The Wendigo was an evil spirit of hunger and insanity that struck during winter. It afflicted and possessed one and that person was driven towards cannibalism. A common symptom of it's progress was a craving for beaver meat, which was claimed to taste most like human. If, in dead of winter, Grandpa started staring at the kids too closely and asking for beaver meat all the time, it was a sure sign the Wendigo was taking him over. It seemed to most like to prey on family. Time to turn Grandpa out of the cabin, then.

That's the way I heard it in North Ontario.