No way the muskrat could have been reduced to bare bone in that amount of time...no way a fish could chew a hole into plastic that thick IMO.
If the water was warm enough, maceration could have reduced the carcass to bones if the muskrat suffocated in the raft or someone shot the muskrat on the raft with a shotgun. I do like the explanation about pulling the bones up with the raft and them getting caught in a large hole if it scraped the bottom as you brought it in. How about a snapping turtle cleaning off the bones of the muskrat and potentially causing the damage?
Edit:
O.k. scratch the theory about dregging up the bones. It wasn't mine anyway.
