Geissmann, T. (1995). Gibbon systematics and species identification. International Zoo News 42: 467-501.

Gibbon systematics and species identification

T. Geissmann
Anthropological Institute, University Zürich-Irchel, Switzerland

Abstract: A study of wild and captive gibbons and museum specimens, and a survey of the literature suggests that gibbons (genus Hylobates) include at least 11, possibly 12 species, which form 4 distinct groups (subgenera Hylobates, Bunopithecus, Nomascus, and Symphalangus): These are the 44-chromosome gibbons (including the Hylobates lar group and H. klossii: 5 species); the hoolock (H. hoolock, 1 species); the H. concolor group (3, possibly 4 species); and the siamang (H. syndactylus, 1 species). A key for the identification of adult gibbons based on visual characteristics is presented, together with colour photographs and distribution maps of all recognised species (11). In addition, diagnostic vocal characteristics of all species are described and illustrated with sonagrams.