Isochronous singing in 3 crested gibbon species(Nomascus spp.)

The search for common characteristics between the musical abilities of humans and other animal species is still taking its frst steps.One of the most promising aspects from a comparative point of view is the analysis of rhythmic components,which are crucial features of human communicative performance but also well-identifable patterns in the vocal displays of other species.Therefore,the study of rhythm is becoming essential to understand the mechanisms of singing behavior and the evolution of human communication.Recent fndings provided evidence that particular rhythmic structures occur in human music and some singing animal species,such as birds and rock hyraxes,but only 2 species of nonhuman primates have been investigated so far(Indri indri and Hylobates lar).Therefore,our study aims to consistently broaden the list of species studied regarding the presence of rhythmic categories.We investigated the temporal organization in the singing of 3 species of crested gibbons(Nomascus gabriellae,Nomascus leucogenys,and Nomascus siki)and found that the most prominent rhythmic category was isochrony.Moreover,we found slight variation in songs’tempo among species,with N.gabriellae and N.siki singing with a temporal pattern involving a gradually increasing tempo(a musical accelerando),and N.leucogenys with a more regular pattern.Here,we show how the prominence of a peak at the isochrony establishes itself as a shared characteristic in the small apes considered so far.

Modeling individual vocal differences in group-living lemurs using vocal tract morphology

Vocal individuality is widespread in social animals. Individual variation in vocalizations is a prereq- uisite for discriminating among conspecifics and may have facilitated the evolution of large complex societies. Ring-tailed lemurs Lemur catta live in relatively large social groups, have con- spicuous vocal repertoires, and their species-specific utterances can be interpreted in light of source-filter theory of vocal production. Indeed, their utterances allow individual discrimination and even recognition thanks to the resonance frequencies of the vocal tract. The purpose of this study is to determine which distinctive vocal features can be derived from the morphology of the upper vocal tract. To accomplish this, we built computational models derived from anatomical measurements collected on lemur cadavers and compared the results with the spectrographic out- put of vocalizations recorded from ex situ live individuals. Our results demonstrate that the mor- phological variation of the ring-tailed lemur vocal tract explains individual distinctiveness of their species-specific utterances. We also provide further evidence that vocal tract modeling is a power- ful tool for studying the vocal output of non-human primates.

Animal vocal communication： function, structures, and production mechanisms

Introduction Understanding the processes involved in how and why animals com- municate has long been fascinating to scientists （Darwin 1871 ）. This endeavor plays a key role in the pursuit of reaching a better compre- hension both of the rules involved in organizing the animal societies around us （Freeberg et al. 2012） and of the evolutionary bases under- lying our own vocal communication system： human language （Fitch 2010）. Moreover, in recent years, the type and function of informa- tion conveyed by animal vocalizations have also attracted research interest in the field of ecology （see Sueur and Farina 2015）.