Dog barks vary depending on context

Ray Coppinger once famously (within my circles anyway) wrote that dogs basically bark for no reason [1]. Prof. Coppinger is a man for whom I have the utmost respect; indeed, his book, Dogs: A New Understanding of Canine Origin, Behavior, and Evolution, is one of the reasons why I'm in this field in the first place. Having said that, his assertion that dogs bark for the hell of it missed the mark, in my view. Recent studies out of Hungary have shown quite the contrary, in fact.

For instance, one study confirmed that humans, even 'non-doggy' ones, are able to correctly identify the emotional state of a dog based on the bark (aggressive, playful, happy, scared, or sad) [2]. Another study showed that we aren't quite so good at correctly identifying the individual dog barking, though. That depends a lot of the kind of bark that the dog is making [3].

A 2010 study by the same research group recorded dog growls in three different situations: during a play session, reacting to a threatening stranger, and guarding a bone from another dog. Then, different dogs were placed in a room with a dog cage that had speakers in it. A bone was sitting outside of the dog cage. When the dog approached the bone, a recording of one of the growls was played. Dogs were less likely to take the bone when they heard the "don't touch my bone" growl than when they heard the other growls [4]. This may mean that dogs are able to understand the context of the growls it hears from another dog.

Dogs don't bark for no reason; they are certainly saying something when they vocalize. However, it is possible that dogs sometimes bark just because other dogs are barking [5]. Anyone who lives in a suburban street with a dog in each backyard has probably experienced this phenomenon whenever the garbage men or mailmen come.

References

1. Coppinger, R., Feinstein, M, 1991. 'Hark! Hark! The dogs do bark...' and bark and bark (why dogs bark). Smithsonian, 21: 119-128.

2. Pongracz, P., Molnar, C., Miklosi, A., 2006. Acoustic parameters of dog barks carry emotional information for humans. Applied Animal Behaviour Science, 100: 28-240.

3. Molnar, C., Pongracz, P., Doka, A., Miklosi, A., 2006. Can humans discriminate between dogs on the base of the acoustic parameters of barks? Behavioural Processes, 73: 76-83.

4. Farago, T., Pongracz, P., Range, F., Viranyi, Z., Miklosi, A., 2010. 'The bone is mine': affective and referential aspects of dog growls. Animal Behaviour, 79: 917-925.

5. Lord, K., Feinstein, M., Coppinger, R., 2009. Barking and mobbing. Behavioural Processes, 81: 358-368.