Gibbons are the smallest of the great apes (Wilson 1975). They range in weight from about 4 kilograms to 8-15 kilograms in siamangs, the largest of the 12 (possibly 11) gibbon species (Geissmann 2001). Most species are sexually monomorphic in most respects; gibbon species have varying degrees of sexual dichromatism, however (Primate Info Net 2000).

Gibbons are known for their impressive brachiation, facilitated by extremely long arms (they have the longest arm to trunk length ratio of the primates) (Bramblett 1976). They are popular zoo exhibits because of this skilled brachiation and also because of their elaborate calls and acrobatic displays. Gibbons are also endangered animals, threatened mostly by habitat reduction, poachers, and the pet trade (AZA 1995).

The 12 species make up the genus Hylobatidae (and Symphalangus when it is considered a separate genus from Hylobatidae) are relatively similar (Geissmann 2001), particularly in terms of their social systems. All but the black-crested gibbon species are believed to live in groups made up of a monogamous, mated pair, and up to 4 subadults and infants (Gittins 1982, Wilson 1975). These groups have been traditionally been believed to be family groups of parents and offspring, but recent evidence suggests that mate-replacement leading to non-nuclear groups is prevalent (Brockleman et al. 1998). Nuclear or not, these gibbon groups actively defend classical territories which are surrounded by overlapping home ranges.

For more information on gibbon social systems, please click on the topics below.

This website was created by Karen Sweeneyfor an undergraduate Animal Behavior course at Davidson College. If you have questions or comments contact Dr. Case via email: vecase@davidson.edu