| Abstract: | Over 150 sequences of terrestrial movement were timed and measured in the toque macaque, the gray langur, and the purple-faced langur to determine the relation between velocity, gait, and psychosocial context. Species differences were found in mean velocity, “favored” gait, and surface preference. All three species used the walk and the gallop at the slowest and fastest speeds respectively. The macaques and gray langurs walked frequently, but the purple-faced langurs were never seen to do so. At intermediate speeds, the macaques used either the “fast” walk or the “slow” gallop, whereas the gray langurs used irregular patterns of walk-gallop-walk-gallop. The purple-faced langurs were faster (about 20 fps) and less variable than the other species, regardless of distance. These data suggest that motor expression varies among the Cercopithecoid monkeys: the correlation between locomotion and anatomy is not as close as it is among wholly terrestrial or arboreal forms; slowness in the macaque is an expression of social confidence, not of biomechanical inability; high speed in the purple-faced langur is due to psychosocial factors rather than to “terrestrial” adaptability. |
