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Article
Torque Around the Center of Mass: Dynamic Stability During Quadrupedal Arboreal Locomotion in the Siberian Chipmunk (Tamias sibiricus)
Zoology
  • Andrew R. Lammers, Cleveland State University
  • Ulrich Zurcher, Cleveland State University
Document Type
Article
Publication Date
4-1-2011
Disciplines
Abstract

When animals travel on tree branches, avoiding falls is of paramount importance. Animals swiftly running on a narrow branch must rely on movement to create stability rather than on static methods. We examined how Siberian chipmunks (Tamias sibiricus) remain stable while running on a narrow tree branch trackway. We examined the pitch, yaw, and rolling torques around the center of mass, and hypothesized that within a stride, any angular impulse (torque during step time) acting on the center of mass would be canceled out by an equal and opposite angular impulse. Three chipmunks were videotaped while running on a 2 cm diameter branch trackway. We digitized the videos to estimate center of mass and center of pressure positions throughout the stride. A short region of the trackway was instrumented to measure components of the substrate reaction force. We found that positive and negative pitch angular impulse was by far the greatest in magnitude. The anterior body was pushed dorsally (upward) when the forelimbs landed simultaneously, and then the body pitched in the opposite direction as both hindlimbs simultaneously made contact. There was no considerable difference between yaw and rolling angular impulses, both of which were small and equal between fore- and hindlimbs. Net angular impulses around all three axes were usually greater than or less than zero (not balanced). We conclude that the chipmunks may balance out the torques acting on the center of mass over the course of two or more strides, rather than one stride as we hypothesized.

DOI
10.1016/j.zool.2010.11.004
Version
Postprint
Citation Information
Andrew R. Lammers and Ulrich Zurcher. "Torque Around the Center of Mass: Dynamic Stability During Quadrupedal Arboreal Locomotion in the Siberian Chipmunk (Tamias sibiricus)" Zoology Vol. 114 Iss. 2 (2011) p. 95 - 103
Available at: http://works.bepress.com/ulrich_zurcher/7/