The Vocal Repertoire of Gray-Cheeked Mangabeys (Lophocebus albigena) in the Bugoma Forest Reserve, Uganda.

Vocal communication is central for regulating social interactions among primates, particularly in dense forest environments with limited visibility. The acoustic structure of vocalizations is often shaped by a species' socio-ecology. However, numerous species remain poorly documented, including the gray-cheeked mangabey (Lophocebus albigena), an arboreal primate endemic to the forests of Central and East Africa. We combined acoustic measurements with behavioral observations to provide a first quantitative and contextual description of the gray-cheeked mangabey vocal repertoire in the Bugoma Central Forest Reserve (Uganda). Using a discriminant function analysis, we report four acoustically distinct call types: chuckles, grunts, screams, and whoop-gobbles, which were also observed in different social contexts, suggesting a discrete, yet small, vocal repertoire. The two most frequently observed call types were chuckles and grunts. Chuckles were mainly produced during resting phases, and in vocal exchanges between distant individuals, suggesting they function to maintain group contact at medium or longer ranges. Grunts, in contrast, were associated with feeding and grooming, and often produced in short-distance choruses, supporting the hypothesis that they facilitate group cohesion on a smaller spatial scale. The two other call types were more rarely observed: screams were associated with agonistic interactions, while whoop-gobbles were produced more spontaneously, with no clear behavioral correlate that we could record, but may serve functions related to long-distance communication. These findings provide new insights into a little-studied species and pave the way for phylogenetic and functional comparisons with other cercopithecid primates. Nonetheless, many questions remain open and would benefit from further investigation.