Interview with a rhino: Functionality and directionality of communication calls in the captive Southern white rhinoceros
Acoustic communication is a complex model that is most essential in social animals. Since vocalisations are considered to be indicators for social interactions, it is inevitable to be able to identify the functionality and social relevance as well as the directionality of communication calls in order to facilitate monitoring of socio-sexual behaviour and group dynamics. This study aims to examine these fundamental parameters in the white rhinoceros (WR). For this purpose, behaviour and vocalisations of 32 Southern WR (Ceratotherium simum simum) were video- and audio recorded in seven zoos using focal animal sampling. Vocal analysis focused on three call types: pants, threats and snorts. The behavioural context in which each call type was uttered and the nearest neighbours were determined. Moreover, communication networks were generated for each call type in order to analyse directionality and structure of vocal interactions. The results emphasise distinct call functions: Pants are uttered in affiliative and neutral interactions between sexes. Threats are uttered by females towards males during agonistic interactions. Snorts are uttered by all individuals equally during various relaxed contexts. Furthermore, vocal interactions proved to be unidirectional and depending on the proximity of specific group members, indicating that individuals adapt their vocalisations according to surrounding conspecifics. In conclusion, the three call types have distinct functions and social relevance in WR. The animals vocalise at a non-random level and direct the calls to specific group members. Therefore, the analysis of acoustic communication is a useful tool for illustrating group composition as well as social interactions.