LOCOMOTOR-ACTIVITY DIFFERENCES BETWEEN SYMPATRIC PATAS MONKEYS (ERYTHROCEBUS-PATAS) AND VERVET MONKEYS (CERCOPITHECUS-AETHIOPS) - IMPLICATIONS FOR THE EVOLUTION OF LONG HINDLIMB LENGTH IN HOMO

Home erectus is notable for its taller stature and longer lower limbs relative to earlier hominids, but the selective pressures favoring suc h long limbs are unclear. Among anthropoid primates, patas monkeys (Er ythrocebus patas) and extant hominids share several extreme characteri stics involved with foraging and movement, including the relatively lo ngest lower limb proportions, longest daily travel distances and large st home ranges for their body or group size, occupancy of some of the driest habitats, and very efficient thermoregulatory systems. We sugge st that patas monkeys are an appropriate behavioral model with which t o speculate on the selective pressures that might have operated on H. erectus to increase lower limb length. Here, in a comparison of the lo comotor activities of patas monkeys and sympatric, closely related ver vet monkeys (Cercopithecus aethiops), we provide evidence for the hypo thesis that patas use their long stride more to increase foraging effi ciency while walking than to run, either from predators or otherwise. (C) 1998 Wiley-Liss, Inc.