"First you take the rabbit across, leaving the fox and cabbage behind..."
me, stuffing my face with kimchi: "Hmmm?"
Foxes are omnivores. They will eat the hell out of vegetables. I know that's pedantic, that it's a logic puzzle with a handful of preconditions. But the whole reason this puzzle exists is that it's meant to be presented to you by some smug card-carrying MENSA member to show you how clever they are, and frankly the impression of their towering genius is a bit undermined by their inability to do basic research
To be fair, I've seen different incarnations of this puzzle that substitute the rabbit and fox with a sheep and a wolf instead (why a farmer would ferry a wolf across the river in the first place when they can swim is beyond me, but let's roll with it).
... except wolves, while eating more meat overall than foxes, won't turn up their noses for all sorts of fruit and grain either, leaving us back at square one.
Yes, that's tomato sauce on my face. Don't worry about it. No, really.
"You're a wolf, and you have to cross a river with a sheep, a farmer and a... cabbage? Do sheep eat cabbage? Sssshit. This is complicated."