Dogs bark for many reasons, but when you’re gone, loneliness and boredom are usually at the heart of it. Separation anxiety occurs in a very small number of dogs, but if that were the case here, you’d normally see other symptoms (having accidents, destructiveness, being very clingy when you try to leave).
There’s the group of people who’ve reinforced barking, because whenever they hear a noise outside they ask urgently “Who’s there? Who’s there?” inciting the dog into a barking frenzy and rewarding them with either laughter or praise. A cool game until you’re dog barks at everything he hears without you having to say a word.
But more often than not, dogs who bark while their owners aren’t home have learned that barking gets them what they want, just as a trained dog learns that doing a “sit” earns them a treat or praise. It’s worth taking note of what your reaction is when you’re home and your dog barks at you – do you produce a treat, play with him, or run to open the door so he can go outside and play? Housebreaking issues are exempt from that last example. Teaching your dog that barking doesn’t cause you to spring into action will go a long way in extinguishing the behavior.
For the times when you do leave, make sure that your dog is suitably exercised and has a few cool toys to play with while you’re away. Don’t allow him access to windows where he might see people or dogs pass by, because that kind of “TV” viewing encourages barking every time someone passes by your home.
And speaking of being away, make sure that your goodbye is brief and unemotional. Avoid cue words that trip off the behavior you don’t want; for example, if your last words before leaving are always “Mommy misses you”, simply stop saying it. Fifteen minutes before leaving, turn on the or radio for white noise, and give your dog a dog “pacifier” in the form of a stuffed hard rubber toy, and skip the long goodbyes. Eventually, your dog should look forward to leaving so he can have his reward.