Probably a skunk. They'll gorge themselves if they think they can get away with it. It's just a guess though, since I can't look at tracks and other stuff.
Either way, get a live trap, put some cat food in a small bowl (in this particular case, use canned cat food, nothing fish flavored) and put the bowl in the trap. If it is a skunk, you'll have to put it down from a distance of course, I've not figured out a good way yet to get close to the trap to pick it up and relocate the critter without having to sleep outside for a week afterwards.
Next, look closely around your coop/pen/run for where it's digging under (if that's how it got in), or just for any clues to how it got in, then figure out how to critter proof your coop from there. Skunks will dig, and are extremely good at it, but they're just about useless at climbing, but can in a pinch (their very long claws makes it hard for them to climb anything very well).
