Wednesday, December 27, 2006


The Syntax and Meaning of Wild Gibbon Songs

An open access/free paper from PLoS ONE:

The Syntax and Meaning of Wild Gibbon Songs

By Esther Clarke, Ulrich H. Reichard, Klaus Zuberbuhler*

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.

Citation: Clarke E, Reichard UH, Zuberbühler K (2006) The Syntax and Meaning of Wild Gibbon Songs. PLoS ONE 1(1): e73. doi:10.1371/journal.pone.0000073

Continued at "The Syntax and Meaning of Wild Gibbon Songs" [Primatology]


*Klaus Zuberbuhler is author of:

The Phylogenetic Roots of Language - Evidence From Primate Communication and Cognition


The anatomy of the nonhuman primate vocal tract is not fundamentally different from the human one. Notwithstanding, nonhuman primates are remarkably unskillful at controlling vocal production and at combining basic call units into more complex strings. Instead, their vocal behavior is linked to specific psychological states, which are evoked by events in their social or physical environment. Humans are the only primates that have evolved the ability to produce elaborate and willfully controlled vocal signals, although this may have been a fairly recent invention. Despite their expressive limitations, nonhuman primates have demonstrated a surprising degree of cognitive complexity when responding to other individuals' vocalizations, suggesting that, as recipients, crucial linguistic abilities are part of primate cognition. Pivotal aspects of language comprehension, particularly the ability to process semantic content, may thus be part of our primate heritage. The strongest evidence currently comes from Old World monkeys, but recent work indicates that these capacities may also be present in our closest relatives, the chimpanzees.

And co-author (with Kate Arnold) of:

Language evolution: Semantic combinations in primate calls


Syntax sets human language apart from other natural communication systems, although its evolutionary origins are obscure. Here we show that free-ranging putty-nosed monkeys combine two vocalizations into different call sequences that are linked to specific external events, such as the presence of a predator and the imminent movement of the group. Our findings indicate that non-human primates can combine calls into higher-order sequences that have a particular meaning.


**Info on white-handed gibbons:

...The white-handed gibbon is distinguished by its musical howl. They are quiet during the day but commonly howl at sunrise and sunset. They are very vocal, making loud "whoop" sounds. Their loud resonant songs can be heard up to 1/2 mile away. Songs by far excel those of all other species because of a sound-amplifying throat sac.

Duetting is the singing between the male and female, and is dominated by the female. This helps to maintain the pair bond between the pair and to maintain the territory. Each morning upon awakening a family group of gibbons loudly announces its presence in the forest, using a territorial hooting call and menacing gestures. This call warns other gibbons to stay out of their territory (and especially away from the local fruit trees). This noisy display takes 1/2 hour or more every morning and is usually started by the adult female. The male and female have different calls.

In friendly greetings, corners of mouth are drawn back, revealing teeth, and tongue is sometimes protruding. In anger, mouth is opened and closed repeatedly, smacking lips and snapping teeth together. Snarling is interpreted as an intention of biting.

There are 9 species with 9 different territorial songs. The gibbons seem to be born knowing the songs because they are always the same, and not learned...

See "Sexual Selection and the Evolution of Brain Size in Primates"

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