EDITOR’S NOTE: This article is part of a MoJo series that goes beyond bison, bears and wolves to spotlight Yellowstone’s often-overlooked wildlife.
As we shake off the sparse snow of this winter and welcome longer days, another mammal also emerges, eager for the restoration of light. This large, semiaquatic rodent is the North American beaver.
Under waterways obscured by ice and in the dim light of their lodges, beavers can adjust their circadian rhythms up to 28-hour days in winter, which allows for more rest. It’s no wonder then that when the ice thaws, they come out ready to live up to their nickname and get busy.
Beavers have long been known for their industrious behavior — it can get them in trouble if misplaced in front of a ranchland culvert or on the trunk of a beloved fruit tree — but lately, this species is having a renaissance, earning praise for its skill in ecosystem engineering.
Like some humans, beavers prefer lodges — big ones. Torrey Ritter, a non-game wildlife biologist at Montana Fish, Wildlife and Parks, says their lodges can be as big as trucks. To build these freestanding homes, which they use as shelter from predators and also a place to rest, overwinter and socialize with their families called colonies, they need a pond. And if they don’t have one, they make one. Driven by an intense instinctual drive to create quiet, still water, they get to work building elaborate, watertight dams in flowing freshwater streams and rivers.
Their dams are made from nearby trees and shrubs, which they gnaw down with strong jaws and long teeth. Those teeth are sharp and orange and, like all rodents, grow continuously throughout their life. Because of this, beavers chew on wood daily to keep their teeth from getting too long. These mostly nocturnal animals work overnight to erect their dams that are then cemented in place and made leak-proof with the addition of mud, rocks and grasses.
Aside from humans, beavers are among the few animals that shape their environments. And as researchers, biologists and the public have learned more about the role they play in the face of a rapidly changing climate, we’re fortunate they’re up to far more good than harm.
One of the devastating effects of climate change is the dwindling of wetlands (the United States has lost over 50 percent of its original wetlands since the 1780s, according to a U.S. Fish and Wildlife Service Report), and the presence of beaver dams is instrumental to these ecosystems. The dams slow moving water and create habitat for other flora and fauna to thrive, including dragonflies, all types of amphibians, ducks, bats, and aspen, to name a few.
In the Mountain West this year, after one of the worst winter snowpacks on record, increased wetlands will prove crucial to creating landscapes that are more drought- and fire-tolerant. The vegetation that thrives in a beaver pond acts as a firebreak, and the pools allow water to seep into the soil more slowly.
“It’s all about the water,” says Amy Anderson, a terrestrial habitat biologist at the Wyoming Game and Fish Department. “And I think that’s going to be highlighted after a year like this. The only places we might have water are the places beavers are holding it back. And all of that water staying later into the summer is going to be good for everybody.”
That’s their role and what they’re so good at, Ritter continued, explaining that beavers make water work to get downhill. The slow-moving water forms a wetland corridor, full of elements that wouldn’t be there if it weren’t for beavers: back waters, side channels, oxbow bends.
North American beavers live across the United States and Canada (it also has a smaller Eurasian cousin), and while they were nearly brought to extinction by the fur-trapping culture of the late 19th and early 20th centuries, nearly 15 million beavers live on the continent today. While they’ve made a remarkable recovery, their current populations are not as robust as they were historically.
“It’s all about the water. And I think that’s going to be highlighted after a year like this. The only places we might have water are the places beavers are holding it back.”
Amy Anderson, terrestrial habitat biologist, Wyoming Game and Fish Department
What has also rebounded in recent years is their reputation. Wyoming, Idaho and Montana each have programs in place to help landowners and beavers become better neighbors to one another — Wyoming and Idaho have transplant programs and Montana is in the process of considering one. As of 2025, Montana also has a Beaver Conflict Resolution Program that provides landowners with cost-effective and nonlethal solutions, such as site assessments and device design. These methods aim to mitigate conflicts and build greater tolerance for beavers as well as an awareness of the benefits of their presence on the landscape.
“They’re important enough that we’ve begun mimicking them too,” Anderson said, pointing to beaver dam analogs, human-built structures that imitate the work beavers do in waterways where they’re needed. “But no one is as good at it as they are,” she said. “So keeping them will in turn keep water in these dry arid places like Wyoming, and that’s important.”
Important, you could say, and dam impressive.
