Exploring the limits to turning performance with size and shape variation in dogs.

Manoeuvrability, the ability to make rapid changes in direction, is central to animal locomotion. Turning performance may depend on the ability to successfully complete key challenges including: withstanding additional lateral forces, maintaining sufficient friction, lateral leaning during a turn and rotating the body to align with the new heading. We filmed high-speed turning in domestic dogs (Canis lupus familiaris) to quantify turning performance and explore how performance varies with body size and shape. Maximal speed decreased with higher angular velocity, greater centripetal acceleration and smaller turning radii, supporting a force limit for wider turns and a friction limit for sharp turns. Variation in turning ability with size was complex: medium sized dogs produced greater centripetal forces, had relatively higher friction coefficients, and generally aligned the body better with the heading compared with smaller and larger bodied dogs. Body shape also had a complex pattern, with longer forelimbs but shorter hindlimbs being associated with better turning ability. Further, although more crouched forelimbs were associated with an increased ability to realign the body in the direction of movement, more upright hindlimbs were related to greater centripetal and tangential accelerations. Thus, we demonstrate that these biomechanical challenges to turning can vary not only with changes in speed or turning radius, but also with changes in morphology. These results will have significant implications for understanding the link between form and function in locomotory studies, but also in predicting the outcome of predator-prey encounters.