Learning from Playbacks: Testing the Communicative Function of Snort and Pant Calls in the Southern White Rhinoceros

In southern white rhinoceroses (Ceratotherium simum simum), pant calls are well-studied contact vocalisations, whereas the function of frequently emitted snorts remains unclear. We conducted playback experiments with 15 rhinoceroses at three European zoos. The first experiment tested responses to conspecific versus heterospecific snorts, comparing pulsed and non-pulsed acoustic structures. The second experiment contrasted conspecific snorts with conspecific pants from males differing in age and faecal testosterone metabolite (fTM) levels. Behavioural responses—including body orientation, approach toward loudspeaker, locomotion, and vocalisations—were analysed. Snorts, regardless of sender species or pulsation, elicited uniformly low-intensity responses, suggesting limited communicative function. In contrast, pants evoked significantly stronger responses depending on sex and group setting. While males showed increased locomotion, females vocalised more, reflecting the species’ social dynamics. Individuals tested alone displayed overall heightened vigilance and vocal activity compared to those tested in pairs, emphasising the role of social context. No evidence was found for discrimination between pant calls differing in fTM levels. Our findings reinforce the communicative relevance of pants in conveying social cues while indicating that snorts may either lack species-specific acoustic markers or not be socially salient. Playback experiments thus appear as valuable tools for assessing acoustic communication in zoo-housed mammals.