Meeting Abstract

119.3  Tuesday, Jan. 7 10:45  Basic Biomechanics of Grizzly Bears: Gaits, speeds and forces. SHINE, C*; ROBBINS, C; KEEN, H; NELSON, O L; MCGOWAN, C P; University of Idaho; Washington State University; Washington State University; Washington State University; University of Idaho shin0453@vandals.uidaho.edu

Bears are the only group of large, plantigrade, quadrupedal mammals in the world. However, they are relatively understudied in the areas of biomechanics and locomotion. This study represents one of the first to investigate the gaits mechanics used by grizzly bears (Ursus arctos horribilis). We used three high speed cameras and a custom built forceplate to record four captive female grizzly bears travelling across a runway across a range of speeds. Video data were analysed to determine the average speed and the gait pattern. The footfall patterns were combined to create an average gait pattern for the bears at each speed. The forceplate data were analysed to determine peak forces and impulses in order to determine fore-hind limb force distribution in each gait. Initial analysis of the video data shows that bears walk with an average speed of 1.7 m/s, use a running walk with an average speed of 2.6 m/s and canter with an average speed of 2.9 m/s. There was no aerial phase for these gaits at any speed recorded. Preliminary results suggest that bears do not appear to trot like other quadrupeds studied, such as dogs and horses, but use a running walk instead. The running walk is the same order of footfalls as a walk but the pattern is changed so that there is a maximum of two feet on the ground at the same time, rather than three. A canter is the preceding gait to a gallop; the stride is extended in the gallop to produce a four beat gait rather than a three beat gait. It is likely that the bears were not achieving a fast enough speed along the runway to break into a full gallop.