Chimpanzee food-associated calls display low referential potential in a wild population

Abstract

Studies of non-human primate vocal communication commonly focus on “functionally referential signals,” which are thought to function like human words, informing receivers about stimuli in the external environment. Captive studies of the food-associated “rough-grunt” of chimpanzees (Pan troglodytes) report that their acoustic structure varies according to food quality and even type, suggesting the existence of functionally referential communication in humans' evolutionary cousins. Nevertheless, studies of wild chimpanzees have produced mixed evidence that rough-grunts function referentially in natural contexts. The current study builds upon these findings by conducting an acoustic analysis of rough-grunts produced by wild chimpanzees at Gombe National Park, Tanzania, examining acoustic variation in call duration and peak frequency both within and between feeding bouts. We found that peak frequency, but not duration, displayed a bimodal distribution, supporting the view that rough-grunts include at least tw...