Does learning affect the structure of vocalizations in chimpanzees?

We recorded 'pant-hoot' vocalizations from male chimpanzees, Pan troglodyte s, housed in two captive facilities in the U.S.A., Lion Country Safari and- North Carolina Zoological Park. Acoustic analysis revealed significant diff erences between the two groups in the temporal patterning of the calls. Bec ause the captive males within each group are from diverse origins, within-g roup similarity in pant-hoot structure could not have resulted from genetic similarity of the callers. In addition, there were no obvious differences in housing conditions that could have caused the between-group differences. Instead, the results suggest that the calls in each group converged in str ucture as a consequence of vocal learning. Within-group variation in call s tructure of the captive groups was similar to that found in a group of wild Ugandan chimpanzees (Kanyawara study group, Kibale National Park), suggest ing the presence of species-specific constraints on this call within which different populations can converge on local variants. In addition, an acous tically novel pant-hoot variant that was introduced by one male to the Lion County Safari colony spread to five other males in the same colony. This s uggests that chimpanzees may also be able to modify the frequency parameter s of their calls through learning. (C) 1999 The Association for the Study o f Animal Behaviour.