Primate Vocalisations: Structural and Functional Approaches To Understanding

Abstract

Research on primate vocal behaviour has shown it to be varied, complex and intricate; selected developments of particular interest are reviewed, and the methodological advances which allowed them are described. Primate repertoires are extensively graded, but this continuous variation may be perceived discretely by the animals: some species at least show categorical perception of their calls, which means that the lists of in the primate literature are largely misleading. In addition, some species show complex patterning which has yet to be properly understood. A rudimentary form of syntax and simple compounding of call meanings has been shown. It is now known that calls can convey population dialect and individual identity, and in certain cases can refer to classes of objects in a fashion analogous to that of words in speech. Calls normally give information on the caller's location, but may be specialised to avoid doing so or to do so better, where these are advantageous. Specialisation is also shown in perception, with neurally lateralised apparatus for processing of conspecifics' calls. Long distance propagation of certain calls is enhanced both by signal form and time and manner of delivery. Such calls are well suited for experimental study, and are now among the best understood. Function turns out to be more labile than form in evolution of vocalisations, with homologous calls serving different functions in close relatives; in addition, calls apparently identical in form may mediate several unrelated functions in a single species. Long-range calls are employed especially to coordinate movements where groups are dispersed in areas of low visibility, and in various different ways as components of intergroup spacing systems.