Limits...
Context-specific close-range "hoo" calls in wild gibbons (Hylobates lar).

Clarke E, Reichard UH, Zuberbühler K - BMC Evol. Biol. (2015)

Bottom Line: Our study provides evidence that lar gibbons are able to generate significant, context-dependent acoustic variation within their main social call, which potentially allows recipients to make inferences about the external events experienced by the caller.Communicating about different events by producing subtle acoustic variation within some call types appears to be a general feature of primate communication, which can increase the expressive power of vocal signals within the constraints of limited vocal tract flexibility that is typical for all non-human primates.In this sense, this study is of direct relevance for the on-going debate about the nature and origins of vocally-based referential communication and the evolution of human speech.

View Article: PubMed Central - PubMed

Affiliation: Evolutionary Anthropology Research Group, Dawson Building, Durham University, Durham, DH1 3LE, UK. e.a.clarke@durham.ac.uk.

ABSTRACT

Background: Close range calls are produced by many animals during intra-specific interactions, such as during home range defence, playing, begging for food, and directing others. In this study, we investigated the most common close range vocalisation of lar gibbons (Hylobates lar), the 'hoo' call. Gibbons and siamangs (family Hylobatidae) are known for their conspicuous and elaborate songs, while quieter, close range vocalisations have received almost no empirical attention, perhaps due to the difficult observation conditions in their natural forest habitats.

Results: We found that 'hoo' calls were emitted by both sexes in a variety of contexts, including feeding, separation from group members, encountering predators, interacting with neighbours, or as part of duet songs by the mated pair. Acoustic analyses revealed that 'hoo' calls varied in a number of spectral parameters as a function of the different contexts. Males' and females' 'hoo' calls showed similar variation in these context-specific parameter differences, although there were also consistent sex differences in frequency across contexts.

Conclusions: Our study provides evidence that lar gibbons are able to generate significant, context-dependent acoustic variation within their main social call, which potentially allows recipients to make inferences about the external events experienced by the caller. Communicating about different events by producing subtle acoustic variation within some call types appears to be a general feature of primate communication, which can increase the expressive power of vocal signals within the constraints of limited vocal tract flexibility that is typical for all non-human primates. In this sense, this study is of direct relevance for the on-going debate about the nature and origins of vocally-based referential communication and the evolution of human speech.

Show MeSH

Related in: MedlinePlus

a-f. Box plots of the mean values for each measured acoustic parameter (not accounting for individual identity). Panel a) duration, b) intercall interval, c) peak frequency, d) low frequency, e) delta frequency, f) intensity. Error bars represent 95% CI. Different letters above box plots indicate significant differences between contexts. Where sex differences were found plots are split into two panels: F = female, M = male.
© Copyright Policy - open-access
Related In: Results  -  Collection

License 1 - License 2
getmorefigures.php?uid=PMC4389582&req=5

Fig1: a-f. Box plots of the mean values for each measured acoustic parameter (not accounting for individual identity). Panel a) duration, b) intercall interval, c) peak frequency, d) low frequency, e) delta frequency, f) intensity. Error bars represent 95% CI. Different letters above box plots indicate significant differences between contexts. Where sex differences were found plots are split into two panels: F = female, M = male.

Mentions: Gibbons lack an obvious sexual dimorphism in body size, possibly due to their sometimes monogamous grouping structure [43]. While Khao Yai gibbons show stable polyandrous groupings as well as monogamous ones [44], we do not predict any differences in vocal behaviour. We found that the average peak frequency of hoos was 521.9Hz ± 3.79SE, (n = 462) with an average duration of 0.08 s ±0.002SE (n = 462). Surprisingly, however, we also found that male hoos had significantly higher peak frequencies (F0) and low frequencies than female hoos (Table 2, Figure 1). No sex differences were found in other acoustic parameters.Table 3


Context-specific close-range "hoo" calls in wild gibbons (Hylobates lar).

Clarke E, Reichard UH, Zuberbühler K - BMC Evol. Biol. (2015)

a-f. Box plots of the mean values for each measured acoustic parameter (not accounting for individual identity). Panel a) duration, b) intercall interval, c) peak frequency, d) low frequency, e) delta frequency, f) intensity. Error bars represent 95% CI. Different letters above box plots indicate significant differences between contexts. Where sex differences were found plots are split into two panels: F = female, M = male.
© Copyright Policy - open-access
Related In: Results  -  Collection

License 1 - License 2
Show All Figures
getmorefigures.php?uid=PMC4389582&req=5

Fig1: a-f. Box plots of the mean values for each measured acoustic parameter (not accounting for individual identity). Panel a) duration, b) intercall interval, c) peak frequency, d) low frequency, e) delta frequency, f) intensity. Error bars represent 95% CI. Different letters above box plots indicate significant differences between contexts. Where sex differences were found plots are split into two panels: F = female, M = male.
Mentions: Gibbons lack an obvious sexual dimorphism in body size, possibly due to their sometimes monogamous grouping structure [43]. While Khao Yai gibbons show stable polyandrous groupings as well as monogamous ones [44], we do not predict any differences in vocal behaviour. We found that the average peak frequency of hoos was 521.9Hz ± 3.79SE, (n = 462) with an average duration of 0.08 s ±0.002SE (n = 462). Surprisingly, however, we also found that male hoos had significantly higher peak frequencies (F0) and low frequencies than female hoos (Table 2, Figure 1). No sex differences were found in other acoustic parameters.Table 3

Bottom Line: Our study provides evidence that lar gibbons are able to generate significant, context-dependent acoustic variation within their main social call, which potentially allows recipients to make inferences about the external events experienced by the caller.Communicating about different events by producing subtle acoustic variation within some call types appears to be a general feature of primate communication, which can increase the expressive power of vocal signals within the constraints of limited vocal tract flexibility that is typical for all non-human primates.In this sense, this study is of direct relevance for the on-going debate about the nature and origins of vocally-based referential communication and the evolution of human speech.

View Article: PubMed Central - PubMed

Affiliation: Evolutionary Anthropology Research Group, Dawson Building, Durham University, Durham, DH1 3LE, UK. e.a.clarke@durham.ac.uk.

ABSTRACT

Background: Close range calls are produced by many animals during intra-specific interactions, such as during home range defence, playing, begging for food, and directing others. In this study, we investigated the most common close range vocalisation of lar gibbons (Hylobates lar), the 'hoo' call. Gibbons and siamangs (family Hylobatidae) are known for their conspicuous and elaborate songs, while quieter, close range vocalisations have received almost no empirical attention, perhaps due to the difficult observation conditions in their natural forest habitats.

Results: We found that 'hoo' calls were emitted by both sexes in a variety of contexts, including feeding, separation from group members, encountering predators, interacting with neighbours, or as part of duet songs by the mated pair. Acoustic analyses revealed that 'hoo' calls varied in a number of spectral parameters as a function of the different contexts. Males' and females' 'hoo' calls showed similar variation in these context-specific parameter differences, although there were also consistent sex differences in frequency across contexts.

Conclusions: Our study provides evidence that lar gibbons are able to generate significant, context-dependent acoustic variation within their main social call, which potentially allows recipients to make inferences about the external events experienced by the caller. Communicating about different events by producing subtle acoustic variation within some call types appears to be a general feature of primate communication, which can increase the expressive power of vocal signals within the constraints of limited vocal tract flexibility that is typical for all non-human primates. In this sense, this study is of direct relevance for the on-going debate about the nature and origins of vocally-based referential communication and the evolution of human speech.

Show MeSH
Related in: MedlinePlus