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  • Print publication year: 2019
  • Online publication date: November 2019

25 - Evidence for sexual dimorphism in chimpanzee vocalizations: a comparison of male and female call production and acoustic parameters


In humans, differences in voice quality influence sexual attraction and perceived dominance, but little is known about such mechanisms in Pan. Here, we investigated the degree of sexual dimorphism in chimpanzee vocalizations. We expected the sexes to differ in mean fundamental (F0) and peak frequencies (pF) according to the source filter theory, which predicts that differences in body size affect vocal characteristics. Using data from nine chimpanzees of the South Group, we analysed call rates and measured F0, pF and durations from pant–hoots and food calls. We also tested for sex differences in bout duration and the number of food grunts per bout. Males and females had equal rates of call production for all signals except pant–hoots and buttress-drumming, with males producing these significantly more often. Additionally, contrary to predictions based on body size, female food grunts were lower in dominant frequency bands and peak frequencies while males produced longer food-call bouts with a greater number of tonal grunts. Further analyses should address whether these sex differences in acoustic parameters could play a role in female choice and male competition in chimpanzees.

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