Castor canadensis
I was hiking on this trail, and decided to turn right onto a small intersecting trail. It took me to this creek, which I decided to cross on a "bridge" of sticks. As I was crossing I realized that this was a beaver dam, and that many of these sticks looked freshly cut/trimmed. I looked upstream and saw the beaver. I quickly laid down on the dam, took this picture, then changed lenses to get closer looks. Amazing; he just continued to munch on branches making his teeth look red!