International Journal of Primatology, VoL 12, No. 2, 1991 Positional Behavior in the Hominoidea Kevin D. Hunt l Received June 11, 1990;revised September 17, 1990 Quantitative studies on the positional behavior of members of the Hominoidea are compared in order (1) to identify consistencies across the superfamily, (2) to contrast ape positional behavior with that of Old World monkeys (forest-living Papio anubis were chosen for study to reduce body size effects), and (3) to identify distinctive behaviors in each of the ape taxa. Differences in the way behaviors were sampled in the various studies neces- sitated considering posture and locomotion separately. Unimanual arm-hang- ing and vertical climbing were the most distinctive shared postural and locomotor modes among the apes (the gorilla excepted), constituting >_5.0% and >_4.9% of all behavior in each species. Arm-hanging and brachiation (sensu stricto) frequencies were the highest by far in hylobatids. Hand-foot hanging, bipedal posture, and clambering, an orthograde suspensory locomo- tion assisted by the hindlimbs, were more common in orangutans than in any other hominoid. Sitting and walking were observed in the highest fre- quencies in the African apes but were no more common than in the baboon. Relatively high frequencies of brachiation (sensu stricto) were reported for all apes except chimpanzees and gorillas. Brachiation and arm-hanging were kinematically different in apes and baboons, involving complete humeral ab- duction only in the former, whereas vertical "climbing appeared to be kine- maticaUy similar in apes and baboons. It is concluded that the morphological specializations of the apes may be adaptations to (1) the unique physical demands of arm-hanging and (2) less kinematicaUy distinct, but still quanti- tatively significant, frequencies of vertical climbing. KEY WORDS- locomotion; posture; brachiation; climbing; arm-hanging. 1Peabody Museum, Harvard University, Cambridge, Massachusetts 02138. 95 0164-0291/91/0400-0095506.50/0 9 1991 Plenum Publishing Corporation