Limb excursion during quadrupedal walking: how do primates compare to other mammals?

Primate quadrupeds are said to use relatively large limb excursions for mam mals of their body size. Until recently, this claim was based on a comparis on of hindlimb excursion data derived from small samples of primates and no n-primates. Using video recordings collected at zoos and primate research c entres, the present study documents this contrast on much wider samples of quadrupedal mammals. The results indicate that while on average hindlimb ex cursion is relatively larger in quadrupedal primates, this contrast is some what less dramatic than first reports suggested., Comparisons between the d ata reported here and previously collected forelimb excursion data reveal a surprising asymmetry between the fore- and hind excursions for most mammal ian species. Most commonly, forelimb excursion exceeds that of the hindlimb . We suggest that this is related to a complementary asymmetry in limb leng th (forelimbs shorter than hind) for the purpose of achieving equal step le ngths for both pairs of limbs. Relatively large hindlimb excursions in prim ates have been related to a mechanism that reduces stresses on the forelimb s and then recovers mechanical energy during gait. We suggest that large ex cursions of both the fore- and hindlimbs are linked to other alterations in gait parameters, such as step length, contact time, and limb compliance, t hat have been adopted in quadrupedal primates to facilitate locomotion alon g slender arboreal substrates.