Dogs bark, cows moo, lions roar, and rhinos…? Well, according to a new PLOS ONE study, young white rhinoceros communicate with whines, pants, snorts and threat calls.
Little is currently known about rhino communication, but detailed observations of eight young white rhinos in German zoos have provided initial insights into the development and usage of vocalizations in calves and juveniles. I interviewed lead author Sabrina Linn of the University of Veterinary Medicine Hannover and Serengeti-Park Hodenhagen, Germany, via email to find out more.
What led you to study animal communications?
SL: I have always been fascinated by animal vocalizations and by understanding animal “languages.” Vocal signals can provide useful information about the sender, for example their sex, age, social status, and even their emotional state. Thereby, learning about a species’ vocalizations can help to understand complex social behavioral patterns.
Tell us about the lifestyle of white rhinoceros adults and juveniles in the wild?
SL: The white rhinoceros is said to have a “semi-social” lifestyle. While adult bulls seem to be solitary, calves and juveniles have been observed to form long-lasting associations with their mothers. This contrasts with all other rhinoceros species, which lead solitary lives.
You characterized the vocalizations of eight young southern white rhinos in zoos in Germany. What did you find?
SL: The young southern white rhinos produced four distinct call types in different behavioral contexts: “whine,” “snort,” “threat,” and “pant” calls. Whines were mainly emitted during isolation or while close to the mother to signal intention to suckle; this call might also signal general discomfort or distress. Snorts were mainly uttered in non-social situations such as feeding or resting. Threat vocalizations were produced by the calves during the approach of group members or keepers as a mild “keep-away” warning. Pants were produced while approaching or following the mother or other group members and might serve as a kind of contact call.
The researchers used audio-visual equipment to record calls produced by the young rhinos
How did the young rhinos’ calls compare to those of adults?
SL: Snort, threat, and pant calls are known to also be produced by adults, and the calf calls corresponded in acoustic pattern and context to those of adults. The whine call, however, was seen less frequently with increasing age, and seems to be an infant-specific call.
A young rhino here produces the whine call before suckling
One of the calves you studied was hand-reared rather than suckling its mother. What did its calls tell you about the possible development of vocalizations?
SL: Analyzing infant vocalizations can help us understand the development and usage of species-specific vocalizations. In this study, the hand-reared calf produced all four call types and even used them in the appropriate behavioral context. Since the calf would have had little opportunity to learn the calls from other rhinos, this suggests there might be a strong innate component to the development of vocalizations in white rhinos. The findings support the theory that for most mammals, vocal production and usage are largely fixed at birth.
Why are rhino communications so interesting?
SL: Rhinoceros vocal communication is a fascinating area of research, not only because rhinos are one of the largest terrestrial mammals, but also because they inhabit a wide variety of socio-ecological niches, with lifestyles ranging from semi-social to solitary and habitats ranging from forest to savanna. Rhinos could therefore provide useful opportunities to investigate how socio-ecological niches affect mammalian vocal communication.
What are the next steps for your research?
SL: Unfortunately, our knowledge about rhinoceros vocalization remains very limited. It would be interesting to examine how vocalizations develop as calves grow to determine the onset of adult vocalizations and any differences between sexes. Future studies could also attempt to validate the hypothesized functions of the different call types.
Research Article: Linn SN, Boeer M, Scheumann M (2018) First insights into the vocal repertoire of infant and juvenile Southern white rhinoceros. PLoS ONE 13(3): e0192166. https://doi.org/10.1371/journal.pone.0192166
Images Credits: Fyre Mael, Flickr; Sabrina Linn; Sabrina Linn
Video Credit: Sabrina Linn