Kanyawara chimpanzees are the focus of a new study on vocal behavior by Pawel Fedurek and colleagues. Chimpanzees live in flexible fission-fusion societies, meaning that within a community they form temporary subgroups that frequently change in size and composition. Animals living in such fluid societies often use long-distance calls to communicate with other subgroups. Chimpanzees are no exception: research on chimpanzee vocal behaviour at Kanyawara suggests that male pant hoots (long-distance calls commonly produced by these apes) play a pivotal role in locating and facilitating reunions with other community members, especially males. For example, study males were more likely to reunite with other males on days when they pant hooted more, and they stopped calling once a reunion had occurred. These findings support the view that pant hooting is an important tool in mediating grouping decisions in chimpanzees.
However, the study also shows that males were more likely to call on days when a female in estrus was present in their subgroup, and when they fed on high-quality food. In addition, high-ranking males tended to pant hoot more than low-ranking ones. Therefore, pant hooting might also signal social status or social bonds when males compete for valuable resources. The authors conclude that while facilitating reunions with other males might be an especially important function of male pant hooting, this behaviour fulfills several social functions.