Dusk calling in barbary macaques (Macaca sylvanus): Demand for social shelter.

Barbary macaques (Macaca sylvanus) show an increase in vocal activity at dusk. This investigation showed that these vocalizations were mainly produced by juveniles from six to 18 months of age, during their attempts to achieve body contact with their mothers, thereby building up a sleeping cluster. The "dusk calling" consisted of protracted sequences of variable vocal patterns which always ceased when the juvenile joined its preferred sleeping cluster. The length of the sequences corresponded to the time it took the juvenile to be accepted into a sleeping cluster. One-year-old juveniles exhibited the highest vocal activity. The similarity of the results obtained in two outdoor enclosures in France and of those in the field (Morocco) indicated that dusk calling is common to this species, and not a behavior unique to captive animals. © Wiley-Liss, Inc.