Dear Dr., My 5-year-old Lhasa Apso has picked up a habit of chewing zippers. We've recently had to take four coats to the tailor and replace two gym bags. He's also chewed the rivets off of jeans. We give him plenty of rawhide chews and he has a playmate -- our 7-year-old Shih Tzu -- but nothing seems to distract him from his zipper habit. Any suggestions?