Temporal and structural organization of nonhuman primate call sequences
Studies of vocal production including the neurobiological foundation of vocal control have shown that nonhuman primates have only little voluntary control over the acoustic structure of their calls. Thus they are not able to extend their communication capacity by inventing new call variants. It has been suggested that nonhuman primates could increase the information capacity of their vocalizations by combining different call types or elements. To answer this question it is necessary to develop quantitative methods to describe the temporal and combinatorial structure of such sequences. In this project, we investigated whether a non-parametric statistical approach recently developed by Flocencia Noriega on pilot whale vocalizations can be applied to nonhuman primate call sequences, which mainly consists of graded vocalizations. As a first result we successfully applied this non-parametric statistical approach on the alarm call sequences of green monkeys finding different temporal and combinatorial patterns in relation to sex and alarm call context. A verification of the approach with a second dataset of graded vocalizations supported the view that this approach is generally applicable to graded vocal repertoires.