlines in 2020 might have suggested.

“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.

Still, most animals stuck to their usual avoidance behavior – even when parks were closed.

“While some individuals and populations showed a strong response to the absence of people during park shutdowns, most did not,” Gaynor noted.

“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.”

Why didn’t more animals take advantage of the quiet? The researchers have a few ideas. First, the closures were short – just 58 days on average. That may not have been long enough for animals to sense a real change.

Furthermore, animals that avoid people might already have been pushed to quieter areas long ago. Meanwhile, those used to humans may have barely noticed the difference.

Parks shape people and wildlife

Human presence changes the game for wildlife. It affects how animals find food, avoid predators, and interact with each other. That has ripple effects on entire ecosystems.

“The national parks have a dual mandate to preserve natural and cultural resources, while also providing enjoyment of the parks to people,” said Benson. “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.”

Balancing recreation and conservation

Before the pandemic, U.S. national parks saw 327 million visits in 2019. That number rose even higher in 2024 to nearly 332 million.

“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.”

The full study was published in the journal Proceedings of the Royal Society B.

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