Elsevier

Animal Behaviour

Volume 122, December 2016, Pages 109-116
Animal Behaviour

Call combinations, vocal exchanges and interparty movement in wild bonobos

https://doi.org/10.1016/j.anbehav.2016.10.003Get rights and content

Highlights

  • Bonobos use call combinations during movement between separated subgroups.

  • Bonobos tend to continue calling until they receive an apparent response.

  • Caller behaviour is response dependent.

  • Call acoustics vary with context (when given spontaneously or in response).

The vocal repertoire of nonhuman primates is largely fixed. Individuals produce their species-specific vocalizations from a young age, and do not acquire new call types over their lifetime. Despite these limitations, however, monkeys and apes are able to increase their vocal flexibility in several ways, including subtle acoustic modification, call combinations, turn-taking and call persistence. Although primates have been observed to utilize these communicative features, the extent to which they integrate these abilities is not known. Here we show that certain long-distance calls produced by wild bonobos, Pan paniscus, assimilate several aspects of vocal flexibility in ways not previously documented in nonhuman primates. Communication between foraging parties exhibits context-specific call combinations relating to the movement of caller, call modifications that potentially target particular individuals, call-and-answer exchanges in which the initial caller's behaviour depends on the listener's reply, and possible persistence in call production. The selective pressure exerted by bonobos' fission–fusion social structure has likely favoured the integration of these communicative capabilities.

Section snippets

Data Collection

Bonobos form long-term, stable communities in which all members share a home range and form an exclusive reproductive unit (Kano, 1992). Within a community, individuals form temporary subgroups, or ‘parties’, that travel and forage separately from other parties. Parties are unpredictable in size (ranging from one individual to the entire community), duration (lasting from several minutes to several days) and composition (because animals do not always form a party with the same individuals).

For

High Hoots and Whistle–High Hoot Combinations

A common vocalization among bonobos is the high hoot (HH) (Fig. 1a), a loud, tonal call (de Waal, 1988) given in a variety of nonaggressive contexts, and occurring in bouts consisting of 1–27 acoustic units (Hohmann & Fruth, 1994), each with an inverted U-shaped frequency contour. High hoots are audible for at least 700 m in the forest (I. Schamberg, personal observation). They appear to be individually distinctive, and previous research suggests that they may facilitate the joining of

Discussion

Bonobos use call combinations, call exchanges and call subtypes to coordinate their movement between parties. Callers were significantly more likely to travel to a new party after producing W + HHs than after producing HHs alone. They were especially likely to move to another party if their initial vocalizations elicited an answer (i.e. was part of a vocal exchange). Individuals also modified the acoustic structure of their call combinations in a manner that could have allowed listeners to

Acknowledgments

We thank the Institut Congolais pour la Conservation de la Nature (ICCN) for permission to conduct research in D.R. Congo. We are grateful to Lys Alcayna for data collection in the field and Robyn Thiessen-Bock for drawing our attention to the W+HH combination. We also want to thank Emily Bray, Andy Gersick and Noah Synder-Mackler for their assistance, feedback and support. Research was funded by a National Science Foundation Graduate Research Fellowship (I.S.) and grants from the Leaky

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