Influence of substrate compliance on wild primate gait kinematics

Influence of substrate compliance on wild primate gait kinematics

Young J W; Dunham N T; McNamara A; Shapiro L J

American Journal of Physical Anthropology

2019

2019-03

The influence of substrate compliance on gait mechanics has received little attention in previous studies of primate locomotion. Using high-speed video, we investigated how free-ranging platyrrhines in lowland Amazonian Ecuador adjust gait kinematics to variation in substrate compliance (N = 789 strides across eight species). We used a force gauge and stiff rope to quantify the compliance (displacement in centimeters per Newton of applied force) of a sample of 200 branches, palm fronds, and lianas representative of locomotor substrates. Substrate type and diameter explained 73% of the variance in compliance, with palms and branches tending to be more compliant than lianas (though the magnitudes of compliance differences varied across the range of diameters). We used this statistical model to estimate the compliance of the substrates utilized in each locomotor stride. The primates in our sample showed a variety of responses to increasing compliance, including decreased speeds (Callicebus, Saguinus, Cebuella) and – controlling for speed – increased stride lengths (Pithecia, Lagothrix), decreased stride frequencies (Callicebus, Pithecia, Lagothrix), increased duty factors (Callicebus), and increases in the average number of supporting limbs during locomotion (Callicebus, Pithecia). Overall, these changes in gait kinematics accord with biomechanical theory predicting that animals moving on compliant substrates can increase stability by reducing impact forces. Other species showed more enigmatic responses to increasing compliance, decreasing duty factors (Ateles) or not significantly adjusting kinematics at all (Alouatta, Saimiri). Overall, our results suggest that substrate compliance should be considered a critical parameter when evaluating primate locomotor performance and locomotor evolution.

Anthropology; Evolutionary Biology

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Journal Article

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Article information provided for research and reference use only. All rights are retained by the journal listed under publisher and/or the creator(s).

277-278

168

NEOMED College of Medicine

Department of Anatomy & Neurobiology; NEOMED Postdoc Publications