The pant-hoot is a loud, structurally complex vocalization of chimpanzees. The call is generally divided into four distinct, successive phases: introduction, build-up, climax and let-down. This introductory phase begins with soft, breathy, low-frequency 'hoo's' that transition into the build-up phase; a series of increasingly rapid, low-frequency in-and-out pants. Following the build-up phase, the call quickly builds into the climax, consisting of loud, high-frequency screams that eventually slow into the let-down phase, similar in structure to the build-up, but with decreasing amplitude and pace until the call is complete. Both male and female chimpanzees produce these unique vocalizations, with high-ranking adult males predominantly and more frequently emitting the pant-hoot. The pant-hoot is most often produced jointly with other males, in a complementary behaviour known as chorusing, as opposed to producing the calls individually. These loud, long-distance vocalizations are produced for numerous purposes in a variety of different circumstances and situations. Pant-hoot chorusing can be used to aid in the formation of social groups or parties amongst male chimpanzees, and used to display the dominance and strength of their party to conspecifics. Pant-hoots are also produced upon the arrival of fruit trees to indicate the location of abundant resources and when joining and greeting other members of their social group. Calls are produced to indicate the spatial location of the individuals in a party, facilitating the maintenance and unity of the social group by providing a means of communication between members while travelling, often listening to the distant calls made by other chimpanzees and responding to them. Also, pant-hoots are used to identify and distinguish between members of a social group, as each individual upholds some variation in their specific calls. Additionally, the level of pant-hooting in chimps vary based upon their individual dominance rank within a party. There are also levels of variation observed within the structure and expression of pant-hoot calls within this range of circumstances, which serve to separate populations, social parties and individuals from one another, allowing coherence between the members in all situations, as well as the establishment of individual identities among each chimp. Social bonding (affiliation) Pant-hoot chorusing in chimpanzees is a facilitative method of social bonding between males in a population and can be indicative of the level of affiliation between members in a party. A social affiliation between male chimpanzees can be recognized by observable behaviours such as reciprocal grooming, non-vocal displays and the