Food -associated calls in white -faced capuchin monkeys (Cebus capucinus): Different functions from the perspective of the signaler and the recipient

Food-associated calls are widespread in mammalian and avian species. Researchers have based hypotheses about the function of these calls on the responses of call recipients. It is assumed that these calls have evolved to attract others to a food source because call recipients often approach a caller. However, few researchers have investigated the possibility that food-associated calls serve a different function for the signaler than attracting others to a food source. Food-associated calls in white-faced capuchin monkeys were studied to explore the function of these calls independently from the perspective of the signaler and the perspective of the recipient. Naturalistic observations and food placement experiments were conducted to determine the factors that influence the production of food-associated calls. Results showed that the factors that influenced call production were inconsistent with an information-sharing function. Instead, for signalers, food-associated calls appeared to function to announce food ownership, thereby decreasing aggression from other individuals. Playback experiments were performed to investigate whether food-associated calls, although announcing food ownership nonetheless provide information to listeners about the presence of food. In playback experiments, individuals responded to calls in a manner consistent with how they responded to naturally occurring calls. Subjects looked toward the speaker for significantly longer durations after they heard a food-associated call than after they heard a control vocalization. Individuals also moved in the direction of the speaker after hearing a food-associated call in 9 of the 28 trials, whereas they did not approach the speaker in the control trials. Listeners, therefore, appeared to be able to extract information from the calls about the presence of food. Results of this study of food-associated calls in white-faced capuchin monkeys suggest that calls serve a different function for signalers than for recipients. Signalers appeared to call to announce food ownership. However, because listeners have come to associate the call with the presence of food, they responded to the calls as if they had been informed about food. These results suggest that is important to consider the possibility that animal vocalizations may serve a primary function for the signaler, and a secondary, coincidental function for recipients