My Sister’s Chewing Dog

My sister’s dog has been chewing on everyone’s shoes and destroyed three pairs!! My sister is not happy about this.  The dog only does this when he is not being watched, for instance, if my sister is working on the computer, the dog will get a shoe and begin tearing it apart. She asked me if I knew what could cause this kind of dog behavior. I suggested her dog might be bored and to get some strong chewing toys since some dogs have a strong urge to chew. She took my suggestion and it worked! The dog no longer chews on shoes, but he sure loves those new chew toys!!