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Comparing the acoustic structure of agonistic vocalizations in tolerant and intolerant macaques: a test of the social complexity hypothesis

Abstract : According to the "social complexity hypothesis", social systems characterized by complex relationships require communicative complexity. We test this hypothesis using the social diversity reported in macaques. Some macaque species display a high degree of social intolerance, with a steep gradient of dominance, which leads to clear winners and losers in conflicts. Other species are more tolerant, they exhibit more balanced relationships: subordinates can protest or counter-attack against dominant individuals, which increases the level of uncertainty – and thus complexity in the sense of Shannon’s information theory – regarding the outcomes of conflicts. We compared agonistic vocalizations in two species of macaques differing by their social style: intolerant rhesus macaques (Macaca mulatta) and tolerant Tonkean macaques (Macaca tonkeana). We recorded vocalizations emitted by adult females in 16 rhesus macaques and 13 Tonkean macaques kept in captive conditions, collecting 12 hours of focal sampling per individual. We used cluster analysis to discriminate call types based on the following acoustic features: call duration, energy quantiles features of fundamental frequencies, entropy, jitter, shimmer and harmonic to noise ratio. This revealed that Tonkean macaques emitted calls characterized by a higher number of acoustic features compared with rhesus macaques, with a number of call types two times larger in Tonkean than in rhesus macaques. Moreover, the vocalizations of Tonkean macaques showed a higher degree of overlap between call types, meaning that they used a wider number of intermediate calls. These results support the hypothesis that tolerant macaques have more complex communication signals than their more intolerant counterparts.
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Submitted on : Monday, August 20, 2018 - 9:35:28 AM
Last modification on : Wednesday, November 3, 2021 - 5:07:02 AM


  • HAL Id : hal-01858144, version 1


Nancy Rebout, Arianna de Marco, Andrea Sanna, Roberto Cozzolino, E. H. M. Sterck, et al.. Comparing the acoustic structure of agonistic vocalizations in tolerant and intolerant macaques: a test of the social complexity hypothesis. 9th European Conference on Behavioural Biology (ECBB), Liverpool John Moores University; Association for the Study of Animal Behaviour, Aug 2018, Liverpool, United Kingdom. ⟨hal-01858144⟩



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