Beavers causing Calgary tree troubles

April 6, 2016

By: Calgary Sun

They’re eager, these beavers — but making sure the damage is meager has the city in a fever.

Three years after the most devastating disaster in city history, Calgary finds itself fighting the latest fallout from the Great Flood of ‘13, this time in the form of giant rodents with an insatiable appetite for trees, and a path of destruction along the city’s riverbanks.

It sounds like a bad science fiction movie, but beavers aren’t exactly new to Calgary, and city officials aren’t actually sure if the total population of Castor canadensis has increased since the big washout, or whether it just seems that way.

“We’re trying to determine how many are out there,” said Tanya Hope, parks ecologist with the City of Calgary.

What has definitely changed as a result of the 2013 flood is how Calgary’s rivers flow and where the beavers are congregating as a result of fast and slow sections of the Bow and Elbow.

This year, wildlife experts say the water-loving animals are far more concentrated than before, and appear to be hoarding themselves in different areas of the city than before the flood, which basically wiped the river map clean.

“The lodges are much closer and they seem to be clumping together,” said Hope.

“On Prince’s Island, for example, where we used to have just one beaver lodge we now have three.”

That means up to 18 beavers — including adults, older offspring and kits — can potentially be found gnawing down trees in the area.

That’s a lot of teeth — and because many of the areas impacted have no prior history of beavers, there’s no wire in place to protect the trees from this post-flood population, which if its anything like the beaver community prior to 2013, could number in the 200 range.

The result is extensive devastation, with reports being filed with Calgary 311 of up to 20 and 30 trees being felled in a given area.

“The flood did change the river — they’re out now in areas where they haven’t been before and the tree haven’t been protected,” said Hope.

She also says Calgary’s veteran beavers are getting smart, having learned to get around old wire protection measures, and forcing the city to go with tighter and higher mesh.

“We have to stay one step ahead of them,” she said.

You can easily spot the damage this spring all along the river pathways, though Hope says much of the serious felling actually took place in fall, as the beavers were preparing for winter. The early spring has made the destruction all too obvious.

“We knew the damage was out there,” said Hope.

In the bad old days, the city might have tried to protect the trees by eradicating the buck-toothed pests, but in this enlightened age, Calgary does what it can to live with the animals, destructive trapping being a last resort for forests in danger of being ruined forever.

Beavers are now understood to be a healthy part of an ecosystem, and their activities can help humans too — such as the dam at Prince’s lsland, that helped protect a storm water pond from being swept away during the big flood.

Instead of a beaver cull, trees are wrapped with wire, pipes are built under known dams so the city doesn’t have to knock them down, and Calgary is currently testing a new beaver-deterrent spray that can be applied to a lot of trees in a very short time.

And on Tuesday, the city released a video for private property owners along the rivers, showing them how to wrap their trees to prevent loss to the roving rodents, which include so-called “transient beavers” which are just passing through the city via the rivers.

To keep the beavers from starving, the city only protects 80% of trees in a healthy forest, leaving easily replaced and regrown timber for food and rodent construction projects.

Those landscape-altering endeavours are what made Hope go from just studying Calgary’s beaver population, to really admiring the animals for their cleverness and ingenuity.

“I think beavers are amazing, and they are the only species apart from humans that can completely change the landscape around them,” she said.

“We definitely want to work to keep them here in Calgary.”

By: Calgary Sun

Your comments.

Your #1 source for forestry and forest industry news.

Built by Sofa Communications