Vocalization of red- and grey-shanked douc langurs (Pygathrix nemaeus and P. cinerea)

The vocal repertoires of red- and grey-shanked douc langurs (Pygathrix nemaeus and P. cinerea) have never been described before. Information derived from the recordings of the captive groups of the Endangered Primate Rescue Center, Cuc Phuong National Park, Vietnam, was used for a first quantitative description of these species’ calls based on the calculation of pairwise dissimilarity indexes and cluster analysis. Distinctive features were found across the 8 vocal types identified for each species. Some of the clusters are feasibly representing call variants belonging to an acoustic continuum, but others clearly represent distinct types. The potential changes occurring due to sex- and age-dependent characteristics were not investigated in the present study.