Beavers Work Stream Restoration Magic In Birch Creek

The following story and photos are by Jay Wilde, an Idaho rancher and beaver-believer extraordinaire. The NRCS Working Lands for Wildlife team has led workshops on Birch Creek, where Wilde began reintroducing beavers a decade ago. We’ve learned a lot from him about restoring wet habitat, and appreciate his wisdom and stewardship!

The First Beavers In Birch Creek

I was riding out of Mill Hollow a while back. As I came out on to the road I couldn’t help but admire all of the work the beavers have done.  It’s been ten years since we released those first beavers. Their effect on Birch Creek has been nothing short of a miracle. 

Early on, I read countless papers and articles about beavers and what they can do for a watershed. I read with some skepticism, not sure if all of the things were true. But it fueled my interest to learn more and try to implement what the folks were talking about. I’m going to tell you some of the “cool” stuff that I’ve seen in the ten years since releasing those first beavers. 

We released those first five beavers (mom and dad, 2 yearlings and 1 kit) into a complex of beaver dam analogs (BDAs). We built the BDAs to give those animals a place where they would hopefully feel comfortable. We even built a makeshift lodge, then released them into it. I checked every day to see if they were going to stay put to establish some sort of beaver dam and complex. 

No activity, the first few days. So I’m thinking, “Here we go again”. Was this going to have the same results as my earlier attempts, when I’d brought in beavers without building any BDAs and they just disappeared?

About two weeks passed and I was getting really discouraged. I was wondering where they went or what had happened to them. While searching for some kind of sign they were still around, I happened to see what looked like an Aspen tree that was recently felled. Further investigation led me to the stream …. and there it was! A beaver dam! 

It was taking shape between a couple BDAs that we’d built. I guess they didn’t like where we released them, and they decided to move upstream a half-mile to set up shop in another complex of BDAs. They didn’t build on any of our BDAs. In fact, their dam eventually flooded a BDA that was about 40-50 feet upstream. 

That first dam was where the beavers spent their first winter. Their lodge was a rootwad from a subalpine fir tree that had been wind felled and was partially submerged in the pond. A food cache began to show up, so it looked like they were here for the long haul. 

I can’t tell you how relieved and excited I was to see that maybe we had been successful in bringing beavers back to Birch Creek. Were they here to work their magic? Was everything that I had read and learned about going to happen?

Beavers Survive The Winter

Winter soon set in and I left Birch Creek for Glenns Ferry. I left feeling comfortable with the fact that our beavers had decided to call Birch Creek home, but would they survive the winter? They had a food cache and a lodge. They had built their primary dam and a few smaller secondary dams. We were just going to have to wait until spring to see if they survived.

Our local irrigation ditch stockholders meeting is always the first Saturday in March. Going to this meeting always gives me an excuse to go back to the ranch to check on the house, barn and everything else that gets abandoned while I’m tending to things in Glenns Ferry. The peak of our calving is over by then, so it’s not a big deal if I leave for a few days. The main thing I wanted to check on was our beavers. Were they still there? Had they survived?

I dug out the snowbank in front of the garage and got my ATV out, heading up the canyon to where the beavers were in the fall before I left. What a relief it was when I could see trails and slides and all kinds of signs that the beavers were still there! They had survived.

An interesting thing happened as I was walking on top of the four-feet-deep snow. Usually the snow has began to thaw and settle by March, so it’s dense enough to walk on without sinking in. But as I neared the stream and beaver pond, one leg went into the snow clear to my hip. I could tell that it was hollow underneath the surface.

This was a bit of a mystery to me until all of the snow melted and I could clearly see that the beavers had hollowed out a snow cave and were using it as part of their lodge. There were all sorts of signs: peeled sticks, droppings and tracks in the mud indicated that they were using the snow cave during the winter. I’ve seen several places since that indicate they do occasionally use snow caves as temporary, makeshift lodges in winter. 

Beavers Go Gangbusters in 2016

Spring and summer came, and the beavers expanded their complex and built dams in the meadow where I wouldn’t let anyone build BDAs. That meadow is one of our monitoring sites and we had made a lot of progress restoration-wise, so I didn’t want to see it flooded. Turns out the beavers built dams and flooded it anyway. It’s all good, though. We’ve got several years of data and it’s interesting to see the changes in vegetation as a result of the beaver activity.

All through the summer of 2016 I watched the beavers’ activity with amazement. More dams were built and it appeared that the big pond at the bottom of the meadow was their new home. Their lodge took shape, and in the fall a food cache showed up. There was still some activity where they spent that first winter, but it was pretty obvious that home was at the bottom of the meadow.

In the fall of 2016 we hosted a workshop for NRCS folks. This whole idea of low-tech process based restoration (LTPBR) was starting to catch on. Jeremy Maestas brought a bunch of people from NRCS Working Lands for Wildlife to see what we had done on Birch Creek and to learn about building BDAs and LTPBR. They built several BDAs on the mainstem of Birch and a few in Mill Hollow.

Shortly after the workshop we released four more beavers into the BDAs in Mill Hollow. These beavers stayed right where we released them, and promptly added onto several of the post-less BDAs. Using post-less BDAs allowed us to build structures in locations that were too remote to haul in posts.

I still chuckle to myself about the argument that ensued about building post-less BDAs. It was Joe Wheaton‘s idea to try the idea, but Jeremy had brought in all these people to learn how to build BDAs with posts! Anyway, the beavers seemed to like the post-less ones quite well.

The beavers that were released in Mill Hollow were live-trapped in a different spot from the ones released in the fall of 2015. We thought we probably needed some genetic diversity so that offspring from the original families could find mates when they dispersed.

Beavers Stimulate Aspen Growth

Some folks don’t like the beavers taking down aspen trees. However, if you want to promote aspen regeneration, all you have to do is cut one down. Aspens are rhizomatous, so cutting one down stimulates a new tree to emerge from the root system.

When the beavers take down aspens, they actually stimulate new growth. It’s kinda what the aspen groves need to stay healthy.

Aspen seems to be what the beavers prefer when it comes to food and building materials. Evidently, the bark and cambium of the aspen satisfies their nutritional needs — or maybe it just tastes good! Willows are probably their next favorite to take down. They don’t seem to like the narrowleaf cottonwoods we have here.

One thing that always generates questions when folks are touring Birch Creek are the four-foot-high tree stumps around the beaver complexes. Well, it’s not that we have four-foot tall beavers! It’s because the snow is that deep when they cut the trees down in winter. Beavers don’t hibernate, and although they are fairly dormant they do venture out in search of food in winter.

Rotational Harvest Of Beavers

From what I’ve seen, a family of beavers will use a primary dam with its lodge, as well as the accompanying secondary dams, for 4-6 years before moving to a different location. They leave because either their primary dam fills with sediment and no longer gives them the protection they need, or because they exhaust the food supply at that location.

When beavers abandon a complex, those dams still hold water for some time. The sediment captured in those dams becomes exposed as water levels drop, and is highly fertile. The abandoned ponds create “mini-meadows” that are rich in forage for wildlife and livestock.

Eventually, the woody species along the banks will grow back. Then the beavers will return to their previously used complex and set up shop again. We’ve seen this happen in one area. The complex was active from 2016-2019, then in 2025 we once again saw beavers using the complex.

Beavers are kind of like rotational crop farmers. They harvest for a few years, then leave and let it regenerate. When the trees and willows are just right, they return again for another harvest.

Beaver Dams Boost Trout Numbers

Birch Creek is home to an isolated population of Bonneville cutthroat trout. DNA work shows this is a pure strain that has not been hybridized.

As a youngster, I was always able to catch these native cutthroats all up and down the creek. As flows diminished and the beavers disappeared, the fish nearly vanished. The fish that remained were very small, few and far between.

It turns out that the beavers were just what the cutthroats needed! Enhanced pond habitat and more dependable flows led to a huge increase in the number and the size of fish in Birch Creek.

I’m hearing reports that the fishing is pretty good in those beaver ponds. The Forest Service electrofished the creek in 2001 and 2012. We did it again in 2019. The graph above shows the results. Amazing! And it’s something I hadn’t even thought about.

This beaver reintroduction project has taken place on Caribou-Targhee National Forest land. Several U.S. Forest Service personnel have been involved, like Brad Higginsen, a hydrologist. He helped with the permitting process with Idaho Department of Water Resources and the Army Corps of Engineers. Two fish biologists–Lee Maybe (since retired) and Corey Lyman–realized that the culvert under the USFS road where Mill Hollow enters the mainstem of Birch Creek was creating a fish barrier and stopping the migration of cutthroat trout into the Mill Hollow.

Brad acquired a grant to replace the culvert with a bridge. Now the fish can access the Mill Hollow stream and all of the beaver pond habitat that has been created. We’ve also seen signs that the beavers are going under the bridge to move between Birch Creek and the Mill Hollow stream.

How High Can Beaver Dams Get?

While doing a workshop in Nevada, I saw a beaver dam that couldn’t have been more than 2 feet high. It backed water up for at least a quarter-mile. In flatter areas, the beavers can create a huge pond with not much of a dam.

The gradient of Birch Creek from the headwaters to the forest boundary averages 7%, however. That’s pretty steep. The beaver dams have to be quite high in order to create much of a pond.

The primary dams we see in Birch Creek are anywhere from 6 to 12 feet. I’ve been told it’s unusual to see a dam more than 4 feet high. That may be true on streams with a lesser gradient, but here we’re seeing dams built much higher.

That makes for a deep but short pond. It’s been fun to watch as they start in the stream channel with not much of a dam in the beginning. Then over time, they keep adding on to it and eventually it gets high enough and wide enough to create a pond to fit their needs.

All of our complexes have one large primary dam and several secondary dams. Why all the secondary dams?  My thoughts are two-fold. It’s likely that it adds security as the beavers travel up and down the stream. If they feel threatened by a predator, they’re not far from the safety of a pond. My other thought is that it makes moving wood up and down the stream easier. It’s easier to float a log than to drag it across dry ground.

Thinking Like A Beaver

When building BDAs I like to try to think like a beaver. Where would they be likely to put a dam? But I’ve pretty much given up trying to think like a beaver. Just about the time I think I have them figured out, they do something different!

Two different places where we built BDAs, the beavers decided to put in a dam of their own, flooding the BDA that we put in for them.

Probably the most important thing that beavers do is raise the water table with their dams and ponds. During high flows in the spring when the snow is melting, water spreads out of the stream to saturate the floodplain. Most undisturbed floodplain soils can hold 30% of their volume in water!

When streamflows drop back down in the summer and fall, the higher water behind the floodplains wet and keeps water in the channel.

So, while we see a lot of water being stored in the ponds, what we can’t see is the water being stored in the floodplain soils. That water helps to feed the stream through the dry season and helps it keep flowing year-round.

Restoring Year-Round Flows to Birch Creek

When I embarked on this journey to bring beavers back to Birch Creek, my goal was to restore perennial flows. Mission accomplished! We’ve had perennial flows in Birch Creek for the past 4 years (2022-2025).

Beavers do so much more than just affect the streamflow. Every time I venture up the canyon above the ranch, I see something new that the beavers have created. It boggles my mind to think of what this country looked like before the near extinction of these watery rodents!

It gives me a warm, fuzzy feeling to know that the return of perennial flows through the ranch benefits many more critters than just me. Fish, birds, deer, elk, moose, and so much flora in this watershed are all much better off now because of the beavers. 

I get a lot of the credit for bringing the beavers back to Birch Creek. But the fact is, I couldn’t have done it without the help of a lot of folks. I tried it on my own and was unsuccessful.

When I sent an email to Joe Wheaton a decade ago and told him what I was trying to do, it opened up a whole world of knowledge and experience. I had finally knocked on the right door. I’ll be eternally grateful to all of the folks who helped and encouraged me along the way.

I’m also grateful to have been a part of workshops from Nevada to Kansas to Utah to Alberta to tell my story. I hope that it has inspired folks to change their minds about beavers and welcome these helpful rodents back into their watersheds.

I’ve learned so much along the way. It’s been a great journey!