In short, Ralph reproaches Jack because he feels Jack has been shirking all other responsibilities, and encouraging his hunters to do the same, in order to pursue his obsession with hunting, which hasn't yet delivered results.

Why is Jack hunting and is Ralph's reproach justified?

In Chapter 3 of Lord of the Flies, why is Jack hunting, and is Ralph's reproach justified? ... Ralph is right that Jack's overemphasis on hunting has hurt their chances of rescue. Even if Jack had wanted to hunt, he could have left one or two of his hunters at the fire to make sure it would not go out.

Why do Jack and Ralph split up?

This split is a result of growing tensions between Jack and Ralph. Ralph has continued to try and remain civilized, though life has gotten harder and harder for the boys stranded on the island, left to fend for themselves. Meanwhile, Jack has become more and more savage, concerned primarily with hunting and killing.