Otters can be distinguished from beaver by their large, furred tail. They do not build their own burrows, and in fact often use those that have been abandoned by muskrats or woodchucks; they are also known to take over abandoned beaver dens. Otters are curious and like to play with rocks and shells; I read one blog wherein someone reported seeing one "sliding" down a steep part of the river bank! Anyone who has seen otters in the Pacific Ocean off of the Monterey National Marine Sanctuary can attest to their sense of play! They are always up for food and a good time!
The Friends of the Upper Mississippi River Refuges and Upper Mississippi River National Wildlife & Fish Refuge are but two of many organizations working to protect the wildlife in the area. These photos were taken from their websites.