Celebrating Castor Canadensis: What is a flow device?

Saving Canada's Beavers Castor Canadensis

We talk a lot about flow devices and how they can save the lives of beavers. And a lot of people ask a pretty good question: what the heck are flow devices?

The term ‘flow device’ is an umbrella for numerous types of installations, typically made with fencing and pipes, that can affect a beaver’s ability to dam, their existing dams, and the level or flow of water in and around their dam sites, all without causing any harm to the beavers.

These devices were pioneered by people like Skip Lisle, Mike Callahan, and others, and have proven effective time and time again. In conjunction with tree-wrapping, they act as a long-term solution to infrastructure damage or maintenance issues caused by beaver activity, and keep the ecosystem naturally balanced by allowing beavers to remain in the area.

The three primary types of flow devices used by The Fur-Bearers in our work are pond levellers, exclusion fences, and combo devices.

Pond levellers work by putting a large tube through a divot or hole in an existing dam (which the beavers quickly repair and seal into place). One end is surrounded by a fence to protect it from large debris and curious beavers, then sunken into the pond-side. The other end just pokes out the dam, and allows water to pass through the dam, and the beavers don’t try to cover it. This allows water to naturally move through the dam, but can be adjusted so the pond remains at a certain height (allowing for the beavers to access their caches, lodges, and so on). Video: Building a pond leveller in Ontario

Exclusion fences work by using the beaver’s building style against them. A trapezoid-shaped fence is built out from the spot the beavers would try and dam, frequently culverts, which forces them away as they move sticks into position. They are unable to build across the water flow, and quickly give up. Video: Building an exclusion fence in Ontario

Combo devices are the marriage of exclusion fences and pond levellers, and are used when a bit of both types of device are necessary.

When properly installed, these devices have success rates exceeding 90% in a 5 to 10-year span. Each device costs as little as $400 in materials (frequently materials that municipalities already have on site from other projects), and can take as little as two to three hours to build, with minimal maintenance over their lifespan.

The Fur-Bearers have built these devices across British Columbia, in both rural and urban environments, and have also visited Alberta and Ontario to train individuals and municipalities in their use.

Every flow device installed literally saves the lives of a beaver family – and you can help support our work to build more devices, train municipalities, and provide education by purchasing a limited availability Celebrating Castor Canadensis tee today. Click here for details – all proceeds go right back into our Living With Wildlife: Beavers program to help save the lives of our national icons.

Photo: The Fur-Bearers after installing exclusion devices with a team of volunteers on Bowen Island.


monthly donor(for as little as $10/month – the cost of two lattes) pleaseclick hereand help us save lives today.

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Join The Fur-Bearers today and help us protect fur-bearing animals in the wild and confinement. To become a monthly donor (for as little as $10/month – the cost of two lattes) please click here and help us save lives today. Your donation is tax-deductible.

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Established in 1953, The Fur-Bearers is a charitable, non-partisan organization whose goals are to end the commercial fur trade and promote solutions for wildlife coexistence in communities. Your donation is tax-deductible. Charitable registration number: 130006125RR0002

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