About a year ago, Dad had seen an impressive beaver dam in Glacier National Park. Last Sunday, he wanted us to see it. Because it’s the middle of winter and the snow is deep, we needed to use snowshoes to get to the dam. After following a cross-country ski trail near lower McDonald Creek, we found the dam. The water in front of the dam was shallow with a deep pond behind, where the beavers could build lodges and swim all through the cold season.
Why do beavers build dams? The sound of running water stimulates the beavers to build. The shape of the dam depends on the strength of the water’s current. In still water the dam is relatively straight and in stronger currents it is somewhat curved. The one we saw was somewhat curved. Mainly the dams are used as protection against predators such as wolves, bear, and coyotes. It also provides easy access to their stored food in winter. They only build at night, and can rebuild a destroyed dam overnight.