Mad, mad dogs

Do I treat our dogs badly? Is there something vital missing in their diet? Should I consider having them re-homed?These are not serious questions as our dogs are very happy, very much loved, and well looked after. But WHY do they do this to us: Chester, our Dog's Trust rescue, has taken a fancy to offcuts of mount board (and not always small offcuts either) - so much so that he made his mouth sore, and I now have to be much more careful with my recycling stuff in the studio. I've posted this photo before, but you can see he does rather like a sizeable piece! And the border collie is Whisper, and he's developed a couple of strange tastes. He discovered my tiny gift boxes and over a few days (before I noticed what was going on) he helped himself and took them outside to bury in the garden. Just the gift boxes, nothing else. And then recently, it's brillo pads - you know, those soapy wirewool pads for scouring saucepans. He's been helping himself, taking them off to his bed and tearing them to shreds. His feet were what gave it away - rust coloured when he found an old one, and pink when he found a new one!! I shall be glad when we've finished rebuilding the kitchen and utility room and everything is safely stored away! Hmm - wonder whether I should put childproof locks on the doors?!