Terrestrial locomotion and back anatomy in vervets (Cercopithecus aethiops) and patas monkeys (Erythrocebus patas).

This comparative study addressed the problem of relationships between locomotor behavior and back anatomy in the cursorial monkeys, Cercopithecus aethiops and Erythrocebus patas. Analysis of cine-film revealed that patas and vervet monkeys differed significantly in the degree to which they used their backs to increase stride length during galloping. C. aethiops showed increased ranges of sagittal back motion as galloping speed increased almost fivefold; E. patas failed to show significant increases in amplitudes of sagittal back motion despite a five-to-sixfold increase in galloping speed. Comparison of epaxial anatomies demonstrated conservative morphologic features which could not be used to explain interspecific differences in sagittal movement patterns of the back. However, when compared to patas monkeys, vervets possessed thicker intervertebral discs, relative to vertebral bone, and reduced dorsoventral diameters of their theracic cages. These anatomic differences were explained on the basis of theoretical bio-mechanics as being necessary structural prerequisites for enhancing sagittal back mobility. The present analysis of locomotor behavior involving the back and epaxial morphologies was integrated with observations of interspecific differences in limb anatomies and comparative anatomic studies of other mammalian species to develop a general description of strategies used by patas and vervet monkeys to increase stride length during galloping.