Eager Beavers

What An Increase in Beavers Might Mean for the District

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A beaver family has moved into Kenilworth Aquatic Gardens. Courtesy: NPS Capital Parks East
The District is located at the confluence of two rivers, a city built around streams, marshes and wetlands. It’s the home of 800,000 people. It is also the perfect habitat for beavers.

Over the past few years, residents and visitors have increasingly spotted the sleek, orange-toothed rodents and their activity in and around the city’s waters.

One of those places is Kingman Island, where Friends of Kingman Island Vice President Lora Nunn and her family like to explore along the shoreline, looking for what her two children call ”beaver evidence”; trunks stripped of bark; trees felled, leaving pointed stumps; dams in the water. If they are very lucky, they will spot a beaver itself, swimming in the water under the bridge between Heritage and Kingman Islands.

“They leave significant evidence on a tree that is unmistakably beaver,” said Nunn. “The kids love seeing it.”

The beaver activity is proof of a tremendous resurgence. What does that mean for the District’s environment, its wildlife and its residents?

Fashion Victims
When Europeans arrived, there were between 60 and 400 million beavers on the North American continent; by 1850, the year the top hat fell out of fashion, and with it, demand for beaver pelts, they had been eradicated from many states. They could only be found in rare pockets around what was then the nascent District.

But over the past 30 years, beavers have returned to the District in increasing numbers. They’ve reestablished themselves to about 25 percent of their pre-colonization population.

District Department of Energy and the Environment (DOEE) doesn’t do a beaver census, but frequency counts indicate the area population has actually stabilized over the last ten years. The feeling that there are more beavers in the last few years might be as much perception as reality, said DOEE fish and wildlife biologist Lindsay Rohrbaugh.

People have increasingly been outside during the pandemic. “A lot of people are just enjoying their parks and noticing the beavers,” she said.

There’s a cap on how many beavers can populate the District, experts say. First, they don’t tolerate other beavers with their areas. Second, there’s only so much territory.

“Absolute beaver numbers are always going to be limited by the fact that they can only occupy stream channel and flood plains,” agrees City Wildlife’s Dr. John Hadidian, formerly a scientist with both the Humane Society of the US and National Park Service (NPS). “That’s something that [only] extends 100 to 300 feet from the water, depending on tributary size. “

Giving a Dam
Beavers are nature’s engineers, so well-known for their abilities that a determined beaver is the logo for the MIT athletic teams, the Engineers. Beavers dam rivers and streams to create ponds where they build their underwater homes, or lodges. In their lodges, they raise multi-generation families—babies, called kits, will live with their parents for two years, helping to raise the next yearlings.

Beaver activity is tremendously beneficial to the District, said Jorge Bogantes Montero, Stewardship Program Specialist for the Anacostia Watershed Society (AWS).

Their environmental modifications can have many benefits. Beaver dams slow the flow of water, creating new wetlands that can become the ideal habitat for birds and animals like muskrats, shorebirds and ducks as well as amphibian and plant life. The dams also act as natural filtration systems, capturing pollutants and silt before they can enter the river.

Beaver activity is tremendously beneficial to the District, said Jorge Bogantes Montero, Stewardship Program Specialist for the Anacostia Watershed Society (AWS).

Last fall, he and a group of volunteers were going down Nash Run, a tributary of the Anacostia River located roughly along the 4400 block of Douglass Ave. NE. The District restored Nash Run in 2016, part of an effort to reduce stormwater erosion and flooding that also created the perfected habitat for beavers.

The project restored one acre of wetlands and more than 1,400 feet of stream, planting 99 canopy trees, more than a thousand bushes and creating a floodplain to dissipate the energy of stormwaters and to lower erosion. It mirrors the work of beavers, who create multiple pools that slow stormwaters.

The AWS team was walking upstream, focused on the area’s mussel population, when they realized the path of the stream looked different.

“I said, that’s weird,” Bogantes recalled. “I wonder why that is.” Walking up to the culvert where the tributary passes under the parking lot of New Smyrna Missionary Baptist Church, they found a big beaver dam. When they returned in February 2022, Bogantes counted up to four more dams.

Many stream restoration systems are inspired by the work of beavers, he said, but the DOEE project attracted nature’s experts in engineered waterland restoration. “The beaver dams you see at Nash Run are exactly doing that,” he said, “slowing down the water, filtering nutrients, trash, sediment. It’s exactly what we need.”

“We just have to evaluate the side effects [on] the people.”

Nice Gnawing You
While the return of beavers to Nash Run is helping DOEE meet goals such as stormwater mitigation and pollutant filtration, their return can create conflict with humans. The beavers are cutting down some of the trees DOEE planted during restoration. They’re also affecting the homes of human neighbors.

During his last visit one neighbor told Borges that he liked the beavers fine—it’s the water he’s worried about.

“The beaver is ponding, so there are big ponds getting closer to his house—the water line is probably 20 feet from the house now,” Borges recounted, “so you have to think about basement water issues, flooding that you have to start worrying [about] if you are a neighbor of those beaver habitats.”

Other neighbors also have concerns. Just a few months ago, NPS rangers at nearby Kenilworth Aquatic Gardens noticed a family of beaver had moved in and built a lodge between two large ponds in the northeast end of the park. While beavers frequently visit the park, this is the first time they’ve tried to move in, said NPS spokesperson Sean McGinty.

“It’s looking like they’re trying to make a home here, to stick around and try to possibly raise some young,” he said.

But Kenilworth Park is home to exotic species of plants and large meadow restoration sites, growth that can be severely endangered by damming. It’s technically illegal, even for beavers, to cut down trees in a National Park, McGinty said. Rangers are keeping an eye on the water lily and lotus pools and watching for any beaver engineering that could create unsafe conditions, such as blocking or flooding pathways. Rangers also want to make sure that both beavers and people remain safe as they interact; for instance, they don’t want people to try to feed beavers or touch them.

Leave it to Beaver
There are devices that can maintain water levels—pond levelers—that can also help resolve flooding conflicts, though none are yet known to be in use in the District. Trees can be protected with spray repellents, or more effectively, with wire mesh. NPS has employed the latter measure for some time.

McGinty said rangers are monitoring the situation. If there is a significant negative impact, he added, NPS might have to consider relocating the beavers.

NPS hasn’t done that in years, maybe not since the infamous beaver family moved in to the tidal basin around the Jefferson Memorial in 1999 and chopped down four cherry trees and five cedars. But McGinty said plans are being formulated should beaver management become a problem.

Rohrbaugh at DOEE said they have made recommendations to residents and contractors and even the Pentagon for beaver remediation, usually suggesting residents use mesh fencing to preserve trees. But they won’t relocate beavers.

“We don’t do that, it’s not part of our work. The beavers are meant to be there,” she said. If an area is prime habitat, she added, another beaver will likely try to stake a claim to the area anyway.

Beavers and humans are existing in a sort of a tense relationship because of their mutual effect on our built environment, said Hadidian. But we also need them to mitigate some of the problems our cities have caused, such as storm flooding and habitat destruction. “You can create win-win situations very easily with beaver,” said Hadidian.

People are becoming much more tolerant of living with wild animals, he adds. “It’s just a matter of understanding them better, understanding how to resolve conflicts and incorporate them into their lives.”

Learn about City Wild Life at citywildlife.org/. See the District’s State Wildlife Action Plan at doee.dc.gov. Learn more about Kenilworth Aquatic Gardens at www.nps.gov/keaq/