Dogs bark for a variety of reasons, including to protect territory, to get attention, or merely just to signify that they feel bored, frustrated, playful or excited. Dogs with health issues such as Canine Cognitive Dysfunction or deafness sometimes bark without full realization of their behavior.
Certain factors may indicate the causes of a dog's barking. For example, if a barking dog has its tail held high and its ears erect, the barks may provide a warning or challenge. If the barking dog has its tail held low and its ears flattened, then the barking may communicate a feeling of fear.