Referential aspects in the vocal repertoire of bonobos (<i>Pan paniscus</i>)
The complexities of animal communication continue to be investigated. However, the potential for referential communication in nonhuman great apes' vocal repertoire has only been studied in chimpanzees' (Pan troglodytes) food vocalizations. The current study aimed to examine whether bonobos' (Pan paniscus) food vocalizations contained referential aspects. Vocalizations were collected from one bonobo while feeding on one of six different food types. These vocalizations could be significantly distinguished based of food type when using a four-variable model containing low frequency, delta time, average power, and energy. They also could be reclassified into the correct food type based on these variables on a consistent basis, and most food groups were significantly distinguishable from each other. Consequently, this participant's food vocalizations suggest that bonobo food vocalizations contain information based on food type. However, this does not ensure referential vocalizations. Importantly, this study did not examine whether listeners used this information or if these food vocalizations were intentionally elicited. This study raised many important questions regarding the study of referents in nonhuman primates. First, it demonstrated the complexity of examining referents in a nonhuman species. This included aspects related to initial assumptions, such as whether or not one is starting from a standpoint that great ape and human communication is continuous. Equally difficult is setting up or finding a situation in which you can expect a one-to-one correspondence between a stimulus or setting and one specific referent. Finally, even with a sound methodology, the question of what statistical requirements should be required in order to prove a case for nonhuman referential communication remains unclear. All of these considerations have large impacts on the interpretation of referential communication and must be scrutinized deeply before any conclusion regarding nonhuman great ape vocal referential capability can be made.