This website is meant as a brief overview of our current understanding about the incredibly loud and unique song duets of gibbons. Gibbons are wonderfully acrobatic primates (see youtube video) native to Southeast Asia. There are twelve known species of gibbons, all belonging to the family Hylobatidae (Chatterjee 2005). Due to their small size, they are frequently mistaken for monkeys, but are in fact apes. Unlike the hierarchical structure that rules mate choice and social interaction in most other apes, the social order of gibbons revolves monogamous pair-bonds. Pair-bonded gibbons are somewhat social within their neighborhood community (other pair-bonded gibbons), but spend the majority of their time with each other. They are highly territorial, and care for their offspring until they reach about 8 years of age. Gibbons who have not pair-bonded are termed 'loners', lone males or females that roam as individuals with no territory but seek a mate. The presence of loners plays an important role in understanding the gibbon duet (Raemakers & Raemaekers 1984).