Contexts and social correlates of long-distance calling by male chimpanzees

Abstract

Abstract. Chimpanzees, Pan troglodytes, live in unstable social groups, whose members associate in temporary parties of varying size and composition. Male chimpanzees utter a long-distance vocalization, the pant-hoot, that has been hypothesized to maintain spatial contact between conspecifics within and between parties. To test this hypothesis, the contexts in which calls by males were produced and the effects several social factors had on pant-hoot production were examined. Males travelled significantly more often before and after hooting than expected by chance. In addition, high-ranking males gave more pant-hoots than lower-ranking individuals, and variation in party size did not affect call production. These data are consistent with the proposed spacing function of pant-hooting, and do not support the suggestion that hooting is a simple manifestation of the high arousal levels caused by social or feeding excitement. Additional observations revealed that subjects called more frequently when alliance partners were nearby, compared with when they were absent. Males also called more when their close associates were nearby relative to situations when those associates either accompanied them or were absent. In contrast, the presence of preferred grooming partners and oestrous females within earshot did not affect the production of pant-hoots by males. These results suggest that males may pant-hoot to particular audiences within their social group, specifically to maintain contact with and to recruit allies and associates. Investigation of how chimpanzees respond to pant-hoots will be necessary to confirm this hypothesis.