On Top a Propane Tank
The actual sleeping area of the pack rat nest was under the tank which sits on a two inch raised lip. The tank was too heavy to move, so I could not get a picture of it. What you are seeing is the food store, primarily mesquite beans and pieces of quail bird block on top of the tank.
The tank is tall and too smooth for even a pack rat to climb up, but notice the convenient branch above the tank. One rat carefully climbed the tree carrying a single piece of food; lowered itself on the branch; dropped onto the tank; carefully hid the morsel under the tank cover; and then did the same thing a few more hundred times! If anything pack rats are resourceful.
We trapped the pack rat, screened off the bottom of the tank, cleaned up the food store and trimmed the tree - problem 100% solved - no poison bait needed, no reoccurring problem.