Contact calls of zoo and wild southern white rhinoceroses do not differ acoustically

Large mammal species are declining globally, and zoo populations may help support or re-establish wild populations through reinforcement or reintroduction. However, zoo environments differ from natural habitats, which may alter behaviours, including vocalisations, potentially affecting social interactions in relocated animals. Here, we investigated whether the acoustic structure of southern white rhinoceros' (Ceratotherium simum simum) contact calls, 'pants', differs between individuals from zoo and wild populations, as well as between four separate wild and zoo populations for which we had sufficient data to investigate population effects further. Our data set included pants from 43 individuals recorded across five European zoos and four African wild populations. The results did not reveal any marked differences between the pants of zoo-housed and wild individuals or between individuals from different populations. We suggest that the lack of vocal divergence is likely due to the vocal repertoire being innate, potentially enhanced by the low genetic heterozygosity of contemporary southern white rhinoceroses. Our study contributes to the relatively limited body of the literature examining population-level variations in vocalisations among large ungulates and megaherbivores. The lack of acoustic structure in vocalisations across populations can potentially facilitate the translocation of individuals without risking disruption of social cohesion and reproduction success.