Terrestrial Positional Behavior of Wild Pongo pygmaeus

These observations of wild orangutan terrestrial positional behavior address prior ambiguities related to hand and foot positioning during locomotion. Maintained full extension of the hindlimb in the absence of substrate compliance indicates the form of bipedalism orangutans use in the trees translates to natural terrestrial substrates. Finally, the high proportion of observations with asymmetrical movement and posture may indicate a lateral decoupling of limbs in addition to the expected fore- and hindlimb independence of apes, suggesting orangutan positional adaptability is intrinsic regardless of substrate.