Calgary

Busy beavers chew down trees in Weaselhead Flats for new dam, winter prep

According to Lisa Dahlseide, a naturalist with the Weaselhead/Glenmore Park Preservation Society, the beavers are hard at work to prepare food storage for winter and repair their lodgings.

Dam built to avoid spring runoff and high water, naturalist says

A North American beaver seen at Weaselhead Flats. (Diane Stinson)

It's an especially busy time to be a beaver in Weaselhead Flats.

So busy, in fact, that trail enthusiasts who have recently visited the area might have noticed that many trees have been chewed to the ground, and water in the park's popular beaver pond is shallower.

A trail of destruction left by beavers in the park. (Yves Dansereau)

According to Lisa Dahlseide, a naturalist with the Weaselhead/Glenmore Park Preservation Society, this is because the beavers-in-residence are hard at work to prepare food storage for winter — and have built themselves a brand new dam.

It led to the need for some at-home repairs, she said.

"[The new dam] altered the water levels quite a lot in the beaver pond," Dahlseide said Tuesday on the Calgary Eyeopener.

"And so, they're also doing some renovations on their lodges as a result of that … [and using] a little bit of extra trees for those two construction projects."

Water quality could have affected beaver-build

Founded in 1965 by then-mayor Grant MacEwan, the Weaselhead is one of three protected parks in Calgary — the other two being the Inglewood Bird Sanctuary and Griffith Woods Park.

Many Weaselhead hikers visit a wetland that is referred to as the beaver pond, which Dahlseide explained is fed by two streams: Spring Brook and Ravine Creek. The Weaselhead beavers initially formed a small wetland upstream from Ravine Creek.

And when construction of the southwest ring road caused concern that the build would damage the wetlands and impact the beavers who live there, it led to the province agreeing to some modifications that would make the area more habitable.

But Dahlseide said the construction still affected the wetlands — and the placement and height of the new dam, which was built last month where the water from Ravine Creek enters the beaver pond, suggests the beavers could be aware and adapting.

"The height of the dam is interesting to me, because it shows me that they're really preparing for spring runoff — that they don't want any of the water from that stream getting into the beaver dam or the beaver pond anymore," Dahlseide said.

"And it's quite interesting, because there has been five different debris flows coming from the ring road construction over the last couple of years.… So perhaps they do have some thought about water quality as well."

The benefits of beavers

Beavers have their benefits.

For example, their dams, which are built to provide a habitat and protection for their young, also create ponds and wetlands that provide habitats for wildlife, and water moving through them is purified.

"At the Weaselhead Preservation Society, we honour the beaver. We want to promote coexistence with them, because we recognize that they are a very critical keystone species," Dahlseide said. 

"Without them, we don't have that wetland, and the wetland is what provides an ecological service to humans. And especially in that area, that wetland there is filtering and cleaning the water very close to the ring road."

The beaver pond in Weaselhead Flats. (Yves Dansereau)

Dahlseide said she isn't exactly sure how many beavers have made Weaselhead their home. 

They are crepuscular, which means active at dawn and dusk, and more elusive during the day. But she estimates there are two or three beaver families residing there, at least.

And there are many lodges in the area. Though some could be abandoned, it's also possible the beaver population is greater than Dahlseide thinks.

"It's like there's a little condominium complex down there. There's a lot of lodges," Dahlseide said. "And so there could be, potentially, quite a few beavers."

Trees a good trade-off

In spite of their benefits, beavers do cause some ecological issues.

For example, according to the City of Calgary, a single adult beaver can cut down about 200 trees in a year. 

Volunteers and the City of Calgary have protected some trees in the park from destructive beaver-teeth by wrapping mesh wire around the base of tree trunks, Dahlseide said.

Aspen trees wrapped with wire mesh to protect them from beavers in Calgary’s Weaselhead Flats park. (Frances Backhouse)

But according to the naturalist, a few trees are a worthwhile investment to keep Weaselhead's beaver population healthy and thriving.

"We don't have to sacrifice all of our trees, but I think that even sacrificing some of those trees … is a good trade-off, considering the ecological service [beavers] are providing for us," Dahlseide said.


With files from Torah Kachur and the Calgary Eyeopener.

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