After spending some time Googling various types of poop the other day, I was able to figure out what the critter is that's been eating my garden (today's victim: The Eggplant).
The little guys who are munching (and pooping in) my garden are Nutria. They're beaver-like creatures that are fairly prevalent in Salem (though not native). And the site I found about them said that they will pull up entire plants. Bingo.
I've been terribly agitated about my plants getting eaten, but my heart softened some when I found this photo:

Awwwww! CUTE!
I mean, I guess it's awfully nice of me to be growing veggies to feed an adorable little family of nutria. It's not like they get a CSA box delivered every Tuesday, right? Jim & I don't need the veggies. Nutria need food, too!
Nonetheless, I think I'll put up some sort of fence & see if they can find their way to somebody else's garden....