Something's Been Eating Me...

Or really, something's been eating my garden!

I've been blaming the chickens. I let them out of their run in the evenings to free range in the back yard and figured they saw something tasty in there and went for it. My romaine plant is but a stalk and my bean plants have been nibbled down to the stems. Luckily, those are the only two things that it's been going for. I was able to deduce through incredible detective work and sleuthery (you know, like being a sleuth) that is was NOT the chickens that was in my garden. 

There was a bag of sunflower seeds that I'd left out and when I came back something had torn it open - but the chickens hadn't been out! So I'm brainstorming ways to catch whatever it is, or shield my yummy stuff from him/her and mention this to Mr. Brown. He cuts me off, "There's a groundhog". 

He's seen this thing for months and never told me! He smokes and I do not so he spends a bit more time outside quietly than I do. When I'm outside there's usually a show tune or two along with a running dialogue between myself, Georgia, and the chickens.
It seems this fella was here last summer too but we had a dog then. The dog would run the groundhog off when he got too close. The dog then ate everything in my garden. Dog's gone now!

So now the question is - how do I keep this rascal from ruining my harvest??