I know with the ferals when they eat bark and tree limbs they do it for roughage in their diet. When I started adding mashed cooked green beans to their food, they quit eating our trees.
Now I feel better because Spike does that sometimes (chew at my wood furniture)! Now I know that I am not the only one with a cat who does that sometimes.
I took a look in his mouth while he was actually being good (for once) and I saw one of his little teeth still coming through. And he doesn't usually chew on stuff like this, we just riled him up so much. His real love is to chew on PAPER!