The stigmatic-start: a rapid non-planar gait in snakes

Newborn and juvenile yellow anacondas exhibit a previously unreported rapid transient gait, which we term the stigmatic-start. This is characterized by the snake first bending its body and then lifting itself partly out of the plane while moving forward about the mid-section. While superficially similar to sidewinding, the stigmatic-start is qualitatively different as it is a very rapid transient gait that allows the snake to move parallel to itself. To understand our observations, we construct a mathematical model for the non-planar locomotion of snakes that shows an interesting gait transition as a function of body size; small (juvenile) snakes can move via stigmatic locomotion but large (adult) snakes cannot, just as seen. In the context of biomimetic applications, the simulations of our model also suggest an avenue for optimal control of soft active filaments.