I don't believe there has ever been a bear encounter on the North Fork. However, I recall a few reports of food being taken, by ravens or marmots or even a fischer. If I were camping on the North Fork, I would take one.
Loc: Bishop, CA, United States
Last time I checked, the bears were pretty free to wander wherever they wanted on the mountain. While more likely (perhaps) to get things stolen by the marmots and ravens, it's not inconceivable that the bears could wander up the MR.