Person:
Goldman,
Daniel I.
Publication Search Results
Multi-functional foot use during running in the zebra-tailed lizard (Callisaurus draconoides)
Person:
Goldman,
Daniel I.
1 - 1 of 1
Item
A diversity of animals that run on solid, level, flat, non-slip surfaces appear to bounce on their legs; elastic elements in the limbs
can store and return energy during each step. The mechanics and energetics of running in natural terrain, particularly on surfaces
that can yield and flow under stress, is less understood. The zebra-tailed lizard (Callisaurus draconoides), a small desert
generalist with a large, elongate, tendinous hind foot, runs rapidly across a variety of natural substrates. We use high-speed video
to obtain detailed three-dimensional running kinematics on solid and granular surfaces to reveal how leg, foot and substrate
mechanics contribute to its high locomotor performance. Running at ~10bodylengthss–1 (~1ms–1), the center of mass oscillates
like a spring-mass system on both substrates, with only 15% reduction in stride length on the granular surface. On the solid
surface, a strut-spring model of the hind limb reveals that the hind foot saves ~40% of the mechanical work needed per step,
significant for the lizardʼs small size. On the granular surface, a penetration force model and hypothesized subsurface foot
rotation indicates that the hind foot paddles through fluidized granular medium, and that the energy lost per step during
irreversible deformation of the substrate does not differ from the reduction in the mechanical energy of the center of mass. The
upper hind leg muscles must perform three times as much mechanical work on the granular surface as on the solid surface to
compensate for the greater energy lost within the foot and to the substrate.