I moved on to the den of crap under the sink, sifting through all the random, miscellaneous cleansing products, shoe polish tins, and additional tupperware (!), throwing out a great deal of it, but also noticing a good many more of the little turds I had first seen on my pantry shelves. When I'd removed everything from beneath the sink, I could see that there is a large hole in the bottom of the cabinet for my sink's pipes, and that there is plenty of space there for a little critter to have easy access to my home. This was also the place where the turds were the most concentrated, so I imagine my little roommate uses this hole as it's primary mode of entry.
I inspected the various boxes and bags of food in my pantry and couldn't find any indication that a feast had taken place; nothing was nibbled into or messed up. I wonder if it came in here hoping to find a decent meal, and when confronted by spelt pasta, jars of pickled beets and brown rice, left in disgust.
(Thank goodness I didn't have to deal with my mouse like gritona had to deal with hers)