Kinematics and Performance Capacity for the Concertina Locomotion of a Snake (Coluber Constrictor)

Abstract

We used a motorized treadmill to determine the endurance (from 4.2 to 5.6 cm s−1) and burst speed of five Coluber constrictor Linnaeus performing concertina locomotion in tunnels 3, 5 and 7 cm wide. The snakes had greatest average endurance at 4.2 cm s−1 within the 5cm wide tunnel (80 min), and the average endurance of snakes moving in the 3 cm tunnel (24 min) was significantly lower than that observed for either the 5 or 7 cm tunnel at the same speed. In contrast to endurance capacity, there was no statistically significant effect of tunnel width on burst speed, and mean values ranged from 13.5 to 16.8 cm s−1 The fastest burst speed observed was 20.8 cm s−1 in a 7 cm tunnel. Analysis of variance on kinematic variables measured from videotapes made of the endurance trials revealed highly significant effects of both speed and tunnel width on kinematics. As the tread speed increased among different endurance trials, the snakes primarily increased the frequency of movements and increased the average forward speed during the moving phase. However, the snakes did not significantly alter either the distance moved per cycle or the proportion of time spent moving in response to different tread speeds used in the endurance trials. Decreased tunnel width caused snakes (1) to move a smaller distance per cycle, (2) to use more regions of static contact with the sides of the tunnel, and (3) to orient the convoluted portions of the body at a smaller angle relative to the sides of the tunnel. Decreased tunnel width did not affect the average forward speed during the moving phase. Hence, tread speed and tunnel width affected different kinematic variables. Significant changes in kinematics did not always cause significant changes in locomotor performance capacity.