INTRAGROUP VOCAL BEHAVIOR IN WILD GOLDEN LION TAMARINS, LEONTOPITHECUS-ROSALIA - HONEST COMMUNICATION OF INDIVIDUAL ACTIVITY

We report the first field study of the intra-group vocal behaviour of golden lion tamarins (Leontopithecus rosalia). We present the contexts in which the five predominant intra-group vocalizations (cluck, whine, wah-wah, tsick, and trill) were emitted, including the behavioural responses elicited from other group members, for 25 adult and subadult golden lion tamarins in five wild groups. No age (subadult versus adult), sex, age of nearest neighbour, and few group differences in call usage were identified. Each intra-group vocalization was associated with a specific ecological context; few vocalizations were produced during dyadic social interactions. Clucks predominated during foraging. Clucks were also relatively more common when the group was travelling, but the focal tamarin was stationary (not locomoting). Whines were more likely when the animal was in a travelling group, stationary, not foraging or locomoting, and when the nearest neighbour was further away than five m. Trills were almost exclusively emitted when a tamarin was leaping, and were a strong predictor of foraging upon landing. No change in the mean distance to the nearest neighbour was detected subsequent to the production of a cluck, whine or trill, although juveniles immediately approached to obtain food items when tsick calls were uttered. Wah-wahs were more likely when the caller was on the group periphery and may function in the initiation and leading of group movement; a stationary group usually moved in the trajectory predicted by the wah-wahing tamarin's location relative to the group center. These findings suggest that the intra-group vocalizations of this small arboreal primate provide honest information regarding numerous aspects of the caller's immediate location, activity and intent. Directly and indirectly these vocalizations may function to facilitate group cohesion and the coordination of group movement by enhancing cooperation among group members.