Beaver Dams

• Beavers flood areas for protection from predators, for access to their food supply, and to provide underwater entrances to their den. Flooded areas also wet the soil and promote the growth of favored foods.
• Beavers living on water bodies that maintain a constant level (e.g., lakes, large rivers) do not build dams.
• Dams are constructed and maintained with whatever materials are available—wood, stones, mud, and plant parts. They vary in size from a small accumulation of woody material to structures 10 feet high and over 165 feet wide.
• The feel and sound of flowing water stimulate beavers to build dams; however, they routinely let a leak in a dam flow freely, especially during times of high waters.
• Beavers keep their dams in good repair and will constantly enlarge the dams as the water level increases in their pond. A family of beavers may build and maintain one or several dams in their territory.

In cold areas, dam maintenance is critical. Dams must be able to hold enough water so the pond won’t freeze to the bottom, which would eliminate access to the winter food supply.

This information was provided by the Washington State Department of Fish and Wildlife, Russell Link, and Michael Holmquist

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