What does Jack admit to Ralph?

Jack admits to Ralph that if he's not hunted he feels uneasy and unsafe in the jungle as if he's being hunted and something is following him

(quote from book)

"If you're hunting sometimes you catch yourself feeling as if--" He flushed suddenly. "There's nothing in it of course. Just a feeling. But you can feel as if you're not hunting, but--being hunted, as if something's behind you all the time in the jungle".