According to a new study on canine behavior, tail chasing is very similar to obsessive-compulsive behavior in humans. This study indicated that dogs who are separated from their mothers too soon may suffer from this problem and that supplementing their diets with vitamins and minerals may help. My gigantic, 5 year old German Shepherd, Bella, has never stopped chasing her tail, which usually leads to spilled coffee & a lot of yelling! I guess it's time to get some doggie vitamins!