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Chest beats as an honest signal of body size in male mountain gorillas (Gorilla beringei beringei) - PubMed

  • ️Fri Jan 01 2021

Chest beats as an honest signal of body size in male mountain gorillas (Gorilla beringei beringei)

Edward Wright et al. Sci Rep. 2021.

Abstract

Acoustic signals that reliably indicate body size, which usually determines competitive ability, are of particular interest for understanding how animals assess rivals and choose mates. Whereas body size tends to be negatively associated with formant dispersion in animal vocalizations, non-vocal signals have received little attention. Among the most emblematic sounds in the animal kingdom is the chest beat of gorillas, a non-vocal signal that is thought to be important in intra and inter-sexual competition, yet it is unclear whether it reliably indicates body size. We examined the relationship among body size (back breadth), peak frequency, and three temporal characteristics of the chest beat: duration, number of beats and beat rate from sound recordings of wild adult male mountain gorillas. Using linear mixed models, we found that larger males had significantly lower peak frequencies than smaller ones, but we found no consistent relationship between body size and the temporal characteristics measured. Taken together with earlier findings of positive correlations among male body size, dominance rank and reproductive success, we conclude that the gorilla chest beat is an honest signal of competitive ability. These results emphasize the potential of non-vocal signals to convey important information in mammal communication.

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Conflict of interest statement

The authors declare no competing interests.

Figures

Figure 1
Figure 1

Mountain gorilla silverback PTO chest beating.

Figure 2
Figure 2

Relationship between body size (back breadth) and peak frequency of chest beats. The area of the circles represents sample size (N = 36). The dashed line is the fitted model after controlling for age and the shaded area is its 95% confidence intervals.

Figure 3
Figure 3

Spectrogram of a chest beat highlighting the response variables used in the analysis.

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