There can be several different causes or triggers for excessive barking in a dog. Loneliness is one of the more common causes for this problem. If a dog feels that he is not getting the attention that he deserves then he may bark simply to get that attention.
Another possible trigger for excessive barking is separation anxiety. Separation anxiety occurs when a dog is terrified of being without his owner. This behavior manifests itself in many different ways and can include excessive dog barking. The dog may begin to bark significantly when he thinks you are about to leave home or just after you have left.
Territorial dog barking is another common trigger. This occurs when the dog barks for the specific purpose of protecting his territory. In this case, a cycle of bark and reward behavior is often established.
Other possible triggers for dog barking may include a desire on the dog's part to play, the issuance of a threat to someone that the dog perceives to be an intruder, fears and phobias, reactions to specific environmental stimuli and in some cases, illness or pain. Barking can also be related to age, breed or individual predispositions.