They just want to play There are occasions at which the dog will start barking when they are playing. This is again one of the more common reasons at which dogs want to bark. The dog can be barking happily when it is playing with their favorite toy, or if they are in the park, running together with its fur friends. It can also be barking when you signal the intention to bring them out for their regular walk. This is typically categorized as a harmless bark, but it is also important that you limit this behavior and train your dog not to bark.