Asymmetrical gait of the Saharian rodent Meriones shawi shawi (Duvernoy, 1842) (Rodentia, Mammalia): a high-speed cineradiographic analysis

Abstract

The fast gait of jirds (Meriones shawi shawi) was analyzed by means of high-speed X-ray cinematographic film (500 frames/s). The gait is asymmetrical, related to the transverse gallop with a cycle duration of 0.15 s, for a speed of 1 m∙s−1. The flight phase, which can last for up to 10% of the cycle duration, follows the takeoff of one anterior limb. The kinematics of the hind limb reveal that the angular excursion of the femur is small, but is increased 100% by dorsiflexion (stance phase) and ventroflexion (swing phase) of the vertebral column. During the propulsive moment, the knee joint is stable while the ankle joint opens quickly to a wide angle (70° in 40 ms). The shank joint and the head oscillate vertically, and the relative movements of the anterior and posterior parts of the body create dynamic effects facilitating the cantilevered position of the forequarters during 35% of the cycle. This kinematic analysis reveals that these small mammals differ from large ones in the way they use the geometry of their limbs even when the limbs are moved in a parasagittal plane during fast running.