Mechanisms enabling cursorial hares to make abrupt turns

Cursorial hares of the genus Lepus are renowned for their athletic abilities but there is limited scientific information on how they achieve abrupt turns and how rapidly they occur. We used digital video footage and images available on public websites, including YouTube, as our data source because of its potential to yield a very large quantity of natural history data, albeit of mostly minimal quality. We searched for videos and still images depicting turns made by hares and we coded postures and actions that occurred during turns. From these visuals, we estimated the angle of change of bearing, and we timed the turns if an on-screen clock was available. The most extreme turn (~ 180°) was made in ~ 0.40 s. Hares under close pursuit effected lesser turns in less time, but those turns usually followed braking. The most abrupt turns involved passive outward yawing of the hindquarters and active inward yawing of the forequarters followed immediately by hindlimb thrust. Hindquarter yawing changes the vector of the ground reaction force, increasing the centripetal component and hence reducing the time taken to effect the turn. We concluded that abrupt turns confer three advantages to cursorial hares under close pursuit: an immediate advantage by decreasing the probability of prehension; a short-term advantage by increasing the distance between the hare and a pursuing predator; and a medium-term advantage by tending to exhaust the predator before the hare itself is exhausted.