Beaver! A surprisingly loaded word. The largest rodent in North America. Oregon’s state animal. The American Beaver is touted for its remarkable ability to engineer waterways. While simultaneously villainized as a nuisance species. Trapped for its fur well into the 19th century, this activity still occurs today, though not to the levels seen during the fur trade.
There are a lot of strong opinions about beaver. They are both beloved and hated. Removed and reintroduced. Marveled at and frowned upon. Yet, for all the attention they get, there is a lot we still don’t know about them.
This is why, after a long day of teaching high schoolers, I met up with Vanessa Petro, who has been studying the American Beaver for over 10 years, to walk and talk about these surprisingly enigmatic, charismatic creatures.
The Hike
- Trailhead: Alsea Falls Trailhead
- Distance: 2.4 miles (w/shorter and longer options available)
- Elevation Gain: 300 ft
- Details: Ample parking and pit toilet available at trailhead. Drive to trailhead is on well-maintained gravel roads. $2 for parking or use National Forest or other Recreation pass.
The Drive
Vanessa and I drove out to the trailhead together. As we rode along, we chatted about various aspects of our lives—from childhood to career to motherhood.
Vanessa spent her childhood in Pennsylvania, surrounded by nature and the outdoors. “I grew up going out the backdoor and disappearing into the woods,” said Vanessa, much to the chagrin of her parents.
But it wasn’t until she encountered a magazine article featuring Dr. Gary Alt, a renowned black bear biologist, that she initially got hooked on wildlife. Vanessa saw what Dr. Gary Alt was doing, and as she put it, she “wanted to do something like that.”
Vanessa’s passion for wildlife and the outdoors continued into high school. She was active in hunting during her teen years. And she enjoyed classes in the biological sciences. In particular, Vanessa mentioned an ecology teacher that inspired her and also invited her to compete in a state-wide natural resources competition called Envirothon.
College and Career
Vanessa’s was on a path. After high school, she attended Sterling College, “the smallest accredited college in the United States.” The college only offers environmental study-based majors. Vanessa studied conservation ecology.
“I lucked out while I was there,” Vanessa explained, “There is a large emphasis on hands-on experience. “By the time she graduated from Sterling, Vanessa had already completed several seasons of summer and winter field work, including an internship with Sequoia National Forest working on a forest carnivore monitoring project.
After graduation she bounced around the U.S., living in 11 different states, as she continued to find seasonal wildlife work where she could. “I have no regrets,” Vanessa smiled, “except for maybe a few men.”
Eventually, Vanessa settled at Oregon State University to conduct graduate research. And once graduated, continued her research work at OSU, which is where she is today.
Now, married with one child and another on the way, Vanessa spoke adamantly about the challenge of balancing a career with family. “In natural resources, you can’t really get married and have children at the start of your career,” she said pointedly. “I had to wait.” Even today, with a supportive boss and colleagues, Vanessa spoke of the difficulty. “There is a high attrition rate for women in STEM fields,” she noted.
Why beaver?
Before long we pulled into the parking lot for Alsea Falls and our trailhead. And after a quick restroom break, Vanessa and I headed down the muddy path to Alsea Falls.
Vanessa has been studying Beaver in the Alsea River Watershed for over 10 years. So, as we began our descent, I needed to ask— “Why beaver?”
“For me, I am definitely split between terrestrial and aquatic systems,” Vanessa responded. “And they are in between.” Beaver are semiaquatic—spending part of their time and on land and part of their time in water—taking advantage of resources in both environments.
In addition, many people care about beaver. “There is a lot of conservation interest in beaver in our area,” Vanessa went on. “And there is a lot we don’t know about them.”
Unknowable
Despite their dominating presence in the Pacific Northwest’s history, we don’t even know the most basic information about beaver in this region. “No one can tell you long they live or how many there are in our state,” explained Vanessa. Their ecology is a mystery.
So, what is happening? Most studies center around using beaver in restoration and/or the relocation of beaver. Questions are very specific and very limiting. For example, “we don’t know the average home range sizes of beaver throughout our state,” but we have movement data for relocated beavers. Yet, beavers that are relocated do not behave the same as naturalized beavers, so it would be like comparing apples to oranges. Thus, there is a gap in knowledge.
Alsea Falls
Vanessa and I continued until we reached the first Alsea falls viewpoint. We stepped out onto the bedrock ledge to get a view of Alsea Falls and snap a few pictures. The ground was slick, but that didn’t stop Vanessa from clambering up closer to the falls for a photo when I asked.
We continued down to the lower viewpoint for another view of the falls from a wider angle. I noticed how the autumn leaves opposite the river were striking against the dark greens and greys of the forest. We looked out at the rushing water.
Dammed if you do, dammed if you don’t
“Do you know what is cool about where we are standing?” Vanessa started, looking upstream, just above the waterfall. “This waterfall is a known barrier for salmonid fish.” But that isn’t the interesting part. Vanessa went on to explain that not too far upstream there is a two-mile stretch of river that beaver have colonized, building dams and creating the perfect habitat for fish.
Beaver are considered ecosystem engineers—they create habitat other species, like salmon, rely on. Birds, amphibians, and invertebrates all take advantage of the engineered wetlands, pools, and other habitats built by beaver. The list of beneficiaries is long.
The site upstream of Alsea Falls is so ideal for salmon that at one point multiple stakeholders wanted to build a fish ladder to provide the fish access to it. The idea eventually lost steam, but just the fact it was considered, says a bit about the quality of fish habitat beaver have the potential to provide.
However, it is important to note that not all beavers make dams. They often don’t need to. And without dam building the ecological benefit of beaver is non-existent.
If water around their dens and foraging areas is deep enough to protect them from predators, a beaver won’t build a dam. Beaver innately rely on these cues to know when to build. Below Alsea Falls dam making isn’t as frequent and “habitat is patchy,” said Vanessa. The cues aren’t there.
The two-mile stretch of beaver dam habitat above Alsea Falls that everyone desires, well, “that doesn’t occur frequently on the landscape,” said Vanessa.
“Salmonid habitat ends right here,” stated Vanessa, matter-of-factly. But beaver habitat, well that is another story. We followed the trail back upstream with beaver in mind.
Beaver Forage
Back at the top of the trail, we took a sharp left onto a bridge that crosses the Alsea River. I looked down at the flowing reflective waters. Vanessa looked out toward the greenery lining its edges with an eye out for beaver sign.
Beaver are herbivores—they eat plants. More specifically, they snip off smaller diameter branches of trees and shrubs, eat the leafy greens and outer layer of bark where the cambium is.
They are picky eaters though. “They will cut salmonberry, red alder branches, willow, and vine maples… but they won’t touch Pacific ninebark,” said Vanessa. “They will eat lady fern,” but avoid stink currant.
Beaver generally stay close to the water and often sit along its edge while consuming the forage they collected. “They will forage on average about 30 meters (~100 feet) from the waterline,” stated Vanessa, “but will go further out if they have to.”
“They look for the best of the best,” Vanessa told me later during our hike. Though the Alsea Falls watershed provides several examples of suitable beaver habitat, you won’t find them everywhere. “There are still patches of unpalatable vegetation and undesirable habitat that occur throughout the area.” When it comes to establishing a new home, they look for something equivalent to what they had in the past or better.
“There are no beaver here,” said Vanessa, having fully assessed the area and we continued up the trail.
Forest Diversions
We headed deeper into the woods, following the muddied trail along a ridge above the creek. The trail weaved through the Douglas-fir trees whose branches caught the late-day sunlight in a bright burst of gold.
Seeing the stately Douglas-fir trees reminded Vanessa of her husband, Andrew Merschel, a forest ecologist. “He just defended his Ph.D.,” she said proudly.
Through his research, Andrew reconstructed the fire history of Douglas-fir forests west of the Cascades, similar to the one we were hiking in. “The assumed fire return intervals are wrong,” said Vanessa. The actual fire history in this region, she explained, demonstrates a more complex reality than what has been traditionally taught.
It was fun talking to Vanessa about her husband’s forest research. It was a wonderful diversion. But we were there to talk beaver! “I want to know more about your research,” I said, as we moved slowly up the path.
Unsuitable
We hiked past another unsuitable spot for beaver—a site heavily forested with desirable alder trees but that was also laced with undesirable stinking currant. No sign of beaver.
Then the trail widened, curving away from the South Fork Alsea River, and began following the bank of Peak Creek. Here our luck changed.
Much of Vanessa’s research centered around identifying beaver activity, so as we neared an access point on Peak Creek, Vanessa led me down to the water’s edge to look for beaver sign.
Beaver Sign
Vanessa explained that many people assume that if they don’t see dams, there are no beaver present. But, as Vanessa made clear early on, not all beavers make dams. A lot of them don’t need to. So, to assess beaver activity we need to look for other signs of their presence.
Vanessa climbed down to the water balancing on logs to reach out into the creek where some branches of western redcedar hung over the water. She pulled at the branches, inspecting the tips of each branch until she found what she was looking for.
She directed me to come take a look. The end of the branch she held in her hand was clipped with clear beaver incisor marks. Looking at the branch I imagined a beaver grasping at the branch and snipping it off with its big front teeth, then eating the outer layer of the branch, as Vanessa put it, like eating corn on the cob.
Vanessa noted that clipped branches can be found up and down creeks where beaver reside, but they can be tricky to spot if you don’t know what you are looking for. People often make the mistake of just looking near the waterline, Vanessa explained, but water levels change all the time, so what is unreachable one day for a beaver might be perfect during high flows.
Feeding stations, a collection of cut limbs along a shoreline or in a protected area, and food rafts, a bunch of clippings floating in the water, are other signs of beaver foraging.
Smelly Stuff
Foraging sign is just one clue or indicator of beaver activity. I asked Vanessa if there is anything else to look out for. “Scat and scent mounds,” she replied.
Scent mounds are territorial markers beavers create out of mud and detritus. They essentially pile up these materials along the shoreline or island in the water and deposit castor, or castoreum, a strong-smelling substance released from specialized glands.
“What does it smell like?” I asked.
“BBQ sauce and vanilla,” Vanessa said. She explained that she often brings castor with her to outreach events and asks people what they think it smells like. BBQ sauce and vanilla are the most common responses. “Castor glands are used to provide ‘natural’ vanilla flavor to ice cream,” Vanessa remarked. Later, a quick google search reveals that beaver butt secretions are used for flavoring in many different food products.
Beaver scat, on the other hand, is less smelly. “Imagine little cylindrical balls of sawdust…sitting in a pool of water,” said Vanessa. It is rare to find beaver scat because of their semi-aquatic nature. “You only see it where they are active,” Vanessa remarked.
We didn’t see any scat or scent mounds during our hike.
Beaver Dens
However, a commonplace to find scat, if you find it at all, is near a beaver den. A beaver den is essentially the home of the beaver. Beavers use their dens to rest, hide from predators, and raise their young
Beaver den structures in the Pacific Northwest are not usually lodges—dome-shaped structures built with sticks and mud—like are seen on nature shows. Rather, beavers in Oregon, and neighboring states, often dig into the banks of a stream or river—creating a “bank den”—often choosing sites under trees with roots that provide an extra element of structure and protection. This is a more practical configuration in constrained waterways in Oregon than a lodge. Fluctuating water levels also means that “most colonies will have multiple dens.”
Vanessa and I looked to see if we could find a den under the cedar tree that had been munched on, but there wasn’t any clear opening.
I asked Vanessa about the size of the den, as we prodded around the riverbank. “They are about a foot wide” at the entrance, said Vanessa; and “chambers are actually small.” To find the dens, she usually uses a meter stick to wiggle underneath a bank. “The tunnel will go into the bank and then will cut up at an angle,” explained Vanessa.
Aging Sign
Having sufficiently checked the area for beaver sign, Vanessa and I decided to continue on the trail. We were hoping to reach Green Peak Falls, the turnaround point for our hike before dark and we were losing light fast.
As we clambered our way up, Vanessa told me more about her research. “Right now, I am conducting a 5-year beaver dam ecology study in this basin,” she said. “We visit the same sites every year to census of all the dams and beaver activity.”
“We will note all the different types of activity,” Vanessa went on… and “give an age status based on the newest sign identified.” She noted how the clipped cedar branch we had inspected earlier had a lot of “black spotting.” This suggests that the clipping was at least a year old. On the other hand, “it if is clear white,” explained Vanessa, which indicates “they are actively there.”
Chatter
As we walked, I noticed a medium-sized log on the trail that had been “chewed into.” Beaver? I thought. No. Upon closer inspection, the markings had no incisor imprints. The tree wound was human-inflected, Vanessa assured me.
Having seen similar markings before, I asked Vanessa what was going on. The markings are called “chatter,” she told me. Beaver will sometimes girdle a tree to wear down their incisors that continue to grow throughout their lives, or possibly to bring down a tree to access more food. In this case, the beaver is doing a lot of “chewing and spitting” and “a huge pile of woodchips” will build up at the base of the tree being cut down.
Vanessa and I “chattered” on.
Should I Stay or Should I go
Before long we reached the stairs that lead to the base of Green Peak Falls. We could hear the rushing waters and paused to finish our conversation before heading down.
“There is another thing with beaver,” Vanessa stated, “just because they occupy a site doesn’t mean they will remain there.”
The duration beaver typically occupy a stream reach and why remains uncertain. “They are all over the map on how long they stay at a site,” Vanessa explained.
The movement of beaver within a watershed is something Vanessa is hoping to find out with her future research. “We have some short-term studies,” she explained, but not enough to really understand what is happening in the bigger picture.
Part of the issue is that beaver dams in Oregon tend to be ephemeral. “By springtime, only 20-45% remain intact from the previous fall,” Vanessa remarked about her study in the Coast Range. And “they only rebuild 7-30% of the time.” More often beaver choose to build a new dam in a new location.
For her study area, “The total number of dams has been consistent at the landscape level over time,” said Vanessa. But much of beaver colonization patterns remains a mystery in response to dam failures. Will they stay? If they stay, will they rebuild? Or will they go and come back later in the year? There is much still to figure out.
Vanessa told me about a year when she surveyed her sites, and all the dams failed at one of them, but the beavers remained and didn’t rebuild. But a tributary or two over, another group of beavers constructed 16 new dams. Why? “I don’t know,” Vanessa responded.
But she hopes to find out!
Waterfall Mischief
Green Peak Falls was raging when we finally made our way down. The light of day was nearly gone, but I attempted to capture a photo of the falls anyway.
“I like Green Peak Falls better than Alsea Falls,” Vanessa remarked. Then turned and wandered over to the water’s edge. Vanessa was in her element as she balanced on rocks and logs in search of beaver sign. “Sometimes you see chewsticks that came down the waterfall,” she sighed.
After a few minutes of searching to no avail, Vanessa joined me, and we stared up at the cascading falls.
“The pool right above us…” began Vanessa, “I relocated a few beavers to a small tributary above it” She went on to tell me how the male of the pair (the female had died) would leave the release site and come down to the pool just above the falls. “He would hang out for days and then go all the way back up,” Vanessa reminisced. He never headed any further downstream. “Maybe he was too chicken to go around the waterfall,” Vanessa speculated.
I asked Vanessa how beaver typically handled waterfalls. “They do go around them,” she said. “Most of the time they will figure out a way to navigate around them.” However, she mentioned hearing about an unsuccessful beaver relocation where the beavers went over the waterfalls and died. “I have never seen the problem,” she said; “Maybe we have a better batch of beaver…”
Hopes for the Future
Darkness was really setting in now, so we decided to turn around and head back. As we walked, Vanessa talked more about her beaver dam ecology study and her goals for the future.
“We are in season four of data collection,” she said. After year five it will be intensive number crunching and analysis. The goal of the study is to help land and resource managers better understand the realized beaver dam capacity of a watershed and the factors that influence dam longevity at the individual dam and beaver site scales. According to Vanessa, the current popular model used to predict dam capacity tends to overestimate, making it seem like problems exist even when there isn’t one.
“No one knows how to best manage watersheds to promote beaver,” she continued. Our headlamps were now on guiding our way over roots and over puddles as we headed back to our cars. But more recently, Vanessa told me, there is money and interest in solving that problem. After the Labor Day fires, federal, state, and private land managers, in coordination with Vanessa’s lab, discussed the need to implement a landscape-level beaver study in western Oregon. The study will ultimately include three replicate regions—the Western Cascades, the Coast Range, and Southwest Oregon—and use beaver activity surveys to document their distribution throughout these areas, in addition to other methods like radio-telemetry to track beaver movement and colonization responses to forest disturbances.
Ultimately, through this study, Vanessa hopes that some of the most basic questions about beaver may be answered, like what they need to survive, and how fire and land management may affect them.
Beaver Believer
Vanessa and I continued to talk as we walked in darkness. And before long, we were back at the trailhead and heading home.
Having spent the evening with Vanessa, I really got a sense for her passion for her work, as well as her ability to be discerning when it comes to beaver science. Many people make the false assumption that if we can just get beaver back everywhere on the landscape, we will be okay. They will fix our problems—from habitat destruction to water conservation to even climate change.
But as amazing as beaver are they can’t fix the damage humans have done to the planet. They aren’t superheroes. Though they probably would look cute in a cape. And just like the rest of the planet, beaver have and will be affected by the dramatic changes in our climate and forests throughout the Pacific Northwest.
So, as nice as it is to sing beavers’ praises, it misses the mark. To truly appreciate beaver, we need to understand them. That is the first step. And we aren’t there yet. But with the help of people like Vanessa, we might finally learn to walk the beaver walk.
Vanessa Petro is a senior faculty research assistant at Oregon State University. Vanessa earned her B.A. in Conservation Ecology from Sterling College in Vermont and her M.S. in Forest Science from Oregon State University.