How Yellowstone’s animals survive a catastrophic flood

Yellowstone National Park turned 150 in March. In all of those years, it’s possibly never seen a flood as bad as the one this week. Record-breaking rainfall, along with warm weather that melted snow, turned the park’s rivers and streams into punishing forces that tore apart homes, roads, and bridges.

Park officials ultimately evacuated more than 10,000 visitors on Tuesday and the Montana National Guard rescued dozens of people from campsites and nearby towns, according to the Associated Press. There have been no reported deaths or extreme injuries so far, though homes were destroyed, and the floods could leave a scar on the region’s tourism-dependent economy. The northern portion of the park experienced the brunt of the damage and it could remain closed for months.

National Park Service

National Park Service

Catastrophes like this that harm humans and their livelihoods often impact wildlife as well, such as forest fires that destroy koala and kangaroo habitat and extreme heat that bakes marine life.

But this doesn’t seem to be the case here. According to wildlife officials, most of Yellowstone’s animals, from its iconic wolves to the elks they eat, are likely doing just fine — though there are a few exceptions.

Bears and wolves don’t mind floods. Neither do their prey.

Few animals in the US are more iconic than Yellowstone’s gray wolves, which trace their history back to a famous reintroduction campaign in the 1990s, when wildlife officials brought 31 wolves to the park.

Yellowstone’s 100 or so wolves can likely tolerate major flooding, as can the park’s other top mammalian predators, including grizzly bears, according to Douglas Smith, a senior wildlife biologist with the National Park Service, who works in Yellowstone. These animals don’t tend to den or travel near rivers, and their offspring are likely at least a few months old, making them less vulnerable, he said. (One visitor spotted a grizzly and two cubs in May. They’re very cute.)

Jacob W. Frank/National Park Service

Some of the animals that wolves and bears eat, like elk, moose, and deer, are also probably doing fine, Smith said. They could even benefit from the flood because the deluge of water gives the plants they eat a boost.

Meanwhile, massive herds of bison have simply taken to the roads to avoid the rising waters, as one TikToker documented.

Water birds are at risk, but they, too, are designed for this

Birds of prey like ospreys and eagles are incredible hunters — they can spot fish in the water from hundreds of feet away, and then dive bomb them (which looks pretty metal).

But that only works if the water is clear, and right now it’s not. Floods wash loads of sediment into rivers, making them murky. “The ospreys can’t see the fish,” Smith said. “Ospreys may be severely impacted as they depend almost entirely on fish.”

Jared C. Tilton/Getty Images

Birds that nest near the water, such as trumpeter swans and loons, may also face challenges as the water encroaches on their newly laid eggs, Smith said. “It could be complete reproductive failure,” he said, meaning that their eggs may not hatch. As soon as next week, wildlife officials will fly a plane over the park to check the status of the nests, he said.

But waterbirds also have strategies to withstand floods, as you might imagine. In one of the park’s lakes, wildlife crews saw that water is starting to breach the nest of a swan. “What she [the swan] is doing today is adding nest material to build the nest up to keep the eggs dry,” Smith said. “It’s going to be a race against the water.”

Jacob W. Frank/National Park Service

While it’s not ideal, losing eggs one year is not a major problem for most water birds in the park, he said. “Their whole ecology is to ride out bad years, where you get nothing,” Smith said of some of the park’s avian species. They often live for a few decades — loons, for example, can live past 30 — giving them plenty of opportunities to produce offspring in a year with better conditions.

A drop in visitors will likely help wildlife

Last year, Yellowstone had its busiest June on record, with nearly 1 million visitors driving and hiking through the park. That traffic is essential to the local economy, bringing in revenue and supporting thousands of jobs in the park and its neighboring towns.

The recent floods put this economic machine at risk, as the park may lose visitors this summer. But while that’s a problem for people, it may actually be a boon for wildlife, said Mark Boyce, a professor of ecology at the University of Alberta.

“The benefit is that there will be fewer people disturbing wildlife,” he said by email. “Traffic disturbs the animals, pushing them farther from roads later in the day.” (He’s actually done research that backs this up.)

It’s not roads themselves that tend to disrupt wildlife, he added, but people and traffic. And those disruptions can be costly for some animals, his research suggests, by making them use up energy to avoid people, that might otherwise go toward things like reproduction.

Climate change could push animals past their limits

Animals in Yellowstone, like in many places, have evolved to withstand dramatic changes in the environment — they’re used to flooding in the spring. “Although the runoff this year is extraordinary and record-breaking, mountains are known for big runoffs every spring,” Smith said. Bears, wolves, and other animals, he added, “are used to having uncrossable streams and rivers.”

What is concerning, however, is that these extreme events seem to be happening more often, likely due to climate change. Since 1950, spring rainfall has increased by as much as 23 percent in April and May (though it’s down in June), according to a big report published last year. The park is also getting warmer, the report found.

And this could have consequences for wildlife (as well as for people). In the past, any 10-year period would have a few good years, a few average years, and a few bad years for wildlife, Smith said. And now? “We think the quotient of bad years is increasing because of climate change,” he said.

So, while wildlife is likely to remain resilient in this disaster, we should also recognize that resiliency has its limits. The big problem for Yellowstone’s animals isn’t one bad flood. It’s that there could be many more extreme weather events in the years to come.

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