The dog bark is a canine alarm call. It is a message to other members of the dog’s pack which of course includes humans if we are writing about the domestic dog. It is not meant to be a threatening noise to a stranger who happens to walk nearby. It is directed at the pack members and not that stranger.
The dog bark message is, “Be alert, there is something strange happening over here!” In the wild, it results in puppies taking cover and hiding while adults prepare themselves for action. A barking dog does not know whether the arrivals are friends or foes which is why dogs bark when their owner comes home or when an intruder is about. Once the dog knows that he is interacting with his owner barking is replaced by a friendly greeting.
When a dog attacks it does so completely silently as demonstrated by police dogs attacking men pretending to be criminals during training processes. Dog vocalisations are indications of conflict or frustration. Snarling when a dog displays its canine teeth is typical of a dog who is aggressive and mildly fearful. Growling indicates that the dog is more fearful than when snarling. The risk of attack is high. The dog is on the defensive with a high level of aggression which can drive the dog to explode into a full-blown attack at any time.
When there is growling alternating with barking it as a signal from the dog which says, “I would like to attack you (as reflected in the growl) but I think I will call up reinforcements (as reflected in the bark)”. If the dog becomes more fearful and it dominates the aggression the dog stops growling and continues to bark loudly and repeatedly. When the cause of it disappears or the pack has investigated what is going on it stops.
The continuous stream of barking that we hear by domestic dogs is not due to their wild ancestry but to 10,000 years of selective dog breeding. Wolves do bark but the barking that they make is different to that of domestic cats. It sounds abbreviated and relatively modest compared to domestic dogs. It is not particularly loud or common and it is monosyllabic. It is a staccato “wuff” according to Dr Desmond Morris. It is repeated a number of times but does not develop into the rapid and noisy barking of domestic dogs.
It appears that dogs underwent selective breeding for their barking abilities as guard dogs. This, as mentioned, introduced this rapid machine-gun fire barking into all domestic dogs. Since then domestic dogs have inherited this trait. There is one dog breed which has avoided this development. The African Barkless dog was bred to be a silent hunting dog in ancient Egypt over 5,000 years ago. The breed has never been used as a guard dog.
There was a well-known saying, “His bark is worse than his bite”. There is truth in it because the dog that barks is calling for reinforcements whereas a dog that bites is simply doing it without barking.