Geissmann, T. 1998: Body weight in wild gibbons (Hylobatidae). In: Abstracts, XVIIth Congress of the International Primatological Society, August 10-14, 1998, abstract no. 282, University of Antananarivo, Madagascar.

Body weight in wild gibbons (Hylobatidae)

T. Geissmann

Institute of Zoology, Tierärztliche Hochschule Hannover

According to the traditional view, gibbon body weights fall into two size classes, with the siamang on one side (about 11 kg) and the gibbons on the other (about 5 kg). During a worldwide survey of museum collections, body weights of wild shot gibbons were compiled directly from the collectors' original records or from the specimens' labels. Sexual dimorphism in body weight is low and not statistically significant in most populations. Relatively large samples of body weights of wild-shot Hylobates concolor, H. leucogenys and H. hoolock are now available for the first time. In these three species, body weights average around 8 kg, 7 kg and 7 kg, respectively, and are distinctly higher than mean body weights of the various species of the lar group. The results demonstrate that H. hoolock and gibbons of the concolor group are of distinctly higher body weight than gibbons of the lar group and that a trichotomy may better describe the weight distribution in gibbons than a dichotomy. In addition, considerable differences in body weight among various populations of H. lar suggest that the isthmus of Kra represents a certain obstacle for gene exchange.