Observations on escape runs in wild European hare as a basis for the mechanical concept of extreme cornering with special inference of a role of the peculiar subclavian muscle

Hares are known for their turning performance which is studied here for the first time. The present qualitative analysis of the hare turning technique is based on video recordings of Lepus europaeus being chased by borzoi sighthounds. Movements of body parts, especially of the ears, act like natural accelerometers, allowing as to restore directions of ground reaction forces acting upon each limb. It was established that the major centripetal force is produced by the forelimbs, the inside hindlimb mainly brakes the forward movement, and the thrust produced by the outside hindlimb is vertical with a minor centripetal component. The turn starts from landing of the outside forelimb, which makes a specific lateral kick against the ground. It is performed by means of pronation of the scapula, apparently driven by unique, peculiarly expanded M. subclavius. Thus, the main action in hare turning is non-parasagittal. Surprisingly, the muscular drive of the second (inside) forelimb appears to be the same. Due to the increase in roll-inclination of the body inside the turn, the respective (left or right) M. subclavius produces centripetal ground reaction force in both outside and inside forelimbs. The use of the same muscle in both limbs shows the efficiency of muscular employment in cornering performance of the hare. It was established that the cornering hare combines crabbed (based on yaw) and banked (based on roll) turning techniques -the crabbed turn is used in the first locomotor cycle, then banked turn. The crabbed turn in the first locomotor cycle is performed in two stages: first, during the forelimb support, hindquarters yaw outside, then, during the hindlimb support, forequarters yaw inside. This half-by-half yawing allows to reorient the fore-aft axis of the trunk faster. (C) 2017 Deutsche Gesellschaft filr Saugetierkunde. Published by Elsevier GmbH. All rights reserved.