• Question: why do snakes have no arms or legs

    Asked by chloeexley to Kirsty on 22 Jun 2012.
    • Photo: Kirsty Ross

      Kirsty Ross answered on 22 Jun 2012:

      Snakes have evolved over many, many years. Their ancestors were probably lizard like. As snakes adapted to their environment, they had less and less need for arms and legs. They developed other means of locomotion. Snakes have no arms or legs, yet they can move fairly swiftly through grass, sand, and, in some cases, water, and they can easily climb trees. Snakes can achieve such amazing mobility thanks to well-developed muscles and a row of scales, called ventral scales, on the undersides of their bodies. They usually rely on the ground’s rough surface to provide resistance, something for them to push against that isn’t slippery. Most snakes move by coiling their bodies into a series of S-shaped loops, with each loop pushing against the ground. Some large snakes, like boas, move in a way similar to a caterpillar, inching along the ground. Snakes that live in the desert have a harder time getting the traction necessary for movement. These snakes, called sidewinders, move in a sideways motion that allows them to slither along on the ever-shifting sandy surface.
      While the absence of limbs might seem like a handicap, snakes have certain advantages thanks to their unique bodies. Not only can they move quickly and easily over and through a variety of landscapes, they can also move in near silence, making it easy for them to sneak up on their prey. And their narrow, flexible bodies allow them to fit into small crevices and holes where they can wait for unsuspecting animals to come along (or where they can hide from predators).