Jack is so incredibly unused to the cold because hahahah the hot Caribbean is his natural habitat and this sucks. Otherwise he'll do his best to stay away from all you insane, murderous people and will hide. I can see him eventually camping out around the pine trees near the meadow/river and avoiding the mammoths like the plague. Being harassed by geese will most likely be a Thing too.

If someone corners him, Jack will defend himself. Otherwise, if someone proves to be helpful or friendly, he'll most likely try to help back. I'm really up for anything!