If you think the Wyoming Game and Fish Department's beaver translocation work has been all about conserving the species, you are only half right. There was a time when there were beavers everywhere, said Emily Fairfax, an ecohydrologist, beaver researcher, and assistant professor of geography at the University of Minnesota.

"Prior to the fur trade and prior to colonization, there was anywhere from 100 million to 400 million beavers spread across North America. And to put that into perspective, this is like a beaver for every single kilometer of habitable stream. They were truly everywhere," she said during a Western States Alliance podcast.

However, the true value to the ecosystems they thrive in isn't really about the colonies of beavers. It's about how their dams slow and impound water, she said.

"If we had 100 to 400 million beavers, that means we probably had close to a billion beaver dams on the continent," she said. "If you imagine what happens when we remove a single dam or a weir or a small rock structure that we built as people, that's a process that takes a lot of permits. That's a process that takes a lot of monitoring. We know it causes a lot of changes to the waterway," she said. "Now imagine removing a billion of these all at once."

Ecosystems across the nation saw massive changes to water flow. The shapes of the rivers changed. An enormous amount of sediment and material and wood was all flushed off the landscape.

"It's truly hard to describe what this continent used to look like when beavers were more in control of the waterways," Fairfax said.

Dam overview

When we think about what beavers are doing on the landscape, it's a common misconception that they're just doing this at a small scale. But a typical beaver family has a territory of 1-2 kilometers of stream and they're building dams and controlling the water flow throughout that entire territory. They build a lot of dams.

"This means connecting upstream to downstream of those canals, not just out across the valley bottom, but more like an interconnected highway of water," Fairfax said. "If you're looking at a beaver pond in isolation, that's like looking at one singular street when you're trying to understand how a city functions, you really do need to take that higher level view to see the scope of what beavers are capable of doing."

By some calculations, including a study by Marshall Wolf, a postdoctoral research associate at the Columbia River Inter-Tribal Fish Commission, there might be as many as 30 dams per colony territory.

However, in the same way that looking at a single beaver pond may not give you the system-wide view, researchers are now understanding that terrestrial wildlife biologists studying beavers and wildlands fire mitigation and fuels experts should be working together instead of completely separate.

The fire service adopted the strategy of focusing on core landscapes, to really strategically invest federal and state resources to maximize wildfire risk reduction. But one thing that's missing in that initial strategy was recognition of aquatic tools, said Wolf, who studies beaver dam analogs (man-made beaver dams).

"That's one thing that we're working on, is as the Fire Service continues to update that wildfire crisis strategy and its associated outcome based performance metric, that maybe beaver dams [and] analogs are included in that reporting as sort of an additional tool," he said.

Wolf has studied how teams can build analogs that act like a beaver dam in areas devoid of beavers, to repair riparian habitat as well as providing natural fire breaks. The theory is fairly simple; if woodland material is wet, it's not going to be susceptible to fire.

Renaissance man

The Cody Region's Terrestrial Habitat Biologist Jerry Altermatt spends much of his time researching areas prime for beaver translocations and working to trap problem beavers and move them into areas where they can thrive, delivering a shot in the arm to the new habitat to repair itself. But it's not easy.

When Altermatt is selecting areas, there's two main characteristics for which he searches. The number one thing he is looking at; are beavers needed in that area?

Other questions he asks when considering a site: "What are our issues? What were the problems that we're trying to solve at putting beaver in there?" he said during the WSA podcast. "If there is pristine habitat, we may not see it as a high priority, and beavers are probably going to get there anyway, but we might put them in there. But the other thing we're looking at areas that need some kind of enhancement, some kind of improvement."

Altermatt has been translocating beavers for eight years now. Once he has identified areas in need of the industrious rodents, he looks at some of the physical attributes to know whether it's going to be feasible for beavers to stay put when he relocates a family; like the stream gradient.

He looks for streams that have less than a 6% gradient, and ideally wants that to be around 2% gradient.

"If you think about it, when a beaver builds a dam, the more level that stream is, the more water they're going to get per dam effort. So viewers are always looking for streams that are more level than they are steep," he said.

Then he looks at stream power, both on the low end and the high end of turbidity. Then of course comes the woody vegetation. Beavers need to have woody plants in order to build their dams and store up their food caches for the winter. There needs to be something that's edible for the food, of course, so if the area doesn't have those species, then it's not going to be suitable for beaver.

He also looks at floodplain width. If it's a fairly narrow flood plain, we're not going to be able to expand that riparian habitat much, he said. So he is looking for areas that have a larger flood plain.

Then he finally looks at where those beavers might end up. He makes sure to look upstream and downstream to make sure that they're not going to get in trouble, either with a road culvert or some kind of irrigation structure.

"I consider [the lack of woody plants] the biggest challenge in the whole broad scheme of things. We have a lot of streams in my region, and this is true of most of Wyoming that we know once had beavers, and they don't anymore ... because the woody vegetation component is missing," Altermatt said. "Cottonwoods, willows and aspen are no longer in the system for whatever reason, and in order to get those areas ready for a beaver transplant, we have to first get those woody plants back."

Holding facility

Altermatt, a Renaissance man of sorts, first designed and built a trailer for holding beavers as he attempted to trap the rest of the family.

If Altermatt translocates beavers as they catch them, they will leave the new area in search of their mates and family while the trapping process is ongoing. So the department needed a temporary, safe holding facility until all the beavers can be caught and translocated at the same time, preserving the family units. The species is socially monogamous, generally living in discrete colonies composed of a mated pair and their offspring.

So Altermatt designed and, with the help of Game and Fish employees, built a holding facility in 2023 at the Cody Region office. The new facility can safely house up to 32 beavers in four separate families, which gives Altermatt the ability to work faster and more efficiently.

For Game and Fish, translocating beavers is a “win/win,” Altermatt said during the grand opening of the facility. The state has previously built manmade dams, called beaver dam analogs, or BDAs. But they’re expensive and getting a project off the ground requires a long, time-consuming bureaucratic process. However, there’s a simple permit process to trap and translocate beavers to places that need the industrious builders.

Still, the process is difficult. Live-trapping an entire family of beavers can take as long as two weeks, Altermatt said.

Thanks to Altermatt’s design — which includes removable doors separating the four individual pods — the biologist can actually be a matchmaker, introducing single beavers from different families to become possible mates.

"The holding facility has enabled us to greatly increase our capacity for translocating beavers, owing to the fact that up to four families of beavers can be held at once," he said. "Last fall, we translocated 30 beavers, of which 23 were housed in the facility. This is double the numbers we averaged per year prior to the facility."

For about two weeks, the facility was running at full capacity with four families. The facility has worked very well, although Altermatt has made a few modifications to improve the function over his original design.  

There have been matchmaking experiments in other states, but the facility in Cody is the first in the state that can help beavers find a mate. It won’t always work, but Altermatt can step in if they can’t get along.

“There’s really not a whole lot of difference in behavior between males and females. Females can be just as aggressive as a male,” he said. “They both mark their territory, and they’ll both defend their territory.”

Successful matchmaking will help increase populations as well as genetic diversity. The more beavers on the landscape, the better backcountry habitats will be.

Although a lot of work goes into the process, there is still a possibility trappers could undo the laborious process. But Altermatt said no translocated beavers have been lethally trapped, to his knowledge. 

"Most of the sites that we have released beavers into are either closed to trapping or are somewhat remote and not ideal trapping sites," he said.

The process saves the state a ton of money by avoiding the need to build BDAs.

“The cost savings is huge,” Altermatt said. “It’s 1/20th of the bureaucracy of manmade beaver dams and, if you consider all the cost of trapping and moving beaver, I’d say it’s less than 1/10 of the cost of doing a BDA.”

The entire cost of building the new holding structure was about $60,000, with an additional $10,000 to have an engineer review the plans. (The engineering costs were covered by the WYldlife Fund, a nonprofit partner of the department, with matching funds by Wyoming Untrapped.) Over the life of the new holding facility, thousands of beavers are expected to pass through, all building dams and creating wetlands 24 hours a day — as well as their future generations, he said.

Landowners who are experiencing problems with nuisance beavers can help the process by providing live trapping opportunities for Game and Fish. On the other end, landowners who have suitable habitat that are in need of beaver restoration can help by providing release sites. 

The first step a landowner should take is to contact their local warden or the Game and Fish Cody Regional office. Wyoming law allows landowners to lethally take beavers that are causing damage, but the definition of damage is fairly specific. For instance, damage to trees is not covered under the definition. Of course, allowing beavers to be live trapped and translocated is a great alternative to lethal take. 

Game and Fish is usually looking for good trapping sites in early spring, late summer and early fall, and, though not obligated to by law, can alleviate a landowner from nuisance beaver problems. 

"It's truly a win-win scenario," Altermatt said during a Tuesday email exchange.