Abstract
Spoken language is a result of the human capacity to assemble simple vocal units into more complex utterances, the basic carriers of semantic information. Not much is known about the evolutionary origins of this behaviour. The vocal abilities of non-human primates are relatively unimpressive in comparison, with gibbon songs being a rare exception. These apes assemble a repertoire of call notes into elaborate songs, which function to repel conspecific intruders, advertise pair bonds, and attract mates. We conducted a series of field experiments with white-handed gibbons at Khao Yai National Park, Thailand, which showed that this ape species uses songs also to protect themselves against predation. We compared the acoustic structure of predatory-induced songs with regular songs that were given as part of their daily routine. Predator-induced songs were identical to normal songs in the call note repertoire, but we found consistent differences in how the notes were assembled into songs. The responses of out-of-sight receivers demonstrated that these syntactic differences were meaningful to conspecifics. Our study provides the first evidence of referential signalling in a free-ranging ape species, based on a communication system that utilises combinatorial rules.
Highlights
Primates typically produce acoustic signals when detecting a predator, such as a raptor, large cat, or snake
We were interested in this initial song segment because, if gibbons conveyed any information about external events, they should do so as early as possible to benefit conspecific recipients, during predator encounters
Our field experiments revealed that white-handed gibbons of Khao Yai National Park, Thailand, were able to produce structurally different types of songs in the predator and duet contexts with the following differences
Summary
Primates typically produce acoustic signals when detecting a predator, such as a raptor, large cat, or snake. These vocalisations are termed alarm calls, which function to warn other group members and sometimes to communicate directly to the predator, for example to attract its attention or advertise perception [1]. If signallers reliably produce acoustically distinct vocalisations to different classes of predators, recipients often respond to them as if they have spotted the corresponding predator themselves, presumably because they draw inferences about ongoing external events from the calls [2]. The default assumption is that primates and other animals do not vocalise to actively inform each other, but information is transmitted as a by-product of signallers responding to evolutionarily important events
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
