How did so many small mammal, lizard, bird, & fish bones get concentrated at Natural Trap Cave?!? Aaron has already databased >16,000 bones & teeth!!! The answer, it seems, is that packrats gather bones from the surface around the cave entrance, and then stash them in their nests along the inner rim of the cave. As they scurry around their nests (or if a rainstorm hits), they knock some of their precious treasures off into the cave, creating concentrated layers of bones.
On August 24, I presented research about the taphonomy of the small animals at Natural Trap Cave at the Society of Vertebrate Paleontology conference in Calgary. Aaron previously presented similar results at the Southeast Association of Vertebrate Paleontology Conference. Here is an article based on that talk.