Intergroup and intragroup antiphonal songs in wild male Mueller’s gibbons ( Hylobates muelleri )

Mueller’s gibbons (Hylobates muelleri) sing both sex-specific and duet songs. These songs are thought to be involved in territory maintenance, as well as the maintenance of pair or family bonds. However, few observational studies have examined how gibbons interact with their neighbors through song in the wild. We have been conducting field observations of wild gibbon groups in northeast Borneo since 2001. In the Borneo Rainforest Lodge (BRL) and Danum Valley Field Center (DVFC) at the Danum Valley Conservation Area (DVCA), we observed seven episodes of alternating songs between males. Here, we describe the process of song exchange between males. During male interactions, song bouts rarely overlapped and were alternately emitted. Several studies have reported antiphonal vocalizations in New World and Old World primate species, but rarely in apes. Our observations of antiphonal songs in gibbons indicate that gibbons not only unilaterally advertise information, but also interactively communicate with neighbors and family members through songs. Since gibbons are phylogenetically similar to humans, and turn-taking has an important role in human conversation, our research on gibbon communication may provide insight into the evolution of human language.