>> Not much is rodent proof/resistant-besides metal and things like Ursacks and bear canisters. <<
Even Ursack advises that sharp teeth like those from canines, felines and rodents are able to get through their material. Apparently bear teeth are more rounded than these other species.
From the Ursack FAQ page:
"Is Ursack resistant to rodents, marmots, wolves, etc? - Ursack is highly effective against Marmots and raccoons. It should not be considered wolf or dog resistant. That's because they have sharp teeth and strong jaws. Bears have great strength, but their teeth are not sharp. Other rodents have varying degrees of success. Sometimes mice can chew very small holes, but very little of your food is likely to be taken. Some species of squirrels and (we have heard) pine martens have greater success, and may on rare occasion chew holes in Ursack."