Structure and contexts in the long distance calls of Alouatta clamitans and Alouatta belzebul.

Abstract

The structure of the long range calls of howler monkeys, primates of the genus Alouatta, is scarcely understood in relation to the functions they assume. Records of Alouatta clamitans and Alouatta belzebul long distance calls were obtained at different Brazilian sites. The long distance calls of both species are low‐frequency, harsh, loud sounds, uttered in sequences that may last several minutes. There is wide gradation both within and between call categories. The structure of roars and barks seems to serve different roles: barks function as graded signals of alarm, roars as resource holding potential signals used in resource defense. Observations in A. clamitans give support to such hypotheses. Roar use and structure have the most marked differences between these species. A dawn chorus of roaring was observed only for A. belzebul, which probably has a more spontaneous emission of roars, while A. clamitans use roars mainly in intergroup encounters. The structural divergence between the long range calls of these species may reflect species–typical adaptations. The presence of both brief and continuous roars in both species, but not in the most basal Alouatta palliata can bring cues to loud calling evolution in howlers. [Work supported by CNPq, FAPESP, IF/SP, FURB, CEPESBI, IBAMA/PB, and Fazenda Pacatuba.]