Vocal interactions between squirrel monkeys out of visual, tactile and olfactory contact

Abstract

Squirrel monkeys, when out of visual, tactile and olfactory (VTO) contact, produce calls at different frequencies of occurrence than under conditions of VTO contact. This difference is not mainly caused by an increase of calls associated with contact-distance behaviour. When squirrel monkeys communicate acoustically under restricted conditions, they attend to the same rules of communication they obey under nonrestricted conditions. They produce call rates depending on the partner's rate of vocalization. Their acoustical ‘reaction’ depends on the conspecific's preceding vocalization in both situations. Hence it follows that squirrel monkeys differentiate between conspecifics solely via acoustic cues and that they are able to ‘converse’ in ‘dialogues’ (not only in relation to contact calls) when out of sight of each other.