Quantitative analysis of the vocal repertoire of squirrel monkeys (Saimiri sciureus)

During experiments concerning the communication of squirrel monkeys, it proved to be necessary to construct an automatic apparatus for the identification of individual calls (MAURUS et al. 1970). The aim of this paper was to furnish the necessary data to achieve this (frequency, duration and the relationship of the intensity between the fundamental frequency and the overtones). 6120 calls from 19 animals were analysed and were subdivided into 52 call types. It was thereby shown: 1. That the vocal repertoire consists not of the discrete call types assumed up to now, but of graded ones; 2. that the animals could not be differentiated as individuals on the basis of the particular parameter of their calls. The distribution into 52 call types is not necessarily biologically significant. A final statement about the distribution of call types can be made only after the signal value of each call type has been determined.