It won't though - the thick bags of Mountain House meals are nothing for a chipmunk to go through.

Bear canisters work in that the animal gives up after not getting a treat - it doesn't have to be smell proof - that is the beauty of it. Another example is the Ursack bag - I have woken up a couple times to find it covered in small animal poo pellets - the local squirrels were at it all night but gave up eventually after not getting in. Sure they could smell treats but they didn't get any.

A bag of plastic though...no matter thickness will eventually fail or be dragged off (Ursack bags are tied off with Kevlar cords). All an animal needs is time and at night they have plenty.

On cougars......they are more interested in semi rotten meat on a carcass. I don't worry about them ever, outside of avoiding like the plague a kill zone (and you can't miss that....the dead elk out by a river bed that stinks to high heaven).