(Continuing with the off-topic ...)

Believe it or not, I had a backpack nearly destroyed by porcupines. It seems they are insanely ravenous for salt, so an empty backpack against a tree, with nice sweaty shoulder straps, is a primo snack. I was able to sew/tape things together and finish the trip. But it was an unexpected hazard, to say the least. (Porkys also chew wooden canoes; and munch the edges off plywood trail signs, since the glue contains traces of salt, or so I'm told. I've seen signs with two-thirds of the edges nibbled away ... "DANGER! DO NOT ...." ?????? feed the porcupines, I guess.)

As for squirrels -- they've chewed through multiple layers of nylon and plastic to get at my GORP (good old raisins & peanuts) ... at the TOP of an officially-sanctioned bear pole clad in slippery aluminum. My conclusion: if squirrels ever make an evolutionary leap and start working together, we humans are in serious trouble.