Meeting Abstract
Animals move in diverse ways, as indicated in part by the wide variety of gaits and modes that have been described for vertebrate locomotion. “Gaits” and “modes of locomotion” both refer to any repeatable pattern of movement of the propulsive structures. Much variation in the gaits of limbed animals is associated with changing speed, whereas different modes of snake locomotion are often associated with moving on different surfaces. For several decades different types of snake locomotion have been categorized as one of four major modes: rectilinear, lateral undulation, sidewinding and concertina. Herein, I highlight some of my work from the last three decades that suggests such a scheme may be overly conservative. For example, during aquatic lateral undulation the timing between muscle activity and lateral bending changes along the length of the snakes, which is unlike terrestrial lateral undulation. Lateral undulation at the edge of a surface while bridging a gap also uses a different motor pattern than lateral undulation on a horizontal surface that supports the entire length of the snake. In all types of concertina locomotion, the distance from the head to the tail changes substantially as snakes alternately flex and then extend different portions of their body. However, snakes climbing with concertina exert forces medially to attain a purchase on the branch, whereas tunnels require pushing laterally to form an anchoring region. Furthermore, different motor patterns are used for these two types of concertina movement. Some snakes climb vertical cylinders with helical wrapping completely around the cylinder, whereas all other forms of concertina bend regions of the body alternately to the left and right. Regardless of the taxonomy that is ultimately favored for categorizing modes of snake locomotion, it should be one that does not obscure important functional differences.
