With what does Jack seem to have become obsessed?

For Jack, hunting is not an instinctive talent but a skill that he continues to develop as the story unfolds. His motives for hunting are disturbing. He hunts not for the ostensible purpose of gaining food to eat but for his personal enjoyment. Golding indicates that there is something tremendously dangerous in Jack's obsession; his expression is one of "madness" when he speaks about his desire to kill. At this point in the story Jack is not sufficiently prepared to kill, but he is approaching the point at which he can inflict mortal violence upon another, whether a pig or a person. Ralph cannily realizes this trait when he reminds Jack that the most important thing that the boys must do is to build a shelter. He implicitly tells Jack that his obsession with hunting does not help the boys' chances of survival.