Nothing irritates neighbors more than a dog left alone who barks nonstop all day or night. This happens because some dog owners subscribe to the "out of sight, out of mind" style of dog ownership—when they leave, they don't hear the barking dog, so everything's cool. A dog who barks when you leave does so from separation anxiety. If you want to be a good neighbor and a responsible dog owner, take steps to ensure your dog doesn't bark when you leave.
Tire Out Your Dog.
This might require you to get up from bed earlier than you like. Before you leave for work or wherever you're going, exercise your dog. A tired dog is less likely to bark when you leave. The breed, age and health of the dog determine how much exercise he needs. Take your dog on a long walk, a jog or play a long game of chase before you go out.
Keep Your Dog Busy
Offer your dog a fun puzzle toy filled with food. This works for two reasons: you're establishing a good association between you leaving and your dog receiving a fun toy and treat. And, you're giving your dog something to do while you're gone that helps relieve boredom. You can buy dog toys that you can stuff with food. Stuffing them with frozen food takes up even more of your dog's time. Take the toy away when you arrive home. Your dog might enjoy the toys and treats you provide so much that he'll look forward to your leaving.
Accustom Your Dog to Alone Time
Take some time off work to gradually help your dog become used to you being gone. This is sometimes necessary with dogs who have a more severe case of separation anxiety. Walk your dog, provide a toy and treat, and leave for a short period. The goal is for you to return before your dog has time to become anxious and bark. You might be able to leave for only 30 seconds the first time. When you return home, take the toy from your dog. Repeat the process, and leave for 30 minutes next time. Keep increasing the time until you are confident you can leave without your dog becoming anxious.
A Few Warnings
Don't leave your dog in the car for long periods. Dogs can suffer heatstroke when the weather is 70 degrees Fahrenheit and above.
Never yell or hit a dog who is barking. This only further upsets the dog and worsens the problem.
By Laura Agadoni
The Humane Society of the United States: Barking -- How to Get Your Dog to Quiet Down
ASPCA: Separation Anxiety
Dog Health Guide: How To Stop Dog Barking
Certification Council for Professional Dog Trainers: The Scoop