"It's one of those situations where you don't really know what you will do or how far you will go until you are in it. It's best to be thankful you're not in a situation where you have to choose and hope you don't land in such a situation. An old veg friend of mine had no problem admitting he'd eat other humans if he had no other choice (in reference to a flight crash where such a thing has happened)."
This raises another ethical dilemma. If a vegan had to choose between eating a wild pig (or crab or sea turtle) or eating a fellow castaway to survive on the desert island, is cannibalism better or worse than mere carnivory on the vegan scale of values?