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Beaver Dams

Beavers can make impressive dams. The tallest I've seen was at least 12 feet high,

and I've seen them maintain a dam 275 feet long

But we should be careful when we use the same word to describe what people make and what animals make. We put too much of our emotions, not to mention grit and determination, into what we make, especially when the finished product is something so massive and landscape changing as a dam.

We have no way of knowing how beavers regard a dam and the art of dam building. Most people who write about beavers and dams credit the animal with a large measure of forethought, engineering skill, and an obsession for stilling flowing water. I disagree. We humans think of stream gradients, rates of flow, force vectors, and what might cause the dam to fail. By making a dam we make a grab for power. Beavers make a dam to make it easier for them to get food. Beavers can move faster in the water then they can on land so naturally they feel more comfortable in water.

By making a dam, they flood the valley behind the dam, making it easy to swim to trees they want to cut down for food,

and when they cut the trees down on the shores of the growing pond, they can drag branches and logs they cut into the pond and then more easily pull them through the water to build up their lodge or dam (double click the Google Video box below the photo to see a 10 MB video of the beaver working on the dam)