Since you're referring to it only happening while you're gone, it's sounds to me like you're probably dealing with a case of separation anxiety. Separation anxiety happens when a dog does not like to be left alone, and it's a very common problem. According to the Dumb Friends League, dogs have separation anxiety when:
- The behavior occurs exclusively or primarily when he’s left alone.
- He follows you from room to room whenever you’re home.
- He displays effusive, frantic greeting behaviors.
- The behavior always occurs when he’s left alone, whether for a short or long period of time.
- He reacts with excitement, depression or anxiety to your preparations to leave the house.
- He dislikes spending time outdoors by himself.
- Keep arrivals and departures low-key.
- Make sure your dog is getting PLENTY of exercise. A tired dog is a happy and calm dog. Young dogs especially need A LOT of exercise.
- Leave your dog a piece of clothing that smells like you.
- Establish a "safety cue" that you use every time you leave. Do something every time you leave that lets the dog know you will be coming back. At first, only do this before you leave for short periods of time and then gradually increase it to longer periods of time. Some examples: give him a special toy or turn on the radio. This technique worked wonders for my parents' dog. They give him a ball with a treat in it (small Kong ball that fits a cracker in it) when they leave and now he actually looks forward to them leaving and has no more separation issues.
- The article from the Dumb Friends League also describes a technique for desensitization. Essentially, you SLOWLY work the dog up to being ok with staying alone. Please read the article for a full description.
- Punishment is not an effective way to treat separation anxiety. In fact, if you punish your dog after you return home it may actually increase his separation anxiety.
- Getting another pet. This usually doesn’t help an anxious dog as his anxiety is the result of his separation from you, his person, not merely the result of being alone.
- Crating your dog. Your dog will still engage in anxiety responses in the crate. He may urinate, defecate, howl or even injure himself in an attempt to escape from the crate. (NOTE: I personally disagree a bit with this one. In my opinion, a dog dealing with separation anxiety may not benefit from being in a crate, but it prevents him from destroying the house and hurting himself while destroying things. If you have no where else to leave the dog, crating seems like the only option to me.)
- Leave the radio on (unless the radio is used as a "safety cue" - see above).
- Obedience school. While obedience training is always a good idea, it won’t directly help a separation anxiety problem. Separation anxiety is not the result of disobedience or lack of training, it’s a panic response.
http://www.ddfl.org/behavior/separtn.htm
http://www.wagntrain.com/SeparationAnx.htm
http://www.perfectpaws.com/sa.html