Playbacks of Food-associated Calls Attract Chimpanzees Towards Known Food Patches in a Captive Setting

Abstract

Food-associated calls have attracted much research attention due to their potential to refer to discovered food in a word-like manner. Nevertheless, their effect on receiver behavior remains unclear for many species. While some studies suggest that food-associated calls attract other foragers, other studies indicate that they repel others. We conducted playback studies to differentiate between these two hypotheses for the function of the chimpanzee (Pan troglodytes) food-associated rough grunt. We tested how acoustic playbacks of rough grunts (or control calls) from one of two known, identical food patches affected receivers foraging decisions in a captive setting. We found that participants were more likely than chance to first investigate the patch from which rough-grunts, but not control calls, were broadcast. However, neither condition increased the likelihood that participants fed first from a given patch. Our results support the hypothesis that rough-grunts attract receivers. However, since receivers were already aware of the presence of food, our results question whether rough-grunts attract by conveying information about discovered food, or rather, the signalers motivational state.