I have had rat problems on many occasions when i lived in the south of Thailand, there were some that were living in my chest of drawers (the bottom drawer, which was not frequently accessed) and when i finally found the jerks, they had already annihilated most of my shirts but i guess I didn't care much about them because of where they were placed.

You are correct about them being clever, but their most clever tactic of all is how rapidly the replicated. I have heard estimates that despite being constantly hunted and poisoned, their numbers are easily higher than the human population of the planet. I have no idea if this is true or how they gather this information. :)