Mechanical properties and function of the paw pads of some mammals

Abstract

Unpadded paws would suffer large impact forces when they struck the ground, but paws with elastic pads might be set into oscillation, bouncing up and down before settling on the ground at the beginning of the step. Such oscillations might involve temporary loss of contact with the ground (a phenomenon here called ‘chattering’), making the paw likely to shift its position. Analysis of a simple model reveals the conditions needed to prevent chattering: the paw must not hit the ground too fast and its stiffness must not be too great. Damping can help to prevent chatter. The viscoelastic properties of paw pads from various mammals have been investigated, in dynamic compressive tests, and are discussed in the light of the theoretical model.