ABSTRACT
The New World primates are diverse in both ecology and social organization. The fact that Saimiri and Alouatta have few facial expressions and no special Pilo-erection displays might also suggest that such patterns are not more efficient than postures or movements of the limbs for short-distance communication. Olfactory signals have been studied much less thoroughly than other forms of communication in New World primates. Both Saimiri and Alouatta have comparatively few ritualized visual signals; and most of their few ritualized signals are postures and gross movements of the whole body, limbs, etc. Perhaps the structure of the Alouatta vocal apparatus is such that the production of high-pitched sounds is physically impossible. Some species and groups of species have one or more tactile signals which are peculiar to themselves alone. Some species of Platyrrhini have a few non-vocal acoustic displays.
