Muskrats are much smaller than beaver; both are rodents with large teeth for eating vegetation. This muskrat was about the size of a small (trim) woodchuck. The most noticeable difference between beaver and muskrat are the tails. Beavers have a broad flat tail, while muskrats have a thin rat-like tail. Here are the two in comparison.
I'd much prefer to see a muskrat swimming then to stumble across a dead one. Yet, this up close encounter offered a unique opportunity to study its features and to ponder its fate.