Vocal signature and social dominance hierarchy in white lipped peccary (tayassu pecari) (#2)
The white-lipped-peccary is a Neotropical mammal that lives in huge herds organized by linear hierarchy. The grunt call is one of the most frequent vocalizations in their vocal repertoire, and may play a role in the species’ social structure organization. We investigated the presence of vocal signature in grunt calls and its relationship with dominance ranking of 19 captive peccaries (9 males and 10 females). We collected 4,021 grunt calls and selected 1,849 with the best quality and least noise interference. From these we randomly chose 50 calls from each individual for DFA analysis. The acoustic parameters used were harmonic-to-noise ratio or HNR (dB), frequency interval (Hz), maximum frequency, dominant frequency (Hz) and element duration (s). The dominant male was the only animal that did not emit grunt calls. Considering all five acoustic parameters we could discriminate among the grunt calls of the 18 animals (Wilks Lambda = 0.55, P < 0.0001, N=900; cross validation: 19%, p< 0.05). The correct attribution to individuals' calls varied as a function of their dominance status (rs = -0.48, N=18, P < 0.05). We also observed that the more subordinate the individuals are, the more grunt calls they emit (rs= 0.54; n=19, P=0.008). The duration and HNH parameters provide differences between males’ and females’ grunt calls (F(2,15)= 3.21, P<0.05). Our study revealed that grunt calls provide information on animal identity, social status and sex, which is adaptive to maintain the cohesion of white-lipped peccaries that are used to living in herds comprising more than 100 individuals.