Acoustical communication among free-ranging common indian langurs (Presbytis entellus) in two different habitats of North India

Acoustical signals of free-ranging Presbytis entellus were analyzed with the aid of sonagrams. Tape-recordings were from two ecologically-different habitats in North India, the Kumaon Hills on the southern slope of the Himalayas and the plains habitat of Rajasthan. The acoustical quality and the spectrographic structure of the signals are described and their communicative functions within the social context discussed. We found significant differences in the acoustical repertoire of the langurs of the two habitats both in the tone quality and the spectrographical structure of single signals serving the same functions in both regions and in functional deviations of identically or similarly structured vocalizations. Some of these differences appear to be phylogenetic adaptations to the different environmental conditions of the habitats or to be related to special types of social organization in the two separate langur populations.