The littluns have to stick together and work on the huts because there to young to hunt and because ralph doesn't want them to hunt. There also scared about what out in the woods.
Ralph and simon also stay and build hunts with the littluns because ralph doesn't agree with jack about hunting and killing animals. Ralph want to find different way to survive other than jack.
Jack is out in the woods hunting and killing animals because he thinks that's the right way to survive because the littluns and him need meat and to survive. Also piggy is with him because he is mean to piggy and manipulates him.