Lost in Transmission: Contextual Variation in Chimpanzee Pant Hoots and its Implications for Referential Communication presented at the Animal Behaviour Society 45th Annual Meeting in Snowbird Resort, UT, August 16-20, 2008

Abstract

There have been several previous studies of the loud, long-distance calls of chimpanzees, termed ‘pant hoots’. Some have explored the possibility that there are acoustically distinct subtypes of pant hoots that communicate to distant listeners different information about the caller’s behaviour, or ecological and social circumstances. However, research aimed at assessing the degree to which pant hoots constitute ‘referential’ animal signals have thus far been either inconclusive or conflicting. To help resolve these issues, we undertook research on pant hoots produced by wild chimpanzees (Pan troglodytes schwienfurthii) living in the Budongo Forest, Uganda. In this paper, we report the results of acoustic analysis of 201 pant hoot series produced by seven adult males. Our results show that individual variation exceeds those differences observed between production contexts. In addition, what contextual variation we did observe occurred in acoustic features that are expected to vary with arousal and/or as by-products of physical activities associated with call production. We propose that pant hoots function primarily to transmit information about caller identity to dispersed group members, and that receivers might infer the situational context of the caller via associated auditory cues, such as caller location, direction of travel and social circumstance, that are independent of call structure.