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Chimpanzee Vocal Communication

Chimpanzees are very social animals and communicate with one another in a variety of ways. One of their most noticable forms of communication are their vocalizations. Chimpanees produce a variety of calls, with over 15 identified call types. Their vocal repertoire is graded, which means that it is often difficult to identify clear boundaries between many call types. Some of their calls are loud and function in long-distance communication between different parties of chimpanzees. Others are soft and function in close-range communication between party members. While much has been learned about chimpanzee communication in recent years, we still have much to discover. Below are descriptions, recordings and spectrograms of many of their call types.


Pant-hoot

PictureThe pant-hoot is not only one of the best-studied chimpanzee vocalizations but also the most conspicuous. This call is produced in a variety of contexts and often functions in communication between distant parties. Pant-hoots can be produced solitarily or in a chorus and are often heard during socially exciting events.


Pant-grunt

PictureThe pant-grunt is a rapid series of grunts separated by audible inhalations. It is typically given as a greeting and is always directed up the dominance heirarchy, meaning that higher-ranking chimpanzees never pant-grunt to lower-ranking chimpanzees. While the pant-grunt is often produced during relatively calm social contexts, it can grade into pant-barks and even pant-screams as the threat of aggression increases. Researchers often use data on the direction of pant-grunt production to determine and keep track of the dominance heirarchy.


Rough-grunt

PictureChimpanzees produce rough-grunts exclusively in feeding contexts. They may be produced in anticipation of food, upon discovery of food, or throughout the course of a feeding bout (Goodall, 1986). Because they are only produced when food is nearby, listeners who hear these calls may be able to learn about the presence and potentially properties of this food (Slocombe and Zuberbuhler, 2005). This particular recording was made when a party of chimpanzees arrived at a tree full of new fruit.


Scream

PictureScreams typically occur in agonistic contexts and can be produced by both the victim and aggressor. They are also produced by juveniles during “tantrums”, particularly during the weaning process. Screams are thought to elicite aid in times of distress. One study even found evidence that victims may exaggerate their screams when invididuals that are higher ranking than their aggressor are nearby (Slocombe and Zuhberbuhler 2007).


Whimper


Barks (snake)

A study has found that barks given in response to snakes are acoustically different from barks produced in other contexts. This study also found that chimpanzees produced this call type 88% of the time a snake was spotted (Crockford and Boesch, 2003). I recorded these calls in captivity when chimpanzees saw a snake in the grass outside of their outdoor enclosure. Over time I learned to distinguish this call type from the others and so always knew when a snake was near by.

Huu

Jane Goodall described this call as being elicited by a state of “puzzlement, surprise, or slight anxiety” (Goodall, 1986). I recorded this particular call from a captive chimpanzee who saw her neighbors receive food instead of herself. Not much is known about this vocalization as it has never been formally studied.

Raspberry

The “raspberry” or “Bronx cheer” is a vocalization produced by captive, but not wild, chimpanzees. This vocalization is often considered to be an “attention-getting” vocalization directed towards humans. A circumstance that frequently elicits this vocalization is when a human is nearby a food item that is out of reach of a chimpanzee (Hopkins et al. 2007). This vocalization has attracted the attention of researchers because it appears to be learned and may be under voluntary control. Thus, it stands in sharp contrast to the other species-typical vocalizations of chimpanzees which are largely innate and strongly tied to the emotional state of the caller.

References

Crockford, C. and Boesch, C. Context-specific calls in wild chimpanzees, Pan troglodytes verus: analysis of barks. Animal Behaviour, 66, 115-125. 

Goodall, J. 1986. Chimpanzees of Gombe: patterns of behavior. Cambridge: Harvard University Press.

Hopkins, W.D., Taglialatela, J. and Leavens, D.A. 2007. Chimpanzees Differentially Produce Novel Vocalizations to Capture the Attention of a Human. Animal Behaviour, 73:2, 281-286.

Slocombe, K. and Zuberbuhler, K. 2005. Functionally Referential Communication in a Chimpanzee. Current Biology, 15, 1779-1784.  

Slocombe, K.E. and Zuberbuhler, K. 2007. Chimpanzees modify recruitment screams as a function of audience composition. PNAS, 104:43,  17228-17233.