My first reaction to any noise is to yell "who's there?" apparently... the wind in branches wakes me up, I holler. Much to the annoyance of my neighbors in their tents.
One night it was a bear... he didn't answer but I heard him walking. And then a number of yards away, one of the group shouted, and a few seconds later the bear blinked in the light of multiple headlamps as he was licking a large Bear Vault... Bear scrammed under the scrutiny of several yelling hikers and left the can, which was then moved a few more yards away from the tents.... I love the JMT, but not for the amount of sleep you get. Anyway, the only thing the bear touched other than the saliva covered canister was a little pringles can left out on a rock - it had fishing tackle in it. There was a nice big tooth puncture in the side. None of the pots, platypus bladders, tents, tarps or packs were disturbed.