Identity information in bonobo vocal communication: from sender to receiver
Abstract
Identity information is vital for highly social species as it facilitates individual
recognition and allows for differentiation between social partners in many contexts,
such as dominance hierarchies, territorial defence, mating and parent-offspring
identification, and group cohesion and coordination. For many species vocalisations
can be the most effective communication channel in complex environments and over
long-distances and are encoded with the stable features of an individual’s voice.
Associations between these individual vocal signatures and accumulated social
knowledge about conspecifics can greatly increase an animal’s fitness, as it
facilitates adaptively constructive social decisions. This thesis investigates the
encoding and decoding of identity information in the vocal communication system of
the bonobo, Pan paniscus. We firstly investigated the stability of vocal signatures
across the five most common call types in the bonobo vocal repertoire. Results
showed that while all call types have the potential to code identity information, loud
calls used during times of high arousal and for distance communication have the
strongest individual vocal signatures. Following the first study, we investigated if
social familiarity and relatedness affect the acoustic features that code individual
information in the bark call type. Overall, we found strong evidence for vocal
convergence, and specifically, that individuals who are related and familiar,
independently from one another, are more vocally similar to one another than
unrelated and unfamiliar individuals. In a final study, we tested if bonobos are
capable of using the encoded identity information to recognise past group members
that they no longer live with. Through a series playback experiments we
demonstrated that bonobos are capable of recognising familiar individuals from
vocalisations alone even after years of separation. Collectively, the results of this
thesis show that the encoding and decoding of identity information in bonobo
vocalisations is a dynamic system, subject to modification through social processes
but robust enough to allow for individual recognition over time. In conclusion, these
studies contribute to a better understanding of the vocal communication system of a
non-human primate species with a unique and complex social network.
Type
Thesis, PhD Doctor of Philosophy
Rights
Embargo Date: 2020-06-01
Embargo Reason: Thesis restricted in accordance with University regulations. Print and electronic copy restricted until 1st June 2020
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