Individual vs. Non-individual acoustic signalling in African woodland dormice (Graphiurus murinus)

Animals that live in cohesive groups often use social calls for long-distance communication, particularly in low-visibility habitats, whereas other call types are only used to communicate over short distances. According to the "distance-communication hypothesis" only the former should encode individual information while the latter should not because individuals are in visual or olfactory contact when calls are broadcast. We used the African woodland dormouse Graphiurus murinus, a social rodent whose vocal repertoire is still poorly known, as a model species to test the hypothesis that long-range but not short-range calls will structurally differ across individuals. By conducting controlled video- and audio recordings in captivity, we associated calls to non-vocal behaviours in G. murinus and selected two call types (contact and aggressive calls) that clearly served long- and short-range communication respectively. In agreement with the distance-communication hypothesis, only contact but not aggressive calls differed significantly among subjects. Although we did not test the actual function of such variation, the latter provides a structural basis for the transmission of individual information. This is the first time this hypothesis is tested in a small non-volant mammal. Our study also provides the first description of acoustic behaviour in G. murinus.