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Leave it to beavers

BANFF – Beavers are nature’s engineers but have long been persecuted for the damage they do to human infrastructure.
Credit_Vanessa Carney_web
Beavers play an important role in regulating the flow of water during periods of droughts and floods.

BANFF – Beavers are nature’s engineers but have long been persecuted for the damage they do to human infrastructure.

A multi-year program involving the Miistakis Institute, a research institute specializing in evaluating complex environmental problems, and Cows and Fish Alberta Riparian Habitat Management Society, wants humans do a better job living with beavers.

The long-term plan is to help beaver populations recover, but first, researchers hope to convince land owners and managers about the benefits beavers create for watersheds and the ecosystem as a whole in a bid keep them on the landscape instead of killing them.

“The whole premise of the program is how can we coexist with beavers harmoniously, but still mitigate some of the headaches they can cause,” said researcher Holly Kinas at the Bow Valley Naturalists’ kick off to the 2018-19 speaker series on Oct. 23.

In building dams to block streams to create ponds and wetlands, beavers provide many valuable services for the ecosystem, such as storage of water during droughts and floods, creation of habitat for many wildlife species, and improvement of water quality.

However, along with the ecological benefits they provide, beavers are also known for the challenges they pose to landowners when they cause damage by flooding roads, plugging culverts and taking down prized trees.

When this happens, the solution more often than not is to simply kill them by lethally trapping them, blowing them up with dynamite, or shooting them.

That’s where Miistakis and Cows and Fish come in.

They’ve been engaging and educating landowners on the tools available to help them coexist with beavers, which is Canada’s national emblem. They include pond levelers that regulate water levels to minimize risk of flooding, and culvert protectors, which include exclusion fencing, to create a barrier and prevent beavers from plugging culverts.

Kinas said these are some solutions to some of the challenges that may arise, noting every site is unique and every tool varies in its effectiveness.

“Surveys have found that there is support for co-existence with beavers, but things must be addressed,” she said.

An average beaver colony typically has one pair of adults, which have two to four kits every year as well as the surviving young from the previous year.

“It’s interesting that the young ones don’t actually disperse until they’re about two years of age because they take those two years to kind of apprenticeship under their parents,” said Kinas.

“That’s a really critical time in their life, when they actually learn how to build these dams and how to build these lodges effectively.”

A prosperous beaver family can have multiple dams and usually one to two lodges.

Constructed of sticks and mud, the lodge is usually found away from shore so that predators cannot get at them in summer. In winter, mud on the lodge freezes and forms a fortress against predators that venture across the ice.

After flooding the landscape, they usually don’t travel much more than 30 metres away from the water’s edge.

“There’s a really high risk of predation when beavers leave the water,” she said.

Grizzly bears have been known to prey on beaver, as one longtime Banff resident discovered first hand in the summer 2017. Leslie Taylor recalls watching a famous female grizzly bear, known as No. 148, dig into a beaver lodge at Second Vermilion Lake.

Bear 148 – later shot dead by a hunter in B.C.
last fall after being relocated from the Bow Valley by provincial wildlife authorities – had been in the area eating suckers and reportedly muskrat.

“It was one of those things we get to experience here in Banff that you don’t expect to see,” she said.

One of the things that struck Taylor was bear 148’s total concentration on digging into the lodge, sending sticks and clods of mud flying in all directions.

“The other thing that struck me was imagining what it would be like inside the lodge to see that coming at you,” she said.

Taylor did not see the grizzly bear consume any beavers, but initially thought the worst when she had not seen any beaver activity there after that.

But, she said she had a different viewpoint on the situation after speaking with Kinas last week.

“She said if beavers get a really bad scare they sometimes desert the area,” said Taylor, noting they may have escaped through an underwater hatch.

“The fact that I haven’t seen work going on at the dam may not mean they got eaten that afternoon.”

Researchers say that recovering beaver populations will help increase and stabilize water storage at a watershed scale, which will help with adaption to climate change.

Beaver structures capture water and slow the movement of water downstream, allowing for groundwater to recharge.

Ultimately, this means two to ten times more water in streams with beaver ponds versus those without, researchers say.

“We all know flood and drought are becoming more frequent and more severe. Beavers are not the silver bullet to this problem, but they can certainly help us,” said Kinas.

“Not only do they mitigate for drought, but they mitigate for flood as well.”

Kinas said beavers have been known to decrease stream velocity by 81 per cent.

“This is really important because it recharges the aquifer so that when you put in these beaver dams they act as speed bumps so the water actually has a chance to soak back into the ground,” she said.

With beaver ponds recharging groundwater, the water storage can turn streams with intermittent flows into streams that run all year round.

“When that stream starts to run dry at the end of August, and it’s getting hot and it’s getting dry, the groundwater will actually come and recharge the stream,” said Kinas. “Fish can’t live in a stream that dries up, so permanent flows are very important to fish populations.”

One of the most important and recognized ecological effects of beavers is their ability to create habitat.

Other jurisdictions, including several western states in the United States, have been convinced that allowing beavers to do their thing on the landscape has had significant, positive effects on their freshwater supply and watershed health.

A number of western states have also been using beavers to improve water supplies, restore fisheries, adapt to climate change and bring back endangered species that depend on the habitat that beavers create.

“They have a really progressive approach to using beavers,” said Kinas, adding work has helped salmon and trout populations, leopard frogs and trumpeter swans, for example.

The fur trade was responsible for nearly eliminating beavers in Canada, when the fashion of the day demanded fur top hats.

Europeans took a greater liking to silk top hats by the mid-19th century and the demand for beaver pelts all but disappeared. Eventually, populations began to recover, though never to historical numbers.

To encourage beavers to reestablish in areas where they have been extirpated, Miistakis plans to build beaver dam analogues, essentially a fake beaver dam that’s sometimes referred to as beaver mimicry.

These dams constrict water flow, encourage vegetation regrowth, and provide a positive signal to encourage beavers to build there.

“Our goal with this pilot project is to actually put these on streams where beavers once were before they were trapped out of the area,” said Kinas, noting there’s evidence of relic beaver dams. “If you build these, they will come back and maintain them for you.”