‘The bone is mine’: affective and referential aspects of dog growls

A number of species are considered to use functionally referential signals such as alarm calls or food-related vocalizations. However, this particular function of communicative interaction has not previously been found in canids. We provide the first experimental indication that domestic dogs, Canis familiaris, rely on context-dependent signals during interspecific agonistic encounters. We recorded several sequences of growls from dogs in three different contexts: during play, guarding a bone from another dog, and reacting to a threatening stranger. We analysed the acoustic structure of the growls and additionally performed playback tests in a seminatural food-guarding situation. We found that play growls differed acoustically from the other two (agonistic) types of growls, mainly in their fundamental frequencies and formant dispersions. Results of the playback experiment showed that food-guarding growls deterred other dogs from taking away a seemingly unattended bone more effectively than growls recorded in the threatening stranger situation. We ruled out an effect of the signaller's body weight on the subjects' responses. These results provide the first evidence of context specificity of agonistic vocalizations in the dog. We discuss the possible aspects of honesty and deception through acoustic modulation of growls.