The 81st Annual Meeting of the American Association of Physical Anthropologists (2012)


Do acoustics determine group-specific vocalizations? Effects of environmental acoustics on the infant vocalizations of two populations of Cebus capucinus

ANDREW R. HALLORAN1,2 and SARAH MANCZ3.

1Operations, Maderas Rainforest Conservancy, 2Anthropology, Florida Atlantic University, 3Anthropology, Miami University

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In an effort to determine what effect acoustic impedance can have on non-human primate calls, a vocal survey was performed on two groups of Cebus capucinus living in two acoustically different habitats, a lowland tropical rainforest and a highland tropical cloud forest. Among the calls surveyed was a specific infant-produced vocalization common among the species termed a “peep”. The survey revealed the infants in the high altitude habitats were using significantly greater energy (db) on lower frequencies (Hz), causing a prosodic shift in pitch. These results are concurrent with our analysis that taken as a whole, capuchins in the high altitude cloud forest are producing lower pitch calls. The results are also concurrent with our hypothesis that capuchin calls would have to conform to exponentially higher acoustic impedance caused by a high altitude environment. Such an accommodation would include utilizing lower frequency calls which are less subject to acoustic degradation than higher frequency calls. The fact that these acoustic accommodations are detected in infant calls suggests that group-specific vocalizations arise from an accommodation to the acoustic environment and may become standardized out of this need; giving rise to group-specific vocalizations.

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