I checked your site which is chock full of praise for the "daring explorer". Anybody that goes into the North American woods carrying a riot shotgun is not an expert in my book.
A shotgun is not necessarily a bad choice of tool. Ruggedized riot guns do have the advantage of being tough.
However, you do need to pay attention to your loads. Personally I would carry mostly birdshot for taking small game and birds on the wing, with a few rounds of heavier shot (goose shot)for taking slightly bigger game and a few solid slugs for Deer and self defence against Bears and Humans etc.
Probably load the magazine as 1 birdshot, 1 goose shot and then solid slugs.
Personally I would have taken one look at the porcupine and then shot it.
Dinner.
Yum, yum.