Chimpanzee pant hoots are longer and more salient when males combine it with the "leaf clip" gesture

Similar to humans, non-human primates combine gestures, facial expressions, and vocalizations in various ways to communicate effectively. Chimpanzees have a well-described repertoire of both gestural and vocal signals that they use to communicate naturally in the wild, some of which show evidence for cultural variation. Researchers of the Max Planck Institute for Evolutionary Anthropology investigated one such signal, the ‘leaf clip’ gesture, which re-emerged in a wild chimpanzee group during an alpha takeover after being absent for almost two years. Importantly, the gesture was produced only by adult male chimpanzees and immediately preceded their pant hoot vocalizations and was associated with acoustic changes in those calls.