CHIMPANZEE ARRIVAL PANT-HOOTS - DO THEY SIGNIFY FOOD OR STATUS

When adult male chimpanzees arrive at fruiting trees they commonly give long-distance pant-hoot vocalizations (arrival pant-hoots; APHs). Previous hypotheses suggested that APHs benefit listeners by informing them about large food patches and that they benefit callers by attracting allies or mates or both. We examined these ideas using data from 272 party arrivals at food sources over a 16-month period in the Kibale Forest, Uganda. To standardize for social context, we focused on arrivals at unoccupied trees. APHs at unoccupied trees were given only by parties containing at least one high-ranking adult male. In contrast to previous studies, the probability of calling was not correlated with the amount of ripe fruit in the tree, and APHs did not influence the probability of other parties arriving. Lower-ranking individuals that arrived at unoccupied trees without calling were not punished, i.e., they were not charged more often than expected. We suggest that, instead of providing information about the quality or quantity of food, APHs mark status.