And maybe a couple shiny rifle cartridges or a wrist watch if you left one unguarded overnight at your campsite. They collect all sorts of stuff. Esp. bones (to the delight of paleontologists).
I have seen these midden in the crotches of saguaro cati in AZ, in crotches of locust trees in Kansas, in barns in Oklahoma, under the hoods of cars and trucks that have stood still too long, and all kinds of places, but mostly around any sort of rock formation.
The really old ones develop varnishes of pee and poop with pollen and other interesting things embedded. From that you can tell a lot about the climate and biota of the surrounding area going back to the day of cave bears and ground sloths.
I have a couple of hypotheses about how these animals may shape the surrounding ecosystem, but have not been able to validate them with preliminary data.
Rattlesnakes love to hunt around them, so keep an eye out for them as well.
