How did Jack act at the feast in Lord of the Flies?

"Then dog-like, uncomfortably on all fours yet unheeding his discomfort...." "He closed his eyes, raised his head and breathed in gently with flare nostrils, assessing the current of warm air for information." And... "Jack himself shrank at this cry with a hiss of indrawn breath; and for a minute became less a hunter than a furtive thing, ape-like among the tangle of trees."