Well, I limbered up my Google-fu to investigate squirrel caches.
Red Squirrels are the species most likely to fill "cavities" with nuts.
Proximity to the nest was listed as a variable.
"Salting" the cavity with a few nuts was suggested.
Here is a web page discussing a Squirrel Cache Condo. The house this guy built is a beautify piece of craftsmanship. It looks like a whole lot of work. I am more of a plywood, PVC pipe and 5 gallon bucket kind of guy.
Other webpages indicated that a healthy population of Red Squirrels is closely correlated to mature, cone bearing trees.
So far, I have seen little info about ground squirrels cache activities. I can attest that they do it. I have some running shoes (New Balance, size 11), a partial roll of baling twine and a truck air cleaner that were filled up with corn by those little rascals.