Individuality and stability of isolation peeps in squirrel monkeys

Isolation peeps (IP's) made by captive squirrel monkeys (Saimiri sciureus) of both the Gothic and Roman type have been analysed by spectrographic and statistical methods designed to quantify the degree of individuality found in utterances from single individuals. Clustering analysis confirmed that in both groups of monkeys individually distinct combinations of acoustic features characterize the IP and that such unique combinations persist over periods of several years. Differences between the Gothic and Roman form of the IP were found in more aspects of acoustic structure than had previously been known. The evidence suggests that information about the identity of the vocalizer is contained in the the IP.