Why does my GSD chase his tail?

Question
If at any time my GSD is left alone in another room or let
outside for any period of time he will chase his tail. Once
he catches it he will chew on it until it bleeds. He does
this even more when we have company over and he is outside
away from everyone.

Answer
It is likely boredom.  You need to enrich the dogs life.  If he is more stimulated other times, he may accept it better when he is left alone.  If you haven't obedience trained it doing so would help.  The key to most behavior problems is approaching things using the dog's natural instincts. Dogs see all the people and dogs in the household as a pack with each having their own rank in the pack and a top dog. Life is much easier if the 2 legged pack members outrank the 4 legged ones. You can learn to play the role of top dog by reading some books or going to a good obedience class. A good obedience class or book is about you being top dog, not about rewarding standard commands with a treat. Start at http://www.dogsbestfriend.com/ For more on being top dog, see http://www.dogbreedinfo.com./topdogrules.htm

There are many other activities you can do with the dog, fly ball, agility, free form dancing, playing at the dog park, etc.  If he is left alone all day, spending the day at doggy day care would be better for him.