An intra-population analysis of the indris’ song dissimilarity in the light of genetic distance

Abstract

The increasing interest in the evolution of human language has led several fields of research to focus on primate vocal communication. The ‘singing primates’, which produce elaborated and complex sequences of vocalizations, are of particular interest for this topic. Indris (Indri indri) are the only singing lemurs and emit songs whose most distinctive portions are “descending phrases” consisting of 2-5 units. We examined how the structure of the indris’ phrases varied with genetic relatedness among individuals. We tested whether the acoustic structure could provide conspecifics with information about individual identity and group membership. When analyzing phrase dissimilarity and genetic distance of both sexes, we found significant results for males but not for females. We found that similarity of male song-phrases correlates with kin in both time and frequency parameters, while, for females, this information is encoded only in the frequency of a single type. Song phrases have consistent individual-specific features, but we did not find any potential for advertising group membership. We emphasize the fact that genetic and social factors may play a role in the acoustic plasticity of female indris. Altogether, these findings open a new perspective for future research on the possibility of vocal production learning in these primates.

Sexually dimorphic phrase organization in the song of the indris (Indri indri)

“…Indris ( Indri indri ; Gmelin, 1788) represent a distinctive species for studying vocal communication because of their rich repertoire (Maretti, Sorrentino, Finomana, Gamba, & Giacoma, 2010; Valente et al, 2019) and the impressive loud songs, unique among lemurs (Gamba et al, 2016; Torti et al, 2017), which can be heard at a distance up to 2 km (Pollock, 1986). Data on sound pressure levels revealed that the sound levels of the indri's song reached 110 dB (estimated at 0.50 m; Torti, pers.…”

“…Females may use songs for mate attraction (Rogers et al, 2007), and they may even show a more elaborated song repertoire (Australian magpies; Gymnorhina tibice Brown & Farabaugh, 1991). Like Eastern whip birds and Australian magpies, indris are monogamous (Bonadonna et al, 2019; Torti et al, 2017), form groups that occupy nonoverlapping areas in the forest (Bonadonna et al, 2017), and use the songs to inform neighboring groups about the occupation of a territory and to actively defend resources during group encounters (Torti et al, 2013). Thus, we hypothesized that the female contribution to the song would be structurally different from that of males.…”

Interactive rhythms across species: the evolutionary biology of animal chorusing and turn‐taking

“…Main focus on behavioral and neurocognitive mechanisms 11 Focus on different explanatory levels, from genetics 10,53 to neurobiology and behavior 27…”

“…This historical focus on individual language capacities, partly due to a generativist tradition in language sciences, is rapidly changing . Unanswered questions regarding how individual communicative rhythms are shaped by group interactions and modulated by social behavior are starting to be addressed . The study of conversation and turn‐taking is taking center stage …”

“…5,6 Unanswered questions regarding how individual communicative rhythms are shaped by group interactions and modulated by social behavior are starting to be addressed. [7][8][9][10] The study of conversation and turn-taking is taking center stage. [11][12][13] To understand the origins and evolution of language, the comparative approach targets analogous or homologous language-relevant traits in nonhuman animals.…”