FOOD-ASSOCIATED CALLS IN RHESUS MACAQUES (MACACA-MULATTA) .1. SOCIOECOLOGICAL FACTORS

Upon discovering food, free-living rhesus macaques (Macaca mulatta) on the island of Cayo Santiago, Puerto Rico, produce a complex of vocal signals consisting of five acoustically distinguishable calls. This re port examines the socioecological factors eliciting call production an d the information potentially conveyed to others. The primary contexts for three vocalizations (''warbles,'' ''harmonic arches,'' and ''chir ps'') are encounters with rare and highly preferred foods (e.g., cocon ut). Two other vocalizations (''coos'' and ''grunts'') are produced bo th in food (primarily provisioned chow) and in nonfood contexts, such as during mother-infant separation and grooming interactions. Grunts g iven upon encountering food are acoustically distinct from those given in nonfood contexts. In contrast, coos associated with food are stati stically indistinguishable from coos given in other contexts. When con specifics hear these food-associated calls, they typically approach th e caller. Coos are less likely to lead to approach than other food-ass ociated calls. Results from all-day follows on adult males and adult f emales reveal that changes in hunger level influence call rate but not call type; the different call types are produced throughout the day. We infer that the structure of food-associated calls provides informat ion about the quality of the food discovered, whereas call rate convey s information about the relative hunger level of the caller. In this p opulation, adult males give fewer food-associated calls than adult fem ales. In addition, females within large matrilines call more than fema les within smaller matrilines, and males who are resident in a group a re more vocal than peripheral males.