The function of teeth chattering in male Barbary macaques (Macaca sylvanus).

Teeth chattering is seen in many primate species and has been proposed to have a range of social functions. This observational study tested specific hypotheses relating to the function of teeth chattering in a semi-free-ranging group of Barbary macaques, Macaca sylvanus. During focal watches of males, the outcome of male-male dyadic social interactions in which teeth chattering was present or absent was compared. Using these data, we tested the predictions of four hypotheses: teeth chattering functions as a signal of submission, appeasement, affiliation or reassurance. Support was found for all four hypotheses. In addition, in some contexts, an exchange of teeth chattering appeared to have a greater impact on the outcome of interactions than one male alone giving this signal. These findings suggest that teeth chattering serves an important role in coordinating the social interactions of male Barbary macaques. Copyright 2007 Wiley-Liss, Inc.