LOCOMOTION AND POSTURE OF MALAYAN SIAMANG AND IMPLICATIONS FOR HOMINOID EVOLUTION

Wild, adult siamang [Symphalangus] were observed for > 800 h in lowland dipterocarp forest in the Krau Game Reserve, Pahang, West Malaysia. Siamang use 4 patterns of locomotion: brachiation, climbing, bipedalism and leaping. The pattern of locomotion used by the siamang varies with the size of arboreal supports and with major behavioral activity. Travel is primarily by brachiation along large boughs. Locomotion during feeding is primarily climbing among small branches. In feeding siamang use suspensory postures among small supports and seated postures on large supports. Comparison of siamang locomotion and posture with that of other apes suggests that quadrumanous climbing during feeding is the basic hominoid locomotor adaptation.