Same as above.
All you really need to do is to make sure that all of your bags and tent are closed if you're not around or are doing something else. I'm convinced they use teamwork. If you're just sitting around your camp, one will jump up on a rock near you. When you turn to look, and think to yourself, "Don't you dare try to grab my food," chances are his buddy is already trying to find a way into your pack. Am I the only one who notices this?
They won't "rip open" your pack, but they will climb inside if you leave it open. I've never seen one actually inside a tent, but they do investigate.