While observing one of the beaver ponds, ice could be seen breaking on the surface, signaling that something was swimming underneath. When the creature reached an opening in the ice and surfaced, it turned out to be a muskrat. What made this sighting peculiar was that this muskrat was carrying something large behind it. It set the mystery object, which was nearly as big as the muskrat itself, down on the beaver dam. As it dragged the object over the dam, it was clear as day that there were two tails slipping out of sight; the mystery object was a dead muskrat!
It turns out that "Although few people seem to realize it, the muskrat, although rodent, eats a quantity of animal foods. He will eat clams, snails, crayfish, fish, frogs, reptiles, young birds, and carrion, including other muskrats." (source: North American Mammals by Roger A. Caras)