Beavers are amazing creatures. They build dams that back up water into ponds that expand their domain into willows and trees along the edge of the water, which allow them better access to forage safely along the bank. The same willows in this scene are their principle food source and also used to make the lodges which provide shelter for them during the cold winter months. In the foreground of this image, you can see mud on both sides of a deep channel they dig out so they can swim underwater to get to the willows with added protection from predators.