Yesterday I was putting a new float switch on my sump pump, the electric wires go through the wall to a plugin inside the garage. As I pulled the old one out, I saw what looked like a bead of brown caulking hanging out. I pulled it out the hole until a whole dead rat came out -- it was a rat's tail! It had climbed into the hole and gotten stuck, and died (fairly recently too).
It didn't make a thump either as it hit the inside of the garbage can.